feat: markdownlint rule to disallow opening angle brackets (#50)

configs/markdownlint.json

@@ -23,5 +23,6 @@
     "br_spaces": 0
   },
   "single-h1": false,
-  "no-inline-html": false
+  "no-inline-html": false,
+  "no-angle-brackets": false
 }

markdownlint-rules/emd002.js

@@ -0,0 +1,25 @@
+const { addError, filterTokens } = require('markdownlint/helpers');
+
+module.exports = {
+  names: ['EMD002', 'no-angle-brackets'],
+  description: 'No unescaped opening angle brackets in text (does not play nice with MDX)',
+  tags: ['brackets'],
+  function: function EMD002(params, onError) {
+    filterTokens(params, 'inline', (token) => {
+      for (const childToken of token.children) {
+        // childToken.line has the raw content, but may also contain
+        // more content than just childToken.content. This may cause
+        // the same line to produce multiple errors, unfortunately.
+        if (
+          childToken.type === 'text' &&
+          childToken.markup !== '<' &&
+          childToken.markup !== '<' &&
+          childToken.content.includes('<') &&
+          childToken.line.match(/(?<!\\)</g) !== null
+        ) {
+          addError(onError, token.lineNumber, 'Unescaped opening angle bracket');
+        }
+      }
+    });
+  },
+};

tests/__snapshots__/electron-markdownlint.spec.ts.snap

@@ -0,0 +1,6 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`electron-markdownlint should not allow opening angle brackets if EMD002 enabled 1`] = `
+"<root>angle-brackets.md:114 EMD002/no-angle-brackets No unescaped opening angle brackets in text (does not play nice with MDX) [Unescaped opening angle bracket]
+"
+`;

tests/electron-lint-markdown-links.spec.ts

@@ -30,7 +30,7 @@ describe('electron-lint-markdown-links', () => {
       '--root',
       FIXTURES_DIR,
       '--ignore',
-      '**/{broken,valid}-*-link.md',
+      '**/{{broken,valid}-*-link.md,*angle-brackets.md}',
       '*.md',
     );
 
@@ -45,6 +45,8 @@ describe('electron-lint-markdown-links', () => {
       '**/broken-{external,internal}-link.md',
       '--ignore',
       '**/{broken,valid}-cross-file-link.md',
+      '--ignore',
+      '**/*angle-brackets.md',
       '*.md',
     );
 

tests/electron-markdownlint.spec.ts

@@ -11,10 +11,10 @@ describe('electron-markdownlint', () => {
         path.resolve(__dirname, '../dist/bin/markdownlint-cli-wrapper.js'),
         path.resolve(FIXTURES_DIR, 'shortcut-links.md'),
       ],
-      { stdio: 'pipe' },
+      { stdio: 'pipe', encoding: 'utf-8' },
     );
 
-    expect(stderr.toString('utf-8')).toContain('EMD001/no-shortcut-reference-links');
+    expect(stderr).toContain('EMD001/no-shortcut-reference-links');
     expect(status).toEqual(1);
   });
 
@@ -30,4 +30,40 @@ describe('electron-markdownlint', () => {
 
     expect(status).toEqual(0);
   });
+
+  it('should not allow opening angle brackets if EMD002 enabled', () => {
+    const { status, stderr, stdout } = cp.spawnSync(
+      process.execPath,
+      [
+        path.resolve(__dirname, '../dist/bin/markdownlint-cli-wrapper.js'),
+        '--enable',
+        'EMD002',
+        '--',
+        path.resolve(FIXTURES_DIR, 'angle-brackets.md'),
+      ],
+      { stdio: 'pipe', encoding: 'utf-8' },
+    );
+
+    expect(stderr.replace(`${FIXTURES_DIR}${path.sep}`, '<root>')).toMatchSnapshot();
+    expect(stdout).toBe('');
+    expect(status).toEqual(1);
+  });
+
+  it('should allow escaped opening angle brackets if EMD002 enabled', () => {
+    const { status, stderr, stdout } = cp.spawnSync(
+      process.execPath,
+      [
+        path.resolve(__dirname, '../dist/bin/markdownlint-cli-wrapper.js'),
+        '--enable',
+        'EMD002',
+        '--',
+        path.resolve(FIXTURES_DIR, 'escaped-angle-brackets.md'),
+      ],
+      { stdio: 'pipe', encoding: 'utf-8' },
+    );
+
+    expect(stderr).toBe('');
+    expect(stdout).toBe('');
+    expect(status).toEqual(0);
+  });
 });