Suppress warning about .eslintignore'd file (#836)

* Suppress warning about .eslintignore'd file

* Fix slightly ironic lint error

* Lock error suppression behind a variable; add docs and tests

autoload/ale/handlers/eslint.vim

@@ -4,6 +4,7 @@
 call ale#Set('javascript_eslint_options', '')
 call ale#Set('javascript_eslint_executable', 'eslint')
 call ale#Set('javascript_eslint_use_global', 0)
+call ale#Set('javascript_eslint_suppress_eslintignore', 0)
 
 function! ale#handlers#eslint#GetExecutable(buffer) abort
     return ale#node#FindExecutable(a:buffer, 'javascript_eslint', [
@@ -82,6 +83,12 @@ function! ale#handlers#eslint#Handle(buffer, lines) abort
         let l:type = 'Error'
         let l:text = l:match[3]
 
+        if ale#Var(a:buffer, 'javascript_eslint_suppress_eslintignore')
+            if l:text is# 'File ignored because of a matching ignore pattern. Use "--no-ignore" to override.'
+                continue
+            endif
+        endif
+
         " Take the error type from the output if available.
         if !empty(l:match[4])
             let l:type = split(l:match[4], '/')[0]

doc/ale-javascript.txt

@@ -50,6 +50,16 @@ g:ale_javascript_eslint_use_global         *g:ale_javascript_eslint_use_global*
   See |ale-integrations-local-executables|
 
 
+g:ale_javascript_eslint_suppress_eslintignore
+                                *g:ale_javascript_eslint_suppress_eslintignore*
+                                *b:ale_javascript_eslint_suppress_eslintignore*
+  Type: |Number|
+  Default: `0`
+
+  This variable can be set to disable the warning that linting is disabled on
+  the current file due to being covered by `.eslintignore`.
+
+
 ===============================================================================
 prettier                                              *ale-javascript-prettier*
 

test/eslint-test-files/eslintignore/ignored.js

@@ -0,0 +1 @@
+var foo = "bar";

test/test_eslint_suppress_eslintignore.vader

@@ -0,0 +1,38 @@
+Before:
+  Save g:ale_javascript_eslint_suppress_eslintignore
+
+  call ale#test#SetDirectory('/testplugin/test')
+
+  runtime ale_linters/javascript/eslint.vim
+
+After:
+  Restore
+
+  call ale#test#RestoreDirectory()
+  call ale#linter#Reset()
+
+Execute(eslint should warn about ignored file):
+  call ale#test#SetFilename('eslint-test-files/eslintignore/ignore.js')
+
+  AssertEqual
+  \ [{
+  \    'lnum': 0,
+  \    'col': 0,
+  \    'type': 'W',
+  \    'text': 'File ignored because of a matching ignore pattern. Use "--no-ignore" to override. [Warning]'
+  \ }],
+  \ ale#handlers#eslint#Handle(347, [
+  \  '/path/to/some/ignored.js:0:0: File ignored because of a matching ignore pattern. Use "--no-ignore" to override. [Warning]',
+  \ ])
+
+
+Execute(eslint should not warn about ignored file when configured):
+  let g:ale_javascript_eslint_suppress_eslintignore = 1
+
+  call ale#test#SetFilename('eslint-test-files/eslintignore/ignore.js')
+
+  AssertEqual
+  \ [],
+  \ ale#handlers#eslint#Handle(347, [
+  \  '/path/to/some/ignored.js:0:0: File ignored because of a matching ignore pattern. Use "--no-ignore" to override. [Warning]',
+  \ ])