Allow user configuration files to be YAML-formatted.

README.md

@@ -23,7 +23,7 @@ $ markdownlint --help
     -V, --version                       output the version number
     -s, --stdin                         read from STDIN (no files)
     -o, --output [outputFile]           write issues to file (no console)
-    -c, --config [configFile]           configuration file
+    -c, --config [configFile]           configuration file (JSON or YAML)
     -i, --ignore [file|directory|glob]  files to ignore/exclude
 ```
 
@@ -47,7 +47,7 @@ The example of configuration file:
 
 See [test configuration file][test-config] or [style folder][style-folder] for more examples.
 
-CLI argument `--config` is not mandatory. If it is not provided, `markdownlint-cli` looks for file `.markdownlint.json` in current folder, or for file `.markdownlintrc` in current or all upper folders. The algorithm is described in details on [rc package page][rc-standards].
+CLI argument `--config` is not mandatory. If it is not provided, `markdownlint-cli` looks for file `.markdownlint.json` in current folder, or for file `.markdownlintrc` in current or all upper folders. The algorithm is described in details on [rc package page][rc-standards]. If `--config` argument is provided, the file must be valid JSON or YAML.
 
 ## Related
 

markdownlint.js

@@ -6,6 +6,7 @@ var fs = require('fs');
 var path = require('path');
 var program = require('commander');
 var getStdin = require('get-stdin');
+var jsYaml = require('js-yaml');
 var differenceWith = require('lodash.differencewith');
 var flatten = require('lodash.flatten');
 var extend = require('deep-extend');
@@ -31,7 +32,7 @@ function readConfiguration(args) {
   // from .markdownlint.json.
   if (userConfigFile) {
     try {
-      var userConfig = markdownlint.readConfigSync(userConfigFile);
+      var userConfig = markdownlint.readConfigSync(userConfigFile, [JSON.parse, jsYaml.safeLoad]);
       config = extend(config, userConfig);
     } catch (err) {
       console.warn('Cannot read or parse config file', args.config);
@@ -115,7 +116,7 @@ program
   .usage('[options] <files|directories|globs>')
   .option('-s, --stdin', 'read from STDIN (no files)')
   .option('-o, --output [outputFile]', 'write issues to file (no console)')
-  .option('-c, --config [configFile]', 'configuration file')
+  .option('-c, --config [configFile]', 'configuration file (JSON or YAML)')
   .option('-i, --ignore [file|directory|glob]', 'files to ignore/exclude', concatArray, []);
 
 program.parse(process.argv);

package.json

@@ -40,6 +40,7 @@
     "deep-extend": "~0.5.1",
     "get-stdin": "~5.0.1",
     "glob": "~7.0.3",
+    "js-yaml": "~3.11.0",
     "lodash.differencewith": "~4.5.0",
     "lodash.flatten": "~4.4.0",
     "markdownlint": "~0.10.0",

test/md043-config.yaml

@@ -0,0 +1,5 @@
+MD043:
+  headers:
+    - "# First"
+    - "## Second"
+    - "### Third"

test/test.js

@@ -320,3 +320,10 @@ test('--output with invalid path fails', async t => {
     t.throws(() => fs.accessSync(output, 'utf8'), Error);
   }
 });
+
+test('configuration file can be YAML', async t => {
+  const result = await execa('../markdownlint.js',
+    ['--config', 'md043-config.yaml', 'md043-config.md']);
+  t.true(result.stdout === '');
+  t.true(result.stderr === '');
+});