path: root/doc/Vdebug.txt

*Vdebug*   A powerful, fast, multi-language debugger for Vim


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===============================================================================
CONTENTS                                                      *Vdebug-contents*

    1. Introduction..................................|VdebugIntro|
        1.1 Debugging................................|VdebugIntroDebugging|
        1.2 The DBGP protocol........................|VdebugIntroDBGP|
        1.3 Supported languages......................|VdebugIntroLanguages|
    2. Installing the plugin.........................|VdebugInstallation|
    3. Setting up the debugging environment..........|VdebugSetUp|
        3.1 PHP set up...............................|VdebugSetUpPHP|
        3.2 Python set up............................|VdebugSetUpPython|
        3.3 Ruby set up..............................|VdebugSetUpRuby|
        3.4 Perl set up..............................|VdebugSetUpPerl|
        3.5 NodeJS set up............................|VdebugSetUpNodejs|
        3.6 TCL/Wish set up..........................|VdebugSetUpTcl|
    4. Usage.........................................|VdebugUsage|
        4.1 Starting the debugger....................|VdebugStart|
        4.2 Finding your way around the UI...........|VdebugUI|
            4.2.1 The source window..................|VdebugSourceWindow|
            4.2.2 The watch window...................|VdebugWatchWindow|
            4.2.3 The stack window...................|VdebugStackWindow|
            4.2.4 The status window..................|VdebugStatusWindow|
            4.2.5 The breakpoint window..............|VdebugBreakpointWindow|
            4.2.6 The log window.....................|VdebugLogWindow|
        4.3 Commands.................................|VdebugCommands|
            4.3.1 Run................................|VdebugCommandRun|
            4.3.2 Step over..........................|VdebugCommandStepOver|
            4.3.3 Step in............................|VdebugCommandStepIn|
            4.3.4 Step out...........................|VdebugCommandStepOut|
            4.3.5 Run to cursor......................|VdebugCommandRunToCursor|
            4.3.6 Detach.............................|VdebugCommandDetach|
            4.3.7 Stop/close.........................|VdebugCommandStop|
        4.4 Breakpoints..............................|VdebugBreakpoints|
            4.4.1 Setting a line breakpoint..........|VdebugSetLineBreakpoint|
            4.4.2 Setting other breakpoints..........|VdebugSetBreakpoints|
            4.4.3 Viewing your breakpoints...........|VdebugViewBreakpoints|
            4.4.4 Removing breakpoints...............|VdebugRemoveBreakpoints|
        4.5 Evaluating code..........................|VdebugEval|
            4.5.1 Evaluating any expression..........|VdebugEvalExpression|
            4.5.2 Evaluating highlighted expressions.|VdebugEvalHighlighted|
            4.5.3 Evaluating variable under cursor   |VdebugEvalUnderCursor|
    5. Options.......................................|VdebugOptions|
        5.1 Quickly setting options..................|VdebugOpt|
        5.2 List of options..........................|VdebugOptionList|
    6. Key maps......................................|VdebugKeys|
    7. Setting debugger features.....................|VdebugFeatures|
    8. Using an IDE key..............................|VdebugIDEKey|
    9. Debugging a script on a remote server.........|VdebugRemote|
        9.1 File path mapping........................|VdebugRemoteFilePaths|
        9.2 Connecting the two machines..............|VdebugRemoteConnection|
    10. Troubleshooting..............................|VdebugTroubleshooting|
    11. Acknowledgements.............................|VdebugAcknowledgements|

==============================================================================
1. Introduction                                                  *VdebugIntro*

So what does this plugin actually do? 

It provides an interface for debugging scripts, allowing you to halt execution,
view the variables at the current position and find out exactly what's going on
in your program. It supports the DBGP protocol, which includes all types of 
breakpoint, code snippet evaluation, and more.

------------------------------------------------------------------------------
1.1 Debugging                                           *VdebugIntroDebugging*

Debugging is mainly used to do what the name suggests: weed out bugs that are
appearing in your program. Using a debugging tool means that you don't have to
resort to 'print' statements or writing out to logs to find out where your
program is going wrong: you can pause execution, step through line by line and
break at certain points to see what's going on.

This is nothing new, and IDEs have been supporting debuggers for many years. In
fact, Vim has had several plugins that support debuggers, most notably the long
line of related Xdebug plugins for PHP.

So why have I created a new one? There are a few reasons:

    * The Xdebug plugin was getting too complicated, and all the code was in
      one file, making it difficult to navigate and maintain.
    * It wasn't truly multi-language, and was mainly focussed on Xdebug with
      PHP. I wanted a debugger that could work identically with any language
      that had debuggers using the DBGP protocol.
    * There were some inefficiencies in the Xdebug plugin that affected the
      speed, which I knew could be addressed.
    * I wanted to create a set of Python classes that could be used on their
      own outside of Vim, that provided an interface to debuggers.
    * There were extra features that I wanted to build in, and doing so in the
      original plugin would have meant a rewrite anyway.

I hope you find this plugin helpful and enjoyable to use :)

------------------------------------------------------------------------------
1.2 The DBGP protocol                                        *VdebugIntroDBGP*

This is a protocol that defines the communication between an IDE and debugger
engine. The IDE speaks to the engine in pre-defined plain text commands, such
as: >

    breakpoint_set -i 10 -t line -f /home/user/example.php -n 5
<
The debugger engine replies in XML, such as: >

    <response command="breakpoint_set"
          transaction_id="10"
          state="enabled"
          id="1"/>
<
That makes the protocol cross platform and pretty easy to implement. One of the
Python modules (files), called 'dbgp.py', is a set of classes that provide
socket handling and a object-oriented interface to the most common operations.

For a complete description of the DBGP protocol visit:
 http://xdebug.org/docs-dbgp.php

------------------------------------------------------------------------------
1.3 Supported languages                                 *VdebugIntroLanguages*

Technically, supported languages include any that have a debugging engine that
uses the DBGP protocol. This plugin was designed with four languages in mind,
PHP, Python, Ruby and Perl. These have all been tested with this plugin. For
information on how to configure the environment with each of these languages
see section 3, |VdebugSetUp|.

==============================================================================
2. Installing the plugin                                  *VdebugInstallation*

Please note that you must have VIM 7+ for this plugin to work, and it must be
compiled with tabs, signs and Python support. If you're using Windows, some
reports have said that Python must be installed separately to allow VIM to use
it.

The Github page for the plugin is https://github.com/joonty/vdebug, and the VIM
scripts URL is http://www.vim.org/scripts/script.php?script_id=4170.

By far the easiest way to install is by using a plugin manager, e.g. vundle
(https://github.com/gmarik/vundle/) or pathogen 
(https://github.com/tpope/vim-pathogen.git). If you have one of these, follow
the normal installation procedure.

If you aren't using a plugin manager, you have to do it the long way. Either
clone the Github repository or download the ZIP from VIM scripts.

Move the contents of each folder in the plugin (e.g. syntax/, plugin/) into 
the corresponding folder in your VIM home directory - create the directories 
if they don't exist. The VIM home directory is: >
    $HOME/.vim
<
on Linux/Unix, or: >
    %USERPROFILE%\vimfiles
<
on Windows. The %USERPROFILE% directory on Windows is usually: >
    C:\Users\[User name]\
<
or: >
    C:\Documents and Settings\[User name]\
<

You may also use the system plugin directory for VIM on your system if you want 
to install for all users. 

==============================================================================
3. Setting up the debugging environment                          *VdebugSetUp*

This section looks at setting up the debugger engine to allow Vdebug to
communicate with it during execution. The set-up varies depending on the
language and operating system, and I can't possibly list all combinations here.
What I will do is explain how I set it up for each language on my Linux system
(Ubuntu 12.04), and hopefully that will give enough information for you to be
able to apply it to your circumstance.

------------------------------------------------------------------------------
3.1 PHP set up                                                *VdebugSetUpPHP*

The most popular DBGP debugger for PHP is Xdebug.

I find that the most effective way to install Xdebug is to use PECL, instead
of a OS-level package manager such as aptitude or yum. You can also compile it
from source if you're feeling hardy. To install it via PECL, run this from a
command line (requires root/admin privileges): >

    pecl install xdebug
<
When this finishes, it will tell you about a library (.so on *nix, .dll on
Windows) that needs to be included. Copy down the file path, as we need to add
it as a zend extension. This can be done in the PHP INI file, but in Ubuntu 
I can add a new file to /etc/php5/conf.d/ that contains all the configuration 
options and gets loaded automatically by PHP.

Add these options to the INI file: >

    zend_extension=/path/to/xdebug.so
    xdebug.remote_enable=on
    xdebug.remote_handler=dbgp
    xdebug.remote_host=localhost
    xdebug.remote_port=9000
<
If using Apache, restart it to enable the new library. The command line
interface should be ready to go - type "php -v" and you should see the line >
    with Xdebug v2.2.0, Copyright (c) 2002-2012, by Derick Rethans
<
or something similar (version may differ). You are technically ready to go, but
there's one extra step that I like to do to make command line debugging nice
and quick. I create a bash script called "php-xdebug", which automatically
starts the debugger engine. The script looks like this (unix only): >

#!/bin/bash
export XDEBUG_CONFIG="idekey=xdebug"
/usr/bin/php "$@"
<
Run "chmod +x" on the file and put it somewhere in your $PATH list, and you can
then use this instead of php when debugging. For instance, instead of "php
myscript.php", run "php-xdebug myscript.php" to start the debugger session.

You are now officially ready to start debugging with PHP. However, if you've
become unstuck at any point then there are plenty of Google tutorials on
setting up Xdebug, or you can email me and I'll do my best to help.

------------------------------------------------------------------------------
3.2 Python set up                                          *VdebugSetUpPython*

Python has an standalone debugging tool that you can use from the command line,
but to use Vdebug in conjunction with your Python scripts you will have to grab
the "pydbgp" tool, created by ActiveState (who make the Komodo Edit/IDE
software).

To do this, go to http://code.activestate.com/komodo/remotedebugging/,
download the Python client for your OS and extract it.

Inside this package is a binary file called pydbgp that we can include when
running a script, which will allow for remote debugging. If you're using
version 8 or greater, then you will need to move the dbgp directory, which is
inside pythonlib, to the same directory that contains the pydbgp executable.
If you don't do this then you will get an error saying "No module named
dbgp.client".

To debug a script called "myscript.py", run the following: >
    python -S path/to/pydbgp -d localhost:9000 myscript.py
<
adding in the path to the pydbgp binary file. Running it without starting
Vdebug will give an error saying that it can't connect to the host. If you see
this, you're ready to go.

NOTE: You may have a problem when trying to do an "eval". If you get an error
mentioning something about not providing a length then you need to patch the
client.py file in the Python remote debugger source code. I've created a patch 
that you can get at https://gist.github.com/3348076. It will only apply cleanly
if it's for the same version as the package you downloaded. 

If using unix you can use the `patch` command to apply the changes, e.g: >

    patch dbgp/client.py < client-7.1.0.patch
<
If you're still having trouble, drop me an email.

------------------------------------------------------------------------------
3.3 Ruby set up                                              *VdebugSetUpRuby*

Like Python, Ruby has an standalone debugging tool that you can use from the 
command line, but to use Vdebug in conjunction with your Ruby scripts you will 
have to get the "rdbgp.rb" script that comes bundled with Komodo Edit/IDE by
Activestate.

Get the latest Komodo IDE from
http://downloads.activestate.com/Komodo/releases/ (e.g. version 7.1.1), and
unpack it. There's a script called rdbgp.rb, which, in the linux version, is
located at INSTALLDIR/lib/support/dbgp/rubylib/. This script needs to be
included when debugging another script remotely.

To start debugging, you need to set two environment variables: one for the
location of the directory containing the rdbgp.rb script and one for settings
used by the debugger: >
    export RUBYDB_LIB=path/to/rubylib/
    export RUBYDB_OPTS="HOST=localhost PORT=9000"
<
For example, if we want to debug a Ruby script called "myscript.rb", run the
following from the command line: >
    export RUBYDB_LIB=~/KomodoIDE/INSTALLDIR/lib/support/dbgp/rubylib
    export RUBYDB_OPTS="HOST=localhost PORT=9000"
    ruby -I$RUBYDB_LIB -r $RUBYDB_LIB/rdbgp.rb myscript.rb
<
Change the environment variables to suit your set-up and you will be ready to
go.

NOTE: You may have a problem when changing context in the watch window. If you
get a long error message when switching to globals, for instance, you will need
to patch your commands/context.rb file in the rubylib directory. I've created a
patch that you can get at https://gist.github.com/3347567 - if using unix you
can use the patch command to apply it, e.g: >

    patch rubylib/commands/context.rb < context.patch
<
If you're still having trouble, drop me an email.

------------------------------------------------------------------------------
3.4 Perl set up                                              *VdebugSetUpPerl*

Perl is one of the trickier languages to set up, unless you have very specific 
instructions on what to do. Fortunately, that's what I'm going to give you!

Like Python and Ruby, Activestate provide a standalone module that you can use 
to remotely debug Perl applications. What makes this more difficult than Python
and Ruby is that the debugging script changes and, as far as I can see, breaks
after a particular version. That means you have to get the right version from
Activestate, and working that out on your own is a bit of a pain.

Fortunately, I'm going to make it easy for you and give you the exact version
to download. Go to the archive at 
http://downloads.activestate.com/Komodo/releases/archive/4.x/4.4.1/remotedebugging 
and download the archive with "Perl" in the name that suits your operating system.

Just a reminder that, from here, the instructions are for Linux. Activestate
have instructions for other systems on their website.

Unpack the archive somewhere on your system. There is a perl5db.pl script that 
you will need to include to enable debugging. To do this you need to set some 
environment variables to point to the directory containing this file: >
    export PERL5LIB=/path/to/Komodo-PerlRemoteDebugging-xxx/
    export PERL5DB="BEGIN { require q($PERL5LIB/perl5db.pl)}"
    export PERLDB_OPTS="RemotePort=localhost:9000"
    export DBGP_IDEKEY="whatever"
<
The second line is for good measure, making sure the right file is included
when perl starts up. The third line sets debugger options, and the fourth line
allows you to set an IDE key if you want to use one (Vdebug allows you to
restrict connections to a single IDE key, but by default all connections will
be picked up - see section |VdebugIDEKey|).

To start a Perl script with the debugger engine activated, e.g. myscript.pl,
run: >
    perl -d myscript.pl
<
If you haven't started Vdebug you will get a message saying that it can't
connect. This means you've set it up correctly.

------------------------------------------------------------------------------
3.5 NodeJS set up                                          *VdebugSetUpNodejs*

NodeJS is the easiest language to set up for debugging with Vdebug, as
Activestate have made the debugger engine available through npm. All you need
to do is run: >
    npm install komodo-debug -g
<

You can then begin a debug session by starting Vdebug and running: >
    node-dbgp -h 127.0.0.1 -p 9000 myscript.js
<
Where the 'h' option specifies the address that Vdebug is listening on, and 'p'
is the port.

------------------------------------------------------------------------------
3.6 TCL/Wish set up                                           *VdebugSetUpTcl*

Like Python and Ruby, Tcl and Wish have an standalone debugging tool that you 
can use from the command line, which has again been made available by 
ActiveState.

Go to http://code.activestate.com/komodo/remotedebugging/, download the Tcl 
client for your OS and extract it. Inside this package is a binary file called 
dbgp_tcldebug that we will use instead of the tcl/wish binary. It accepts the
script as an option, along with the vdebug server address and port.

If we want to debug a Tcl script called "myscript.tcl", start Vdebug listening
and run the following: >
    path/to/dbgp_tcldebug -dbgp localhost:9000 -app-file myscript.tcl \
        -app-shell /usr/bin/tcl
<
To debug a wish script called "mywishscript.tcl", run the following: >
    path/to/dbgp_tcldebug -dbgp localhost:9000 -app-file mywishscript.tcl \
        -app-shell /usr/bin/wish
<
Note that the only difference is the app shell argument. 

There is a known error with using "tix", however, as it appears that Activestate's
debugger engine doesn't support it.

==============================================================================
4. Usage                                                         *VdebugUsage*

This section deals with how to use Vdebug to debug a script. It assumes that
you've already set up the debugger with the language that you're using: if you
haven't see |VdebugSetUp|.

------------------------------------------------------------------------------
4.1 Starting the debugger                                        *VdebugStart*

The default key for starting the debugger is <F5>. Pressing this should show
the message: >
    Waiting for a connection (this message will self-destruct in 30 seconds...)
<
(If you don't get this message see the section on troubleshooting,
|VdebugTroubleshooting|)

Vdebug is now listening for an incoming connection, which will be started when
a script is run with the debugger engine activated. View the section
|VdebugSetUp| to see the necessary steps to start a script in this way. It will
be obvious when a connection is made, because a new VIM tab opens with four
windows, signalling the start of a new debugging session.

If you are starting a script but Vdebug does not react, see the
|VdebugTroubleshooting| section for information.

The debugger will pause at the first line of the beginning of the script. It
then waits for your action before continuing.

------------------------------------------------------------------------------
4.2 Finding your way around the UI                                  *VdebugUI*

Now that you are in debug mode you will see 4 windows. The far left window
shows the file at the current point of execution, |VdebugSourceWindow|. The top
right window is the watch window, showing the variables at the current context,
|VdebugWatchWindow|. The middle right window shows the stack, or the trace, up
to that point in the script, |VdebugStackWindow|. The bottom right window shows
the current debugger status, connection details and a help message.

------------------------------------------------------------------------------
4.2.1 The source window                                   *VdebugSourceWindow*

This shows the current position of the debugger. The file will automatically
change as the debugger pauses in different parts of the code, and the current
line is shown with a "->" sign in the margin.

Don't edit the contents of the file when in debug mode, and especially don't 
edit without saving - this causes problems when swapping between files.

You can set line breakpoints here with the <F10> key or :Breakpoint, and can
tell the debugger to run to the cursor with <F9>.

------------------------------------------------------------------------------
4.2.2 The watch window                                     *VdebugWatchWindow*

The watch window shows the variables at the current position in execution. The
variable name, type, length (if applicable) and value are shown. They are shown
as a tree, because arrays/lists and objects have children. Hopefully it's
fairly self-explanatory: right arrows show a closed tree, down arrows show an
open tree and diamonds show variables that don't have children. These markers
can be customised (see |VdebugOptions|), and will fall back to ASCII equivalents
if multi byte support is not enabled in the VIM configuration.

To open a closed tree, navigate to a line with a closed tree (right arrow) and
press <enter> (<cr>) or double-click if you have mouse-support enabled. This 
will open the tree, and show all the children.

There are two style options for the watch window: expanded (default) and compact.
The expanded version has a new line between each variable, and uses separator
strings to indicate relationships. The compact version has a variable on each
line, and works better for smaller screens. To set this option, see 
|VdebugOptions-watch_window_style|.

The watch window automatically updates every time the debugger pauses, so
nothing needs to be done on your part.

You can also see variables from different contexts. For example, PHP has normal
context variables and global variables, and the debugging engine differentiates
between them. The options are shown in a sort of tab interface at the top of
the watch window, and you can switch to a different context by pressing <enter>
(<cr>) on the context you want, or double-clicking on it with your mouse if you
have mouse support enabled. The currently showing context is highlighted (if
you have syntax highlighting on) and starts with an asterisk (*).

The watch window is also used to show the results of "eval" operations. See
the |VdebugEval| section for more on that. After evaluating an expression you
can return to the variable context with <F11> (default).

------------------------------------------------------------------------------
4.2.3 The stack window                                     *VdebugStackWindow*

The stack window shows the current execution stack, which is a list of files
and functions/methods that the program has run through to get to the current
position. The top entry ([0]) is always the current position, and the entries
below show the path the script has taken.

Like the watch window, the stack will update automatically every time the 
debugger pauses. You can jump to a place in the stack by putting your cursor
over a line and pressing <enter> (<cr>) or by double clicking with your mouse
(if you have mouse support enabled).

------------------------------------------------------------------------------
4.2.4 The status window                                   *VdebugStatusWindow*

The status window shows several things. At the top of the window it shows the
debugger's status, which is a message the engine sends to Vdebug. It will say
when it's starting, running, breaking or stopping.

The two lines below show the connection details. The first of these lines show
which address and port Vdebug is binding itself to (defaults to localhost:9000)
and the second shows the address and port that the engine has used to connect.
If you're debugging a script on your machine then the IP address will be the
same as localhost. It's only when you're debugging a script on a remote server
that it will be any different. However, the port used will be, to all intents
and purposes, random.

The bottom line is just a helpful message, reminding you how to start and where
to go for help!

------------------------------------------------------------------------------
4.2.5 The breakpoint window                           *VdebugBreakpointWindow*

This is a bit of an odd one out, as it doesn't show by default and can be
summoned at will. It lists all the breakpoints that have been set, and shows
the IDs that can be used to remove them.

To open the window use the command :BreakpointWindow. It's in a table format,
so hopefully it won't need any more explanation. To close the window again,
just re-type :BreakpointWindow or :q.

To see more about breakpoints see |VdebugBreakpoints|.

------------------------------------------------------------------------------
4.2.6 The log window                                         *VdebugLogWindow*

Another odd one out, this only appears in two situations:
    1. You have the "debug_window_level" option set to >= 1
    2. An error occurs

In the case of 1), the window will open as soon as a debugging session starts.
This isn't recommended for normal use, as it noticeably slows the interface
down. In the case of 2), the window will automatically open when an error happens.

If you want to log things, it's better to use file logging (see
|VdebugLogFile|).

------------------------------------------------------------------------------
4.3 Commands                                                  *VdebugCommands*

This section will describe the basic commands that you will need to start
debugging, and the default keys mapped to those commands.

    4.3.1 Run                                               *VdebugCommandRun*
    Default key: <F5>
    Tells the debugger engine to run, which it will do until it meets a
    breakpoint or the end of the script.

    4.3.2 Step over                                    *VdebugCommandStepOver*
    Default key: <F2>
    Tells the debugger engine to step to the next statement, e.g. the next line
    of the script. Useful for going through a problem section of the script
    with a fine toothcomb.
    
    4.3.3 Step in                                        *VdebugCommandStepIn*
    Default key: <F3>
    Tells the debugger engine to step into a statement on the current line.
    For instance, if there's a function call on the current line it will jump to
    the start of that function.
    
    4.3.4 Step out                                      *VdebugCommandStepOut*
    Default key: <F4>
    Tells the debugger engine to step out of the current statement into the
    calling statement. Essentially this is the opposite of step in.

    4.3.5 Run to cursor                             *VdebugCommandRunToCursor*
    Default key: <F9>
    Tells the debugger engine to run until the point where the cursor is
    currently sitting. One of the most useful commands, as it means that
    setting a hard breakpoint is not always necessary. This only works if the
    cursor is in the source window, otherwise it doesn't make sense! But it
    also doesn't need to be a point in the current file, just somewhere that 
    the execution is going to hit.

    4.3.6 Detach                                         *VdebugCommandDetach*
    Default key: <F7>
    Tells the debugger engine to break away and continue execution as normal.
    At this point, breakpoints are forgotten and Vdebug doesn't have any more
    control over execution. An alternative to "stop", which kills the program.

    4.3.7 Stop/close                                       *VdebugCommandStop*
    Default key: <F6>
    Tells the debugger engine to stop the program, killing it at the point it's
    reached. If the program has already been stopped it closes the debugger UI.

------------------------------------------------------------------------------
4.4 Breakpoints                                            *VdebugBreakpoints*

This section explains how to set and remove line breakpoints, and also how to
set more advanced types of breakpoint. It also explains how to manage your list
of breakpoints.

There are several types of breakpoint, and their support varies between
debugger engines. The breakpoint types are:

    * Line: break at a line in a given file
    * Conditional: break at a line in a file when a given condition is true
    * Exception: break when a given exception is thrown
    * Call: break when a given function is called
    * Return: break when returning from a given function
    * Watch: break when a variable or address is written

------------------------------------------------------------------------------
4.4.1 Setting a line breakpoint                      *VdebugSetLineBreakpoint*

This is the simplest kind of breakpoint to set, as it can be done in a single
button press. The reason for this is that it is visual: put the cursor over the
line and activate the breakpoint - all the work is then done to tell the
debugger to break at this file and line number.

To set a breakpoint, make sure you're in the source window and place the VIM
cursor over the line you want to break at. Press <F10> to set a line breakpoint,
or type :Breakpoint. The line is then highlighted. To remove the breakpoint
just repeat the action on the same line.

------------------------------------------------------------------------------
4.4.2 Setting other breakpoints                         *VdebugSetBreakpoints*

You can set any type of breakpoint using the :Breakpoint command. The syntax
is: >
    :Breakpoint <type> <arguments>
<
Using :Breakpoint without any arguments sets a line breakpoint at the current
cursor position.

The options for type are:

    * line
    * conditional
    * exception
    * return
    * call
    * watch

Each type has its own interpretation of the following arguments. The "line"
type breakpoint is covered in the previous section, |VdebugSetLineBreakpoint|.

:Breakpoint conditional <condition>          *VdebugSetBreakpoints-conditional*
    Extends the line breakpoint. Sets a breakpoint on the current file and
    line, but only if <condition> evaluates to true. Everything after
    'conditional' is treated as the condition, and it must be valid code in the
    current language. E.g: >

    :Breakpoint conditional $x == 2
<

:Breakpoint exception <exception-name>         *VdebugSetBreakpoints-exception*
    Sets a breakpoint to activate when an exception is thrown. The full name of
    the exception should be provided. E.g: >

    :Breakpoint exception PDOException
<

:Breakpoint call <function-name>                    *VdebugSetBreakpoints-call*
    Sets a breakpoint to activate when a function is called. The debugger stops
    at the first line of the function. Note that the syntax for <function-name>
    varies between debugger engine and is NOT well documented. In fact, Xdebug
    doesn't mention how to set a breakpoint on class/object methods, and I have
    had limited success in doing so. Global functions work without a problem, 
    e.g: >
    
    :Breakpoint call open_file 
<
    In PHP, it seems that you need to use static method syntax to break at
    methods, even if the method isn't static. If I have a class called Foo and
    a method on it called bar(), I would use: >

    :Breakpoint call Foo::bar
<
    This seems to work, but I'm not guaranteeing it!

:Breakpoint return <function-name>                *VdebugSetBreakpoints-return*
    Sets a breakpoint to activate when a function returns. The debugger stops
    at the return line of the function. Note that this suffers from the same
    problem as <call>, and setting class/object methods may not be possible.
    Read the call documentation for more on that. However, global functions 
    work without a problem. E.g: >
    
    :Breakpoint return open_file 
<

:Breakpoint watch <variable-or-address>            *VdebugSetBreakpoints-watch*
    Sets a breakpoint to activate when a variable or address is written. This
    is not supported by Xdebug, so don't get your hopes up. Still, if it did
    work then it might look like this: >
    
    :Breakpoint watch $myvar
<

------------------------------------------------------------------------------
4.4.3 Viewing your breakpoints                         *VdebugViewBreakpoints*

To see your current list of breakpoints, use the :BreakpointWindow command to
open a window showing a tabular list. You can read more about it at
|VdebugBreakpointWindow|.

------------------------------------------------------------------------------
4.4.4 Removing breakpoints                           *VdebugRemoveBreakpoints*

Line breakpoints can be removed by pressing <F10> (default) or :Breakpoint while
on a line with an existing breakpoint. Other types of breakpoint can be removed
using the command: >
    :BreakpointRemove <id>
<
The breakpoint's ID can be found in the breakpoint window (see
|VdebugBreakpointWindow|), in the first column. For example: >
    :BreakpointRemove 11000
<
To remove all breakpoints in one go use the command: >
    :BreakpointRemove *
<

------------------------------------------------------------------------------
4.5 Evaluating code                                               *VdebugEval*

You can evaluate code snippets at the current point of execution, which can be
used to see the result of a condition, arithmetic expressions, etc. These
snippets are written in the language that's being debugged. There are two ways
of evaluating expressions: you can either write them yourself
(|VdebugEvalExpression|) or use visual highlighting to select an expression from
the source window.

On evaluating an expression, the result is shown in the watch window. To return
back to the context view, press <F11> (default).

------------------------------------------------------------------------------
4.5.1 Evaluating any expression                         *VdebugEvalExpression*

To evaluate an expression, use the command :VdebugEval: >
    :VdebugEval <code>
<

The result is shown on the watch window. E.g: >
    :VdebugEval $x + 2
<

------------------------------------------------------------------------------
4.5.2 Evaluating highlighted expressions               *VdebugEvalHighlighted*

Use visual highlighting (default command "v") to select an expression that you
want to evaluate and type "<Leader>e" (leader key followed by the letter "e"). 
The result of the evaluation is shown on the watch window.

------------------------------------------------------------------------------
4.5.3 Evaluating the variable under cursor             *VdebugEvalUnderCursor*

You can evaluate the variable under the cursor in the watch window with <F12>
(default key). Note that only variables before the current line will have a
value, and trying to evaluate uninitialized variables may cause an error with
some debugger engines.

==============================================================================
5. Options                                                     *VdebugOptions*

There are two ways of setting options for Vdebug. The options are stored in a 
Vim dictionary (the equivalent of an associative array in PHP or a hash in Ruby). 
This dictionary can be modified using the global variable "g:vdebug_options".
However, as you may want to change options on the fly, a command (:VdebugOpt) 
has been added for your convenience so that you can easily get and set options 
without having to use Vim dictionary syntax.

I've found that the best way of setting options is to use the dictionary in your
vimrc file and the :VdebugOpt command when you want to set options on the fly.

------------------------------------------------------------------------------
5.1 Quickly setting options with :VdebugOpt                        *VdebugOpt*

The VdebugOpt command takes one or two arguments: one if you want to retrieve
the value of an option, and two if you want to set the option to a new value.
The first argument autocompletes with a list of options, and the second argument
will autocomplete to the current value, if set. Here are some examples: >

    :VdebugOpt server " Prints the current value
    :VdebugOpt continuous_mode 0 "Sets to 0
    :VdebugOpt debug_file /home/jon/vdebug.log
<
Note that using :VdebugOpt only sets the value of the option for the time that
your vim session is open. As soon as you close it they will be forgotten, so
retain option settings by adding them to your vimrc.

------------------------------------------------------------------------------
5.2 List of options                                         *VdebugOptionList*

The default options look like this: >
    let g:vdebug_options= {
    \    "port" : 9000,
    \    "server" : 'localhost',
    \    "timeout" : 20,
    \    "on_close" : 'detach',
    \    "break_on_open" : 1,
    \    "ide_key" : '',
    \    "path_maps" : {},
    \    "debug_window_level" : 0,
    \    "debug_file_level" : 0,
    \    "debug_file" : "",
    \    "watch_window_style" : 'expanded',
    \    "marker_default" : '⬦',
    \    "marker_closed_tree" : '▸',
    \    "marker_open_tree" : '▾'
    \}
<
You can either use the multi-line notation like above, or set individual keys:
>
    g:vdebug_options['port'] = 9001
<
You only need to set the options you want to change: the defaults will be used
if you don't set them.

Here is a list of all the available options.

                                                          *VdebugOptions-port*
g:vdebug_options["port"] (default = 9000)                 
    This sets the port that Vdebug will use to listen for connections. Xdebug
    defaults to 9000, and it's the normal port for DBGP, so only change it if
    you also change the port that the engine uses.

                                                        *VdebugOptions-server*
g:vdebug_options["server"] (default = "localhost")      
    Sets the address that Vdebug will use to listen for connections. It
    defaults to localhost, as it assumes that the debugger engine will be
    running on the same machine and also connecting to localhost. If you want
    to debug a script on a different machine, look at |VdebugRemote|.

                                                       *VdebugOptions-timeout*
g:vdebug_options["timeout"] (default = 20)             
    Number of seconds to wait for when listening for a connection. VIM will
    lock up due to the server socket listening for a client connection, so this
    timeout is there to protect your VIM from locking up forever!

                                                      *VdebugOptions-on_close*
g:vdebug_options["on_close"] (default = "detach")     
    The default action when stopping the debugger. By default, it will detach
    the debugger engine meaning that the script will execute until it finishes.
    The other option is "stop", which means that the script will be killed
    immediately.

                                                 *VdebugOptions-break_on_open*
g:vdebug_options["break_on_open"] (default = 1)     
    This determines whether the debugger should stop on the first line of the
    script, or just immediately start running until it hits a pre-defined
    breakpoint.

                                                       *VdebugOptions-ide_key*
g:vdebug_options["ide_key"] (default = empty)          
    The IDE key that Vdebug will watch for with incoming connections. This
    allows you to differentiate between connections, and only start a session
    when this key matches the incoming key. This is empty by default, which
    means that any incoming connection will be accepted. Filling in a value
    restricts the connections to those that have a matching key. See
    |VdebugIDEKey| for more information.

                                                       *VdebugOptions-path_maps*
g:vdebug_options["path_maps"] (default = {})          
    This is only used for debugging a script on a remote machine. This is used
    to map remote file paths to local file paths, as they are very likely to be
    different. This is a VimL dictionary of mappings between remote files (keys)
    and local files (values).

                                            *VdebugOptions-debug_window_level*
g:vdebug_options["debug_window_level"] (default = 0)    
    Sets the amount of information sent to the log window, |VdebugLogWindow|.
    The default value, 0, only shows errors. The other options are 1
    (information) and 2 (debug). The latter option is not ideal to use, as it
    noticeably slows down the interface due to the amount of window writes.
    It's far better to use file logging (|VdebugOptions-debug_file_level|) for
    debugging.

                                              *VdebugOptions-debug_file_level*
g:vdebug_options["debug_file_level"] (default = 0)    
    Sets the amount of information written to the log file, which is set with
    the |VdebugOptions-debug_file| option. The default value, 0, only shows 
    errors. The other options are 1 (information) and 2 (debug).

                                                    *VdebugOptions-debug_file*
g:vdebug_options["debug_file"] (default = empty)    
    Sets the path to the log file, which writes information set by
    |VdebugOptions-debug_file_level|. This is empty by default, meaning that
    file logging is turned off. Enter a file path to enable file logging.

                                            *VdebugOptions-watch_window_style*
g:vdebug_options["watch_window_style"] (default = 'expanded')    
    Sets the style of the watch window, 'expanded' or 'compact'. The compact
    version works better for smaller screens, but the expanded version looks
    a bit nicer in my opinion.

                                                *VdebugOptions-marker_default*
g:vdebug_options["marker_default"] (default = '⬦')    
    Sets the marker used for a variable in the watch window that has no
    children. A "*" symbol is used if multi byte support is not enabled.

                                            *VdebugOptions-marker_closed_tree*
g:vdebug_options["marker_closed_tree"] (default = '▸')    
    Sets the marker used for a variable in the watch window that does have
    children, but the tree is currently closed. A "+" symbol is used if multi 
    byte support is not enabled.

                                              *VdebugOptions-marker_open_tree*
g:vdebug_options["marker_open_tree"] (default = '▾')    
    Sets the marker used for a variable in the watch window that does have
    children, and the tree is currently open. A "-" symbol is used if multi 
    byte support is not enabled.

                                              *VdebugOptions-continuous_mode*
g:vdebug_options["continuous_mode"] (default = 0)    
    If enabled, Vdebug will start listening immediately after a debugging 
    session has finished, allowing for constant debugging across separate
    requests. Press <F6> during a debugging session to stop this, or <Ctrl-C>
    when Vdebug is listening.

==============================================================================
6. Key maps                                                       *VdebugKeys*

By default, function keys are mapped to execute debugger commands. However, I'm
aware that people may already have them mapped to something else, so would like
to change the default behaviour. Before you do that, be aware that Vdebug only
maps two commands outside of the debugger mode, "run" and "set_breakpoint". All
others are mapped only when Vdebug starts up, and unmapped when it shuts down.
Not only this, but any commands that you have already mapped to these keys will
be remembered and restored when you come out of debugging mode.

If you would still like to remap the default keys, this is possible using the 
key map dictionary, g:vdebug_keymap: >

    let g:vdebug_keymap = {
    \    "run" : "<F5>",
    \    "run_to_cursor" : "<F1>",
    \    "step_over" : "<F2>",
    \    "step_into" : "<F3>",
    \    "step_out" : "<F4>",
    \    "close" : "<F6>",
    \    "detach" : "<F7>",
    \    "set_breakpoint" : "<F10>",
    \    "get_context" : "<F11>",
    \    "eval_under_cursor" : "<F12>",
    \    "eval_visual" : "<Leader>e",
    \}
<

As you can see, these are the default keys. You can change the keys using the
multi-line notation as shown above, or by setting individual keys: >

    let g:vdebug_keymap['run'] = '<C-s>'
<
Any options that you don't set will use the default value.

==============================================================================
7. Setting debugger features                                  *VdebugFeatures*

The DBGP protocol allows you to set features for debugging, such as the max 
length of data that the debugger returns. You can set these features in the Vim
dictionary g:vdebug_features, and they will be sent to the debugger when you 
start a new debugging session.

For example: >
   let g:vdebug_features['max_depth'] = 2048
<

This will send the command to the debugger to set the "max_depth" feature to 
2048.

For a list of features supported by DBGP see 
http://xdebug.org/docs-dbgp.php#feature-names.

==============================================================================
8. Using an IDE Key                                             *VdebugIDEKey*

An IDE key is used to restrict debugger connections, kind of like a password:
only a connection that supplies the same key as the IDE uses (in this case
Vdebug) will be used, otherwise it's ignored. For instance, using Xdebug and
PHP with Netbeans requires you to use the IDE key "netbeans-xdebug".

You can tell Vdebug to use an IDE key with the option
"g:vdebug_options['ide_key']" (see |VdebugOptions-ide_key|). This is empty by
default, so all connections will be picked up, even if an IDE key has been set
on the debugger engine side of things. It's useful to leave the IDE key option
empty if you're having trouble getting a connection, as it's one less thing to 
have to worry about.

If you do set an IDE key and a connection comes in with a different IDE key, it
will be ignored (and there will be a message saying so).

However, I find it best to leave out the IDE key all the time, as I use VIM for 
all my debugging and don't have to juggle multiple connections at a time.

Setting an IDE key varies between debugger implementations. For example, Xdebug 
can be initiated from the browser with the GET variable
XDEBUG_SESSION_START=<ide-key>, where <ide-key> is the key for that session.
From the command line, the environment variable "XDEBUG_CONFIG" holds the IDE
key.

==============================================================================
9. Debugging a script on a remote server                        *VdebugRemote*

This is where things get really cool. You don't have to be on the same machine
as the running script to be able to debug it: you can tell the remote script to
use your machine's IP and debugger port, and you can pick up the remote
connection.

There are a couple of hurdles to overcome in doing this:
    
    1. File paths are unlikely to be the same on the local and remote machines
    2. You need to bind Vdebug to the right address, and make sure there's a
       network route between the two machines.

------------------------------------------------------------------------------
9.1 File path mapping                                  *VdebugRemoteFilePaths*

Firstly, file paths aren't a problem. You can use the options "remote_path" and
"local_path" to swap out sections of the file URIs to make them compatible with
each other.

Let's say we're debugging a file on a remote machine, and the path is
/home/user/scripts/myscript.php. On my machine the same script is located in
/home/jon/php/myscript.php. I would have to set the remote and local path
options as so: >

    let g:vdebug_options['path_maps'] = {"/home/user/scripts": "/home/jon/php"}
<
When the debugger engine sends any file paths, a straight swap of the paths is
done, so all instances of "/home/user/scripts" are replaced with
"/home/jon/php". The opposite is done when sending file paths in the other
direction.

It is possible to have multiple file path mappings by adding more items in the
"path_maps" dictionary.

------------------------------------------------------------------------------
9.2 Connecting the two machines                       *VdebugRemoteConnection*

This part depends a lot upon your network set-up and firewall rules. But here's
the basic information:

    * You need to bind Vdebug to an address that's visible to the remote
      machine (i.e. not "localhost")
    * You must have port 9000 allowed by any firewall you might have on your
      machine or router

I'll give an example of my own here. I had two machines on an internal network,
one was my desktop (192.168.1.1) and the other was a server (192.168.1.2) running 
the script that I wanted to debug on my desktop. I configured Xdebug on the 
server to use my desktop's IP address as the remote host. I then set the Vdebug
server address to be "192.168.1.1" (NOT "localhost") in the options: >

    let g:vdebug_options['server'] = "192.168.1.1"
<
I also had to set an Xdebug option "remote_connect_back=on" in the INI file on
the server. This combination of things allowed me to accept remote connections 
on my desktop.

The two machines don't have to be on an internal network, but if they aren't
then I can all but guarantee that you will have to route port 9000 to your 
machine using your router, as it will be blocked by default.

==============================================================================
10. Troubleshooting/FAQ                                *VdebugTroubleshooting*

If you have any questions or problems that aren't addressed or fixed here then
feel free to raise an issue on the Github page https://github.com/joonty/vdebug
or email me at <jon AT joncairns.com>. If the question is good I might even add
it to this list.

    Q. I can't get the debugger to run! Pressing <F5> does nothing.
    A. The most common reason for this is that your VIM installation is not
       compiled with Python support. To check this, run "vim --version" and check 
       for any mention of Python. If it is compiled with Python support, try
       remapping the start key to something else, e.g: >
        :let g:vdebug_keymap['run'] = '<C-s>'
<

    Q. I'm listening for connections with Vdebug, but when I run the script it
        doesn't do anything.
    A. This is either due to the debugger engine not being activated, or
        differing connection details. Check that the debugger is installed for
        the language you're using and that you're doing what's necessary to
        activate the engine when running the script (e.g. setting environment
        variables/URL variables). If the problem persists, check that the
        debugger engine is connecting the same port and address that Vdebug is
        binding to (the 'port' and 'server' options). Also check that the IDE
        key option is empty.

    Q. I can't debug a script on a remote machine, what's going on?
    A. Have you read the section on remote debugging, |VdebugRemote|? I mean,
        have you REALLY read it? If you have, then drop me an email with your
        problem and I'll try to help.

    Q. I don't seem to be able to get "call" or "return" breakpoints to work,
        any idea why?
    A. I've only ever been able to get these to work with global functions, not
        classes or objects. There is a very small amount of information on the
        Interwebs regarding this problem, and Xdebug says that it's been
        solved. However, no-one seems to know what syntax to use for class and
        object method names. First one to discover it wins a prize! (The prize
        of feeling good about helping others)

    Q. When setting a breakpoint I get the message that it isn't supported, why
        is that?
    A. Implementation of every feature is down to each debugger engine, and
        they pick and choose what goes in. Without modifying the engine's
        source there's nothing I can do I'm afraid :(

    Q. I can't switch variable context when debugging a Ruby script - I keep
        getting a long error. How can I fix it?
    A. This is addressed in |VdebugSetUpRuby|. A patch needs to be applied to
        the debugger engine code.

    Q. I can't use the eval commands when debugging a Python script - I keep
        getting an error about not providing length. How can I fix it?
    A. This is addressed in |VdebugSetUpPython|. A patch needs to be applied 
        to the debugger engine code.

    Q. I am debugging a PHP script and VDebug won't stop at my breakpoint, but 
        it will stop at other breakpoints. What do I do?
    A. You should try reproducing this case outside of your (likely large) 
        codebase. In the meantime, you can use the xdebug_break() function to 
        hardcode a breakpoint in your file.

    Q. I keep getting error <x> when doing <y>.
    A. Send the details of the error to me at the email address at the top of
        this section, or raise an issue on the Github page. Please supply the
        version of Vdebug, your Vim version and your OS to make it as easy as
        possible to diagnose!

    Q. Can you implement feature <x>?
    A. Maybe - raise an issue on the Github page (top of this section) and I'll
        weigh up the benefits vs time. Either that, or you can fork the
        repository and try to implement it yourself! I do accept merges.

    Q. Why doesn't Ross, the largest friend, simply eat the other ones?
    A. Think of the indigestion that would result.


==============================================================================
11. Acknowledgements                                  *VdebugAcknowledgements*

This plugin was inspired by the original Xdebug plugin created by Seung Woo Shin 
(<segv <at> sayclub.com>),
http://www.vim.org/scripts/script.php?script_id=1152. There are even a few
remnants of the original code, but not many. He showed us all that it was
possible.

Thanks to everyone who's contributed ideas and code so far, including Githubbers
teranex, qstrahl, artnez, csomme and beatle. Also thanks to Gareth Oslar to 
pointing out that Vdebug (almost) worked with NodeJS.