Add parsers parameter to readConfig/Sync to support non-JSON formats like YAML (fixes #118).

README.md

@@ -400,9 +400,13 @@ uses rule aliases (ex: `no-hard-tabs`) instead of names (ex: `MD010`).
 
 ### Config
 
-The `options.config` configuration object is simple and can be loaded as JSON
-in many cases. To take advantage of shared configuration where one file `extends`
-another, the following functions are useful.
+The `options.config` configuration object is simple and can be stored in a file
+for readability and easy reuse. The `readConfig` and `readConfigSync` functions
+load configuration settings and support the `extends` keyword for referencing
+other files (see above).
+
+By default, configuration files are parsed as JSON (and named `.markdownlint.json`).
+Custom parsers can be provided to handle other formats like JSONC, YAML, and TOML.
 
 Asynchronous interface:
 
@@ -411,10 +415,11 @@ Asynchronous interface:
  * Read specified configuration file.
  *
  * @param {String} file Configuration file name/path.
+ * @param {Array} [parsers] Optional parsing function(s).
  * @param {Function} callback Callback (err, result) function.
  * @returns {void}
  */
-function readConfig(file, callback) { ... }
+function readConfig(file, parsers, callback) { ... }
 ```
 
 Synchronous interface:
@@ -424,16 +429,17 @@ Synchronous interface:
  * Read specified configuration file synchronously.
  *
  * @param {String} file Configuration file name/path.
+ * @param {Array} [parsers] Optional parsing function(s).
  * @returns {Object} Configuration object.
  */
-function readConfigSync(file) { ... }
+function readConfigSync(file, parsers) { ... }
 ```
 
 #### file
 
 Type: `String`
 
-Location of JSON configuration file to read.
+Location of configuration file to read.
 
 The `file` is resolved relative to the current working directory. If an `extends`
 key is present once read, its value will be resolved as a path relative to `file`
@@ -441,6 +447,22 @@ and loaded recursively. Settings from a file referenced by `extends` are applied
 first, then those of `file` are applied on top (overriding any of the same keys
 appearing in the referenced file).
 
+#### parsers
+
+Type: *Optional* `Array` of `Function` taking (`String`) and returning `Object`
+
+Array of functions to parse configuration files.
+
+The contents of a configuration file are passed to each parser function until one
+of them returns a value (vs. throwing an exception). Consequently, strict parsers
+should come before flexible parsers.
+
+For example:
+
+```js
+[ JSON.parse, require("toml").parse, require("js-yaml").safeLoad ]
+```
+
 #### callback
 
 Type: `Function` taking (`Error`, `Object`)

lib/markdownlint.js

@@ -422,6 +422,7 @@ function lintFile(
   }
 }
 
+// Lints files and strings
 function lintInput(options, synchronous, callback) {
   // Normalize inputs
   options = options || {};
@@ -517,34 +518,64 @@ function markdownlintSync(options) {
   return results;
 }
 
+// Parses the content of a configuration file
+function parseConfiguration(name, content, parsers) {
+  let config = null;
+  let message = "";
+  const errors = [];
+  // Try each parser
+  (parsers || [ JSON.parse ]).every((parser) => {
+    try {
+      config = parser(content);
+    } catch (ex) {
+      errors.push(ex.message);
+    }
+    return !config;
+  });
+  // Message if unable to parse
+  if (!config) {
+    errors.unshift(`Unable to parse '${name}'`);
+    message = errors.join("; ");
+  }
+  return {
+    config,
+    message
+  };
+}
+
 /**
  * Read specified configuration file.
  *
  * @param {String} file Configuration file name/path.
+ * @param {Array} [parsers] Optional parsing function(s).
  * @param {Function} callback Callback (err, result) function.
  * @returns {void}
  */
-function readConfig(file, callback) {
+function readConfig(file, parsers, callback) {
+  if (!callback) {
+    // @ts-ignore
+    callback = parsers;
+    parsers = null;
+  }
   // Read file
-  fs.readFile(file, shared.utf8Encoding, function handleFile(err, content) {
+  fs.readFile(file, shared.utf8Encoding, (err, content) => {
     if (err) {
       return callback(err);
     }
-    // Parse file
-    let config = null;
-    try {
-      config = JSON.parse(content);
-    } catch (ex) {
-      return callback(ex);
+    // Try to parse file
+    const { config, message } = parseConfiguration(file, content, parsers);
+    if (!config) {
+      return callback(new Error(message));
     }
-    if (config.extends) {
-      // Extend configuration
-      const extendsFile = path.resolve(path.dirname(file), config.extends);
-      readConfig(extendsFile, function handleConfig(errr, extendsConfig) {
+    // Extend configuration
+    const configExtends = config.extends;
+    if (configExtends) {
+      delete config.extends;
+      const extendsFile = path.resolve(path.dirname(file), configExtends);
+      readConfig(extendsFile, parsers, (errr, extendsConfig) => {
         if (errr) {
           return callback(errr);
         }
-        delete config.extends;
         callback(null, shared.assign(extendsConfig, config));
       });
     } else {
@@ -557,17 +588,24 @@ function readConfig(file, callback) {
  * Read specified configuration file synchronously.
  *
  * @param {String} file Configuration file name/path.
+ * @param {Array} [parsers] Optional parsing function(s).
  * @returns {Object} Configuration object.
  */
-function readConfigSync(file) {
-  // Parse file
-  let config = JSON.parse(fs.readFileSync(file, shared.utf8Encoding));
-  if (config.extends) {
-    // Extend configuration
-    config = shared.assign(
-      readConfigSync(path.resolve(path.dirname(file), config.extends)),
-      config);
+function readConfigSync(file, parsers) {
+  // Read file
+  const content = fs.readFileSync(file, shared.utf8Encoding);
+  // Try to parse file
+  const { config, message } = parseConfiguration(file, content, parsers);
+  if (!config) {
+    throw new Error(message);
+  }
+  // Extend configuration
+  const configExtends = config.extends;
+  if (configExtends) {
     delete config.extends;
+    return shared.assign(
+      readConfigSync(path.resolve(path.dirname(file), configExtends), parsers),
+      config);
   }
   return config;
 }

package.json

@@ -35,8 +35,10 @@
     "eslint": "~4.19.1",
     "glob": "~7.1.2",
     "istanbul": "~0.4.5",
+    "js-yaml": "~3.11.0",
     "nodeunit": "~0.11.2",
     "rimraf": "~2.6.2",
+    "toml": "~2.3.3",
     "tv4": "~1.3.0",
     "typescript": "~2.8.3",
     "uglify-js": "~3.3.25"

test/config/config-badcontent.txt

@@ -0,0 +1 @@
+@

test/config/config-child.yaml

@@ -0,0 +1,2 @@
+no-hard-tabs: false
+whitespace: false

test/config/config-grandparent-hybrid.yaml

@@ -0,0 +1,6 @@
+extends: config-parent-hybrid.toml
+MD003:
+  style: atx_closed
+MD007:
+  indent: 2
+no-hard-tabs: false

test/config/config-grandparent.yaml

@@ -0,0 +1,6 @@
+extends: config-parent.yaml
+MD003:
+  style: atx_closed
+MD007:
+  indent: 2
+no-hard-tabs: false

test/config/config-parent-hybrid.toml

@@ -0,0 +1,9 @@
+extends = "config-child.json"
+MD003 = false
+no-hard-tabs = true
+
+[MD007]
+indent = 4
+
+[line-length]
+line_length = 200

test/config/config-parent.yaml

@@ -0,0 +1,7 @@
+extends: config-child.yaml
+MD003: false
+MD007:
+  indent: 4
+no-hard-tabs: true
+line-length:
+  line_length: 200

test/markdownlint-test.js

@@ -924,6 +924,7 @@ module.exports.readmeHeadings = function readmeHeadings(test) {
           "#### result",
           "### Config",
           "#### file",
+          "#### parsers",
           "#### callback",
           "#### result",
           "## Usage",
@@ -1466,6 +1467,72 @@ module.exports.configBadChildJson = function configBadChildJson(test) {
     });
 };
 
+module.exports.configSingleYaml = function configSingleYaml(test) {
+  test.expect(2);
+  markdownlint.readConfig(
+    "./test/config/config-child.yaml",
+    [ require("js-yaml").safeLoad ],
+    function callback(err, actual) {
+      test.ifError(err);
+      const expected = require("./config/config-child.json");
+      test.deepEqual(actual, expected, "Config object not correct.");
+      test.done();
+    });
+};
+
+module.exports.configMultipleYaml = function configMultipleYaml(test) {
+  test.expect(2);
+  markdownlint.readConfig(
+    "./test/config/config-grandparent.yaml",
+    [ require("js-yaml").safeLoad ],
+    function callback(err, actual) {
+      test.ifError(err);
+      const expected = shared.assign(
+        shared.assign(
+          shared.assign({}, require("./config/config-child.json")),
+          require("./config/config-parent.json")),
+        require("./config/config-grandparent.json"));
+      delete expected.extends;
+      test.deepEqual(actual, expected, "Config object not correct.");
+      test.done();
+    });
+};
+
+module.exports.configMultipleHybrid = function configMultipleHybrid(test) {
+  test.expect(2);
+  markdownlint.readConfig(
+    "./test/config/config-grandparent-hybrid.yaml",
+    [ JSON.parse, require("toml").parse, require("js-yaml").safeLoad ],
+    function callback(err, actual) {
+      test.ifError(err);
+      const expected = shared.assign(
+        shared.assign(
+          shared.assign({}, require("./config/config-child.json")),
+          require("./config/config-parent.json")),
+        require("./config/config-grandparent.json"));
+      delete expected.extends;
+      test.deepEqual(actual, expected, "Config object not correct.");
+      test.done();
+    });
+};
+
+module.exports.configBadHybrid = function configBadHybrid(test) {
+  test.expect(4);
+  markdownlint.readConfig(
+    "./test/config/config-badcontent.txt",
+    [ JSON.parse, require("toml").parse, require("js-yaml").safeLoad ],
+    function callback(err, result) {
+      test.ok(err, "Did not get an error for bad child JSON.");
+      test.ok(err instanceof Error, "Error not instance of Error.");
+      test.ok(err.message.match(
+        // eslint-disable-next-line max-len
+        /^Unable to parse '[^']*'; Unexpected token \S+ in JSON at position \d+; Expected [^;]+ or end of input but "\S+" found.; end of the stream or a document separator is expected at line \d+, column \d+:[^;]*$/
+      ), "Error message unexpected.");
+      test.ok(!result, "Got result for bad child JSON.");
+      test.done();
+    });
+};
+
 module.exports.configSingleSync = function configSingleSync(test) {
   test.expect(1);
   const actual = markdownlint.readConfigSync("./test/config/config-child.json");
@@ -1530,8 +1597,10 @@ module.exports.configBadJsonSync = function configBadJsonSync(test) {
   }, function testError(err) {
     test.ok(err, "Did not get an error for bad JSON.");
     test.ok(err instanceof Error, "Error not instance of Error.");
-    test.ok(err.message.match(/Unexpected token b in JSON at position \d+/),
-      "Error message unexpected.");
+    test.ok(err.message.match(
+      // eslint-disable-next-line max-len
+      /^Unable to parse '[^']*'; Unexpected token \S+ in JSON at position \d+$/
+    ), "Error message unexpected.");
     return true;
   }, "Did not get exception for bad JSON.");
   test.done();
@@ -1544,13 +1613,72 @@ module.exports.configBadChildJsonSync = function configBadChildJsonSync(test) {
   }, function testError(err) {
     test.ok(err, "Did not get an error for bad child JSON.");
     test.ok(err instanceof Error, "Error not instance of Error.");
-    test.ok(err.message.match(/Unexpected token b in JSON at position \d+/),
-      "Error message unexpected.");
+    test.ok(err.message.match(
+      // eslint-disable-next-line max-len
+      /^Unable to parse '[^']*'; Unexpected token \S+ in JSON at position \d+$/
+    ), "Error message unexpected.");
     return true;
   }, "Did not get exception for bad child JSON.");
   test.done();
 };
 
+module.exports.configSingleYamlSync = function configSingleYamlSync(test) {
+  test.expect(1);
+  const actual = markdownlint.readConfigSync(
+    "./test/config/config-child.yaml", [ require("js-yaml").safeLoad ]);
+  const expected = require("./config/config-child.json");
+  test.deepEqual(actual, expected, "Config object not correct.");
+  test.done();
+};
+
+module.exports.configMultipleYamlSync = function configMultipleYamlSync(test) {
+  test.expect(1);
+  const actual = markdownlint.readConfigSync(
+    "./test/config/config-grandparent.yaml", [ require("js-yaml").safeLoad ]);
+  const expected = shared.assign(
+    shared.assign(
+      shared.assign({}, require("./config/config-child.json")),
+      require("./config/config-parent.json")),
+    require("./config/config-grandparent.json"));
+  delete expected.extends;
+  test.deepEqual(actual, expected, "Config object not correct.");
+  test.done();
+};
+
+module.exports.configMultipleHybridSync =
+function configMultipleHybridSync(test) {
+  test.expect(1);
+  const actual = markdownlint.readConfigSync(
+    "./test/config/config-grandparent-hybrid.yaml",
+    [ JSON.parse, require("toml").parse, require("js-yaml").safeLoad ]);
+  const expected = shared.assign(
+    shared.assign(
+      shared.assign({}, require("./config/config-child.json")),
+      require("./config/config-parent.json")),
+    require("./config/config-grandparent.json"));
+  delete expected.extends;
+  test.deepEqual(actual, expected, "Config object not correct.");
+  test.done();
+};
+
+module.exports.configBadHybridSync = function configBadHybridSync(test) {
+  test.expect(4);
+  test.throws(function badHybridCall() {
+    markdownlint.readConfigSync(
+      "./test/config/config-badcontent.txt",
+      [ JSON.parse, require("toml").parse, require("js-yaml").safeLoad ]);
+  }, function testError(err) {
+    test.ok(err, "Did not get an error for bad content.");
+    test.ok(err instanceof Error, "Error not instance of Error.");
+    test.ok(err.message.match(
+      // eslint-disable-next-line max-len
+      /^Unable to parse '[^']*'; Unexpected token \S+ in JSON at position \d+; Expected [^;]+ or end of input but "\S+" found.; end of the stream or a document separator is expected at line \d+, column \d+:[^;]*$/
+    ), "Error message unexpected.");
+    return true;
+  }, "Did not get exception for bad content.");
+  test.done();
+};
+
 module.exports.customRulesV0 = function customRulesV0(test) {
   test.expect(4);
   const customRulesMd = "./test/custom-rules.md";