Add settings for the Alex linter

The executable for the Alex linter is currently hard-coded as 'alex',
which is an issue given the fact that it conflicts with the Haskell
lexer generator, whose executable is also called 'alex', has been around
a dozen years before the linter, and is packaged in the official
repositories of the major Linux distributions.

This commit adds options to use a local executable for the alex linter
(which is a node package), and an option to set a custom executable.

As side changes:
* The pattern in the alex handler is made more readable by turnig it
  into a very-magic regex.
* Alex handles plain text, markdown, and HTML. Specific flags for HTML
  and markdown are provided when instantiating the linters for the
  respective filetypes, while before those formats were treated as plain
  text.

18 files changed, 105 insertions, 108 deletions

diff --git a/ale_linters/asciidoc/alex.vim b/ale_linters/asciidoc/alex.vim
index 79b04fc3..97976b2c 100644
--- a/ale_linters/asciidoc/alex.vim
+++ b/ale_linters/asciidoc/alex.vim
@@ -1,11 +1,4 @@
 " Author: Johannes Wienke <languitar@semipol.de>
 " Description: alex for asciidoc files
 
-call ale#linter#Define('help', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('asciidoc', '--text')
diff --git a/ale_linters/help/alex.vim b/ale_linters/help/alex.vim
index 21b23b4f..9be00a82 100644
--- a/ale_linters/help/alex.vim
+++ b/ale_linters/help/alex.vim
@@ -1,11 +1,4 @@
 " Author: Johannes Wienke <languitar@semipol.de>
 " Description: alex for help files
 
-call ale#linter#Define('help', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('help', '--text')
diff --git a/ale_linters/html/alex.vim b/ale_linters/html/alex.vim
index 5a1f61e9..97756753 100644
--- a/ale_linters/html/alex.vim
+++ b/ale_linters/html/alex.vim
@@ -1,11 +1,4 @@
 " Author: Johannes Wienke <languitar@semipol.de>
 " Description: alex for HTML files
 
-call ale#linter#Define('html', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('html', '--html')
diff --git a/ale_linters/mail/alex.vim b/ale_linters/mail/alex.vim
index b0651ccd..0fceea7b 100644
--- a/ale_linters/mail/alex.vim
+++ b/ale_linters/mail/alex.vim
@@ -1,11 +1,4 @@
 " Author: Johannes Wienke <languitar@semipol.de>
-" Description: alex for HTML files
+" Description: alex for mail files
 
-call ale#linter#Define('mail', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('mail', '--text')
diff --git a/ale_linters/markdown/alex.vim b/ale_linters/markdown/alex.vim
index 29306141..63769b5e 100644
--- a/ale_linters/markdown/alex.vim
+++ b/ale_linters/markdown/alex.vim
@@ -1,11 +1,4 @@
 " Author: Johannes Wienke <languitar@semipol.de>
 " Description: alex for markdown files
 
-call ale#linter#Define('markdown', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('markdown', '')
diff --git a/ale_linters/nroff/alex.vim b/ale_linters/nroff/alex.vim
index a10db2dd..3f06af26 100644
--- a/ale_linters/nroff/alex.vim
+++ b/ale_linters/nroff/alex.vim
@@ -1,11 +1,4 @@
 " Author: Johannes Wienke <languitar@semipol.de>
 " Description: alex for nroff files
 
-call ale#linter#Define('nroff', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('nroff', '--text')
diff --git a/ale_linters/po/alex.vim b/ale_linters/po/alex.vim
index 411d835b..05c67f15 100644
--- a/ale_linters/po/alex.vim
+++ b/ale_linters/po/alex.vim
@@ -1,11 +1,4 @@
 " Author: Cian Butler https://github.com/butlerx
 " Description: alex for PO files
 
-call ale#linter#Define('po', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('po', '--text')
diff --git a/ale_linters/pod/alex.vim b/ale_linters/pod/alex.vim
index 5c09befb..c89f8330 100644
--- a/ale_linters/pod/alex.vim
+++ b/ale_linters/pod/alex.vim
@@ -1,11 +1,4 @@
 " Author: Johannes Wienke <languitar@semipol.de>
 " Description: alex for pod files
 
-call ale#linter#Define('pod', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('pod', '--text')
diff --git a/ale_linters/rst/alex.vim b/ale_linters/rst/alex.vim
index e637eae7..e7ca6fa0 100644
--- a/ale_linters/rst/alex.vim
+++ b/ale_linters/rst/alex.vim
@@ -1,11 +1,4 @@
 " Author: Johannes Wienke <languitar@semipol.de>
 " Description: alex for rst files
 
-call ale#linter#Define('rst', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('rst', '--text')
diff --git a/ale_linters/tex/alex.vim b/ale_linters/tex/alex.vim
index 78c530f7..5d9aec66 100644
--- a/ale_linters/tex/alex.vim
+++ b/ale_linters/tex/alex.vim
@@ -1,11 +1,4 @@
 " Author: Johannes Wienke <languitar@semipol.de>
 " Description: alex for TeX files
 
-call ale#linter#Define('tex', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('tex', '--text')
diff --git a/ale_linters/texinfo/alex.vim b/ale_linters/texinfo/alex.vim
index 4a884579..4d245524 100644
--- a/ale_linters/texinfo/alex.vim
+++ b/ale_linters/texinfo/alex.vim
@@ -1,11 +1,4 @@
 " Author: Johannes Wienke <languitar@semipol.de>
 " Description: alex for texinfo files
 
-call ale#linter#Define('texinfo', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('texinfo', '--text')
diff --git a/ale_linters/text/alex.vim b/ale_linters/text/alex.vim
index c696367b..d87ed915 100644
--- a/ale_linters/text/alex.vim
+++ b/ale_linters/text/alex.vim
@@ -1,11 +1,4 @@
 " Author: Johannes Wienke <languitar@semipol.de>
 " Description: alex for text files
 
-call ale#linter#Define('text', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('text', '--text')
diff --git a/ale_linters/xhtml/alex.vim b/ale_linters/xhtml/alex.vim
index 60a9a7c9..97f3b59a 100644
--- a/ale_linters/xhtml/alex.vim
+++ b/ale_linters/xhtml/alex.vim
@@ -1,11 +1,4 @@
 " Author: Johannes Wienke <languitar@semipol.de>
 " Description: alex for XHTML files
 
-call ale#linter#Define('xhtml', {
-\   'name': 'alex',
-\   'executable': 'alex',
-\   'command': 'alex %s -t',
-\   'output_stream': 'stderr',
-\   'callback': 'ale#handlers#alex#Handle',
-\   'lint_file': 1,
-\})
+call ale#handlers#alex#DefineLinter('xhtml', '--text')
diff --git a/autoload/ale/handlers/alex.vim b/autoload/ale/handlers/alex.vim
index 853d3137..9cb546ec 100644
--- a/autoload/ale/handlers/alex.vim
+++ b/autoload/ale/handlers/alex.vim
@@ -1,10 +1,23 @@
 " Author: Johannes Wienke <languitar@semipol.de>
 " Description: Error handling for errors in alex output format
 
+function! ale#handlers#alex#GetExecutable(buffer) abort
+    return ale#node#FindExecutable(a:buffer, 'alex', [
+    \   'node_modules/.bin/alex',
+    \   'node_modules/alex/cli.js',
+    \])
+endfunction
+
+function! ale#handlers#alex#CreateCommandCallback(flags) abort
+    return {b -> ale#node#Executable(b, ale#handlers#alex#GetExecutable(b))
+    \            . ' %s '
+    \            . a:flags}
+endfunction
+
 function! ale#handlers#alex#Handle(buffer, lines) abort
     " Example output:
     "       6:256-6:262  warning  Be careful with “killed”, it’s profane in some cases      killed           retext-profanities
-    let l:pattern = '^ *\(\d\+\):\(\d\+\)-\(\d\+\):\(\d\+\) \+warning \+\(.\{-\}\)  \+\(.\{-\}\)  \+\(.\{-\}\)$'
+    let l:pattern = '\v^ *(\d+):(\d+)-(\d+):(\d+) +warning +(.{-})  +(.{-})  +(.{-})$'
     let l:output = []
 
     for l:match in ale#util#GetMatches(a:lines, l:pattern)
@@ -20,3 +33,21 @@ function! ale#handlers#alex#Handle(buffer, lines) abort
 
     return l:output
 endfunction
+
+" Define a linter for a specific filetype. Accept flags to adapt to the filetype.
+"    no flags  treat input as markdown
+"    --html    treat input as HTML
+"    --text    treat input as plaintext
+function! ale#handlers#alex#DefineLinter(filetype, flags) abort
+    call ale#Set('alex_executable', 'alex')
+    call ale#Set('alex_use_global', get(g:, 'ale_use_global_executables', 0))
+
+    call ale#linter#Define(a:filetype, {
+    \   'name': 'alex',
+    \   'executable_callback': 'ale#handlers#alex#GetExecutable',
+    \   'command_callback': ale#handlers#alex#CreateCommandCallback(a:flags),
+    \   'output_stream': 'stderr',
+    \   'callback': 'ale#handlers#alex#Handle',
+    \   'lint_file': 1,
+    \})
+endfunction
diff --git a/doc/ale.txt b/doc/ale.txt
index 006928ef..0ca64af9 100644
--- a/doc/ale.txt
+++ b/doc/ale.txt
@@ -20,7 +20,8 @@ CONTENTS                                                         *ale-contents*
     5.6 Symbol Search.....................|ale-symbol-search|
   6. Global Options.......................|ale-options|
     6.1 Highlights........................|ale-highlights|
-    6.2 Options for write-good Linter.....|ale-write-good-options|
+    6.2 Options for alex Linter...........|ale-alex-options|
+    6.3 Options for write-good Linter.....|ale-write-good-options|
   7. Integration Documentation............|ale-integrations|
     ada...................................|ale-ada-options|
       gcc.................................|ale-ada-gcc|
@@ -2219,7 +2220,29 @@ ALEWarningSign                                                 *ALEWarningSign*
 
 
 -------------------------------------------------------------------------------
-6.2. Options for write-good                            *ale-write-good-options*
+6.2. Options for alex                                        *ale-alex-options*
+
+The options for the alex linter are global because it does not make sense to
+have them specified on a per-language basis.
+
+g:ale_alex_executable                                   *g:ale_alex_executable*
+                                                        *b:ale_alex_executable*
+  Type: |String|
+  Default: `'alex'`
+
+  See |ale-integrations-local-executables|
+
+
+g:ale_alex_use_global                                   *g:ale_alex_use_global*
+                                                        *b:ale_alex_use_global*
+  Type: |Number|
+  Default: `get(g:, 'ale_use_global_executables', 0)`
+
+  See |ale-integrations-local-executables|
+
+
+-------------------------------------------------------------------------------
+6.3. Options for write-good                            *ale-write-good-options*
 
 The options for the write-good linter are global because it does not make
 sense to have them specified on a per-language basis.
diff --git a/test/command_callback/alex-node-modules-2/node_modules/alex/cli.js b/test/command_callback/alex-node-modules-2/node_modules/alex/cli.js
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/command_callback/alex-node-modules-2/node_modules/alex/cli.js
diff --git a/test/command_callback/alex-node-modules/node_modules/.bin/alex b/test/command_callback/alex-node-modules/node_modules/.bin/alex
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/test/command_callback/alex-node-modules/node_modules/.bin/alex
diff --git a/test/command_callback/test_alex_command_callback.vader b/test/command_callback/test_alex_command_callback.vader
new file mode 100644
index 00000000..98769e0b
--- /dev/null
+++ b/test/command_callback/test_alex_command_callback.vader
@@ -0,0 +1,34 @@
+Before:
+  call ale#assert#SetUpLinterTest('tex', 'alex')
+  call ale#test#SetFilename('test_file.tex')
+
+After:
+  call ale#assert#TearDownLinterTest()
+
+Execute(The global executable should be used when the local one cannot be found):
+  AssertLinter 'alex',
+  \ ale#Escape('alex') . ' %s --text',
+
+Execute(Should use the node_modules/.bin executable, if available):
+  call ale#test#SetFilename('alex-node-modules/test_file.tex')
+
+  AssertLinter ale#path#Simplify(g:dir . '/alex-node-modules/node_modules/.bin/alex'),
+  \ ale#Escape(ale#path#Simplify(g:dir . '/alex-node-modules/node_modules/.bin/alex'))
+  \ . ' %s --text',
+
+Execute(Should use the node_modules/alex executable, if available):
+  call ale#test#SetFilename('alex-node-modules-2/test_file.tex')
+
+  AssertLinter ale#path#Simplify(g:dir . '/alex-node-modules-2/node_modules/alex/cli.js'),
+  \ (has('win32') ? 'node.exe ' : '')
+  \ . ale#Escape(ale#path#Simplify(g:dir . '/alex-node-modules-2/node_modules/alex/cli.js'))
+  \ . ' %s --text',
+
+Execute(Should let users configure a global executable and override local paths):
+  call ale#test#SetFilename('write-good-node-modules-2/test_file.tex')
+
+  let g:ale_alex_executable = '/path/to/custom/alex'
+  let g:ale_alex_use_global = 1
+
+  AssertLinter '/path/to/custom/alex',
+  \ ale#Escape('/path/to/custom/alex') . ' %s --text'