*ale-development.txt* For Vim version 8.0. *ale-development* ALE Development Documentation =============================================================================== CONTENTS *ale-development-contents* 1. Introduction.........................|ale-development-introduction| 2. Design Goals.........................|ale-design-goals| 3. Coding Standards.....................|ale-coding-standards| 4. Testing ALE..........................|ale-development-tests| =============================================================================== 1. Introduction *ale-development-introduction* This document contains helpful information for ALE developers, including design goals, information on how to run the tests, coding standards, and so on. You should read this document if you want to get involved with ALE development. =============================================================================== 2. Design Goals *ale-design-goals* This section lists design goals for ALE, in no particular order. They are as follows. ALE code should be almost 100% VimL. This makes the plugin as portable as possible. ALE should run without needing any other plugins to be installed, to make installation simple. ALE can integrate with other plugins for more advanced functionality, non-essential functionality, or improving on basic first party functionality. ALE should check files with as many tools as possible by default, except where they cause security issues or make excessive use of resources on modern machines. ALE should be free of breaking changes to the public API, which is comprised of documented functions and options, until a major version is planned. Breaking changes should be preceded by a deprecation phase complete with warnings. Changes required for security may be an exception. ALE supports Vim 8 and above, and NeoVim 0.2.0 or newer. These are the earliest versions of Vim and NeoVim which support |job|, |timer|, |closure|, and |lambda| features. All ALE code should be written so it is compatible with these versions of Vim, or with version checks so particular features can degrade or fail gracefully. Just about everything should be documented and covered with tests. By and large, people shouldn't pay for the functionality they don't use. Care should be taken when adding new features, so supporting new features doesn't degrade the general performance of anything ALE does. LSP support will become more important as time goes on. ALE should provide better support for LSP features as time goes on. When merging pull requests, you should respond with `Cheers! :beers:`, purely for comedy value. =============================================================================== 3. Coding Standards *ale-coding-standards* The following general coding standards should be adhered to for Vim code. * Check your Vim code with `Vint` and do everything it says. ALE will check your Vim code with Vint automatically. See: https://github.com/Kuniwak/vint Read ALE's `Dockerfile` to see which version of `Vint` it uses. * Try to write descriptive and concise names for variables and functions. Names shouldn't be too short or too long. Think about others reading your code later on. * Use `snake_case` names for variables and arguments, and `PascalCase` names for functions. Prefix every variable name with its scope. (`l:`, `g:`, etc.) * Try to keep lines no longer than 80 characters, but this isn't an absolute requirement. * Use 4 spaces for every level of indentation in Vim code. * Add a blank line before every `function`, `if`, `for`, `while`, or `return`, which doesn't start a new level of indentation. This makes the logic in your code easier to follow. * End every file with a trailing newline character, but not with extra blank lines. Remove trailing whitespace from the ends of lines. * Write the full names of commands instead of abbreviations. For example, write `function` instead of `func`, and `endif` instead of `end`. * Write functions with `!`, so files can be reloaded. Use the |abort| keyword for all functions, so functions exit on the first error. * Make sure to credit yourself in files you have authored with `Author:` and `Description:` comments. In addition to the above general guidelines for the style of your code, you should also follow some additional rules designed to prevent mistakes. Some of these are reported with ALE's `custom-linting-rules` script. See |ale-development-tests|. * Don't leave stray `:echo` lines in code. Use `execute 'echo' ...` if you must echo something. * For strings use |is#| instead of |==#|, `is?` instead of `==?`, `isnot#` instead of `!=#`, and `isnot?` instead of `!=?`. This is because `'x' ==# 0` returns 1, while `'x' is# 0` returns 0, so you will experience fewer issues when numbers are compared with strings. `is` and `isnot` also do not throw errors when other objects like List or Dictionaries are compared with strings. * Don't use the `getcwd()` function in the ALE codebase. Most of ALE's code runs from asynchronous callback functions, and these functions can execute from essentially random buffers. Therefore, the `getcwd()` output is useless. Use `expand('#' . a:buffer . ':p:h')` instead. Don't use `expand('%...')` for the same reason. * Don't use the `simplify()` function. It doesn't simplify paths enough. Use `ale#path#Simplify()` instead. * Don't use the `shellescape()` function. It doesn't escape arguments properly on Windows. Use `ale#Escape()` instead, which will avoid escaping where it isn't needed, and generally escape arguments better on Windows. Apply the following guidelines when writing Vader test files. * Use 2 spaces for Vader test files, instead of the 4 spaces for Vim files. * If you write `Before` and `After` blocks, you should typically write them at the top of the file, so they run for all tests. There may be some tests where it make sense to modify the `Before` and `After` code part of the way through the file. * If you modify any settings or global variables, reset them in `After` blocks. The Vader `Save` and `Restore` commands can be useful for this purpose. * If you load or define linters in tests, write `call ale#linter#Reset()` in an `After` block. * Just write `Execute` blocks for Vader tests, and don't bother writing `Then` blocks. `Then` blocks execute after `After` blocks in older versions, and that can be confusing. Apply the following rules when writing Bash scripts. * Run `shellcheck`, and do everything it says. See: https://github.com/koalaman/shellcheck * Try to write scripts so they will run on Linux, BSD, or Mac OSX. =============================================================================== 4. Testing ALE *ale-development-tests* ALE is tested with a suite of tests executed in Travis CI and AppVeyor. ALE runs tests with the following versions of Vim in the following environments. 1. Vim 8.0.0027 on Linux via Travis CI. 2. NeoVim 0.2.0 on Linux via Travis CI. 3. NeoVim 0.3.0 on Linux via Travis CI. 4. Vim 8 (stable builds) on Windows via AppVeyor. If you are developing ALE code on Linux, Mac OSX, or BSD, you can run ALEs tests by installing Docker and running the `run-tests` script. Follow the instructions on the Docker site for installing Docker. See: https://docs.docker.com/install/ NOTE: Don't forget to add your user to the `docker` group on Linux, or Docker just won't work. See: https://docs.docker.com/install/linux/linux-postinstall/ If you run simply `./run-tests` from the ALE repository root directory, the latest Docker image for tests will be downloaded if needed, and the script will run all of the tests in Vader, Vint checks, and several Bash scripts for finding extra issues. Run `./run-tests --help` to see all of the options the script supports. Note that the script supports selecting particular test files. Generally write tests for any changes you make. The following types of tests are recommended for the following types of code. * New/edited error handler callbacks -> Write tests in `test/handler` * New/edited command callbacks -> Write tests in `test/command_callback` * New/edited fixer functions -> Write tests in `test/fixers` Look at existing tests in the codebase for examples of how to write tests. Refer to the Vader documentation for general information on how to write Vader tests: https://github.com/junegunn/vader.vim When you add new linters or fixers, make sure to add them into the table in the README, and also into the |ale-support| list in the main help file. If you forget to keep them both in sync, you should see an error like the following in Travis CI. > ======================================== diff README.md and doc/ale.txt tables ======================================== Differences follow: --- /tmp/readme.qLjNhJdB 2018-07-01 16:29:55.590331972 +0100 +++ /tmp/doc.dAi8zfVE 2018-07-01 16:29:55.582331877 +0100 @@ -1 +1 @@ - ASM: gcc, foobar + ASM: gcc < Make sure to list documentation entries for linters and fixers in individual help files in the table of contents, and to align help tags to the right margin. For example, if you add a heading for an `aardvark` tool to `ale-python.txt` with a badly aligned doc tag, you will see errors like so. > ======================================== Look for badly aligned doc tags ======================================== Badly aligned tags follow: doc/ale-python.txt:aardvark ... ======================================== Look for table of contents issues ======================================== Check for bad ToC sorting: Check for mismatched ToC and headings: --- /tmp/table-of-contents.mwCFOgSI 2018-07-01 16:33:25.068811878 +0100 +++ /tmp/headings.L4WU0hsO 2018-07-01 16:33:25.076811973 +0100 @@ -168,6 +168,7 @@ pyrex (cython), ale-pyrex-options cython, ale-pyrex-cython python, ale-python-options + aardvark, ale-python-aardvark autopep8, ale-python-autopep8 black, ale-python-black flake8, ale-python-flake8 < Make sure to make the table of contents match the headings, and to keep the doc tags on the right margin. =============================================================================== vim:tw=78:ts=2:sts=2:sw=2:ft=help:norl: