Update MD040/fenced-code-language to add allowed_languages parameter (fixes #610).

demo/markdownlint-browser.js

@@ -4152,16 +4152,25 @@ module.exports = {
 "use strict";
 // @ts-check
 
-const { addErrorContext, filterTokens } = __webpack_require__(/*! ../helpers */ "../helpers/helpers.js");
+const { addError, addErrorContext, filterTokens } = __webpack_require__(/*! ../helpers */ "../helpers/helpers.js");
 module.exports = {
     "names": ["MD040", "fenced-code-language"],
     "description": "Fenced code blocks should have a language specified",
     "tags": ["code", "language"],
     "function": function MD040(params, onError) {
+        let allowed = params.config.allowed_languages;
+        allowed = Array.isArray(allowed) ?
+            allowed.map((lang) => lang.toLowerCase()) :
+            [];
         filterTokens(params, "fence", function forToken(token) {
-            if (!token.info.trim()) {
+            const lang = token.info.trim();
+            if (lang === "") {
                 addErrorContext(onError, token.lineNumber, token.line);
             }
+            else if (allowed.length > 0 &&
+                !allowed.includes(lang.toLowerCase())) {
+                addError(onError, token.lineNumber, `"${lang}" is not allowed`);
+            }
         });
     }
 };

doc/Rules.md

@@ -1571,6 +1571,8 @@ Tags: code, language
 
 Aliases: fenced-code-language
 
+Parameters: allowed_languages (array of string; default [])
+
 This rule is triggered when fenced code blocks are used, but a language isn't
 specified:
 
@@ -1598,6 +1600,9 @@ Plain text in a code block
 ```
 ````
 
+You can configure the `allowed_languages` parameter to specify a list of
+languages code blocks could use. The default value is `[]` which means any language specifier is valid.
+
 Rationale: Specifying a language improves content rendering by using the
 correct syntax highlighting for code. More information:
 <https://cirosantilli.com/markdown-style-guide#option-code-fenced>.

lib/md040.js

@@ -2,16 +2,30 @@
 
 "use strict";
 
-const { addErrorContext, filterTokens } = require("../helpers");
+const { addError, addErrorContext, filterTokens } = require("../helpers");
 
 module.exports = {
   "names": [ "MD040", "fenced-code-language" ],
   "description": "Fenced code blocks should have a language specified",
   "tags": [ "code", "language" ],
   "function": function MD040(params, onError) {
+    let allowed = params.config.allowed_languages;
+    allowed = Array.isArray(allowed) ?
+      allowed.map((lang) => lang.toLowerCase()) :
+      [];
     filterTokens(params, "fence", function forToken(token) {
-      if (!token.info.trim()) {
+      const lang = token.info.trim();
+      if (lang === "") {
         addErrorContext(onError, token.lineNumber, token.line);
+      } else if (
+        allowed.length > 0 &&
+        !allowed.includes(lang.toLowerCase())
+      ) {
+        addError(
+          onError,
+          token.lineNumber,
+          `"${lang}" is not allowed`
+        );
       }
     });
   }

schema/.markdownlint.jsonc

@@ -207,7 +207,10 @@
   "MD039": true,
 
   // MD040/fenced-code-language - Fenced code blocks should have a language specified
-  "MD040": true,
+  "MD040": {
+    // List of languages
+    "allowed_languages": []
+  },
 
   // MD041/first-line-heading/first-line-h1 - First line in a file should be a top-level heading
   "MD041": {

schema/.markdownlint.yaml

@@ -188,7 +188,9 @@ MD038: true
 MD039: true
 
 # MD040/fenced-code-language - Fenced code blocks should have a language specified
-MD040: true
+MD040:
+  # List of languages
+  allowed_languages: []
 
 # MD041/first-line-heading/first-line-h1 - First line in a file should be a top-level heading
 MD041:

schema/build-config-schema.js

@@ -347,6 +347,18 @@ for (const rule of rules) {
         }
       };
       break;
+    case "MD040":
+      scheme.properties = {
+        "allowed_languages": {
+          "description": "List of languages",
+          "type": "array",
+          "items": {
+            "type": "string"
+          },
+          "default": []
+        }
+      };
+      break;
     case "MD025":
     case "MD041":
       scheme.properties = {

schema/markdownlint-config-schema.json

@@ -669,8 +669,22 @@
     },
     "MD040": {
       "description": "MD040/fenced-code-language - Fenced code blocks should have a language specified",
-      "type": "boolean",
-      "default": true
+      "type": [
+        "boolean",
+        "object"
+      ],
+      "default": true,
+      "properties": {
+        "allowed_languages": {
+          "description": "List of languages",
+          "type": "array",
+          "items": {
+            "type": "string"
+          },
+          "default": []
+        }
+      },
+      "additionalProperties": false
     },
     "fenced-code-language": {
       "$ref": "#/properties/MD040"

test/markdownlint-test.js

@@ -925,7 +925,7 @@ test("readme", (t) => new Promise((resolve) => {
 }));
 
 test("rules", (t) => new Promise((resolve) => {
-  t.plan(374);
+  t.plan(375);
   fs.readFile("doc/Rules.md", "utf8",
     (err, contents) => {
       t.falsy(err);

test/md040-allowed_languages.json

@@ -0,0 +1,5 @@
+{
+  "MD040": {
+    "allowed_languages": ["js", "scss", "md", "TS"]
+  }
+}

test/md040-allowed_languages.md

@@ -0,0 +1,45 @@
+# md040-allowed_languages.md
+
+Code block with `html` not in allowed_languages:
+
+```html
+<h1>markdownlint</h1> {MD040:5}
+```
+
+Code block with `css` not in allowed_languages:
+
+```css
+body {}  {MD040:11}
+```
+
+Code block with `js` in allowed_languages:
+
+```js
+console.log('markdownlint')
+```
+
+Code block with `scss` in allowed_languages:
+
+```scss
+body {
+  h1 {
+    color: red;
+  }
+}
+```
+
+Code block with `md` in allowed_languages:
+
+```MD
+hello md
+```
+
+Code block with `TS` in allowed_languages:
+
+```ts
+body {
+  h1 {
+    color: red;
+  }
+}
+```

test/snapshots/markdownlint-test-scenarios.js.md

@@ -29318,6 +29318,87 @@ Generated by [AVA](https://avajs.dev).
       `,
     }
 
+## md040-allowed_languages.md
+
+> Snapshot 1
+
+    {
+      errors: [
+        {
+          errorContext: null,
+          errorDetail: '"html" is not allowed',
+          errorRange: null,
+          fixInfo: null,
+          lineNumber: 5,
+          ruleDescription: 'Fenced code blocks should have a language specified',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/Rules.md#md040',
+          ruleNames: [
+            'MD040',
+            'fenced-code-language',
+          ],
+        },
+        {
+          errorContext: null,
+          errorDetail: '"css" is not allowed',
+          errorRange: null,
+          fixInfo: null,
+          lineNumber: 11,
+          ruleDescription: 'Fenced code blocks should have a language specified',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/Rules.md#md040',
+          ruleNames: [
+            'MD040',
+            'fenced-code-language',
+          ],
+        },
+      ],
+      fixed: `# md040-allowed_languages.md␊
+      ␊
+      Code block with \`html\` not in allowed_languages:␊
+      ␊
+      \`\`\`html␊
+      <h1>markdownlint</h1> {MD040:5}␊
+      \`\`\`␊
+      ␊
+      Code block with \`css\` not in allowed_languages:␊
+      ␊
+      \`\`\`css␊
+      body {}  {MD040:11}␊
+      \`\`\`␊
+      ␊
+      Code block with \`js\` in allowed_languages:␊
+      ␊
+      \`\`\`js␊
+      console.log('markdownlint')␊
+      \`\`\`␊
+      ␊
+      Code block with \`scss\` in allowed_languages:␊
+      ␊
+      \`\`\`scss␊
+      body {␊
+        h1 {␊
+          color: red;␊
+        }␊
+      }␊
+      \`\`\`␊
+      ␊
+      Code block with \`md\` in allowed_languages:␊
+      ␊
+      \`\`\`MD␊
+      hello md␊
+      \`\`\`␊
+      ␊
+      Code block with \`TS\` in allowed_languages:␊
+      ␊
+      \`\`\`ts␊
+      body {␊
+        h1 {␊
+          color: red;␊
+        }␊
+      }␊
+      \`\`\`␊
+      `,
+    }
+
 ## md041-ignore-leading-comments-combined.md
 
 > Snapshot 1