Fix 2891 - eslint not showing errors.

ESLint errors are contained in an array that can contain different
stuff other than JSON error messages. This patch iterates over the whole
array ignoring any non-json data.

autoload/ale/handlers/eslint.vim

@@ -84,11 +84,14 @@ function! s:CheckForBadConfig(buffer, lines) abort
 endfunction
 
 function! s:parseJSON(buffer, lines) abort
-    try
-        let l:parsed = json_decode(a:lines[-1])
-    catch
-        return []
-    endtry
+    let l:parsed = []
+
+    for l:line in a:lines
+        try
+            let l:parsed = extend(l:parsed, json_decode(l:line))
+        catch
+        endtry
+    endfor
 
     if type(l:parsed) != v:t_list || empty(l:parsed)
         return []

test/handler/test_eslint_json_handler.vader

@@ -21,6 +21,7 @@ After:
   unlet! g:config_error_lines
 
 Execute(The eslint handler should parse json correctly):
+  call ale#test#SetFilename('foo.js')
   AssertEqual
   \ [
   \   {
@@ -53,6 +54,21 @@ Execute(The eslint handler should parse json correctly):
   \ '[{"filePath":"foo.js","messages":[{"ruleId":"no-unused-vars","severity":1,"message":"''variable'' is assigned a value but never used.","line":1,"column":7,"nodeType":"Identifier","endLine":1,"endColumn":15},{"ruleId":"semi","severity":1,"message":"Missing semicolon.","line":5,"column":15,"nodeType":"ExpressionStatement","fix":{"range":[46,46],"text":";"}},{"ruleId":"no-redeclare","severity":2,"message":"''variable'' is already defined.","line":7,"column":7,"nodeType":"Identifier","endLine":7,"endColumn":15}],"errorCount":1,"warningCount":3,"fixableErrorCount":0,"fixableWarningCount":1,"source":"const variable = {\n    a: 3\n};\n\nconsole.log(1)\n\nclass variable {\n}\n"}]'
   \ ])
 
+Execute(The eslint handler should suppress deprecation warnings):
+  call ale#test#SetFilename('foo.js')
+  AssertEqual
+  \ [
+  \   {
+  \     'lnum': 1,
+  \     'col': 9,
+  \     'text': 'Parsing error: Unexpected token Controller',
+  \     'type': 'E',
+  \   }
+  \ ],
+  \ ale#handlers#eslint#HandleJSON(bufnr(''), [
+  \ '[{"filePath":"foo.js","messages":[{"ruleId":null,"fatal":true,"severity":2 ,"message":"Parsing error: Unexpected token Controller","line":1,"column":9}],"errorCount":1,"warningCount":0,"fixableErrorCount":0,"fixableWarningCount": 0,"source":"i:mport Controller from \"@ember/controller\";\nimport listViewControllerMixin from \"elearning/mixins/list-view-controller\";\nimport { inject as service } from \"@ember/service\";\n\nexport default Controller.extend(listViewControllerMixin(), {\n  modelName: \"notification\",\n  intl: service(),\n\n  flatpickrLocale: computed(\"intl.locale\", function() {\n    return this.intl.locale.firstObject.split(\"-\")[0];\n  })\n});\n"}]', '(node:616989) [ESLINT_LEGACY_OBJECT_REST_SPREAD] DeprecationWarning: The ''parserOptions.ecmaFeatures.experimentalObjectRestSpread'' option is deprecated. Use ''parser Options.ecmaVersion'' instead. (found in "node_modules/eslint-plugin-ember/lib/config/base.js")]'
+  \ ])
+
 Execute(The eslint handler should print a message about a missing configuration file):
   let g:config_error_lines = [
   \   '',
@@ -262,7 +278,7 @@ Execute(Suppressing missing configs shouldn't suppress module import errors):
   \ ale#handlers#eslint#HandleJSON(bufnr(''), g:config_error_lines[:])
 
 Execute(The eslint handler should hint about using typescript-eslint-parser):
-  silent! noautocmd file foo.ts
+  call ale#test#SetFilename('foo.ts')
 
   AssertEqual
   \ [
@@ -326,7 +342,7 @@ Execute(Failing to connect to eslint_d should be handled correctly):
   \ ])
 
 Execute(Disabling warnings about trailing spaces should work):
-  silent! noautocmd file foo.ts
+  call ale#test#SetFilename('foo.js')
 
   AssertEqual
   \ [