Update MD051/link-fragments to support GitHub-style line/column range syntax in URLs (refs #1117).

demo/markdownlint-browser.js

@@ -5470,7 +5470,9 @@ module.exports = {
             startColumn
           } = definition;
           const text = unescapeStringTokenText(definition);
-          if (text.length > 1 && text.startsWith("#") && !fragments.has(text) && !fragments.has(`#${encodeURIComponent(text.slice(1))}`)) {
+          const encodedText = `#${encodeURIComponent(text.slice(1))}`;
+          const lineFragmentRe = /^#L\d+(?:C\d+)?(?:-L\d+(?:C\d+)?)?$/;
+          if (text.length > 1 && text.startsWith("#") && !fragments.has(encodedText) && !lineFragmentRe.test(encodedText)) {
             // eslint-disable-next-line no-undef-init
             let context = undefined;
             // eslint-disable-next-line no-undef-init

doc-build/md051.md

@@ -16,6 +16,16 @@ generated name (see below):
 [Link](#heading-name)
 ```
 
+Furthermore, this rule mandates the use of lowercase for link fragments.
+Thus, even though the link points to the correct fragment, the following example
+will still trigger this rule:
+
+```markdown
+# Heading Name
+
+[Link](#Heading-Name)
+```
+
 Alternatively, some platforms allow the syntax `{#named-anchor}` to be used
 within a heading to provide a specific name (consisting of only lower-case
 letters, numbers, `-`, and `_`):
@@ -38,6 +48,28 @@ attribute can be used to define a fragment:
 An `a` tag can be useful in scenarios where a heading is not appropriate or for
 control over the text of the fragment identifier.
 
+GitHub supports links to [specific lines][github-lines-links].
+
+For example, to link to line 12 of current Markdown file:
+
+```markdown
+[Go to line 12](#L12)
+```
+
+GitHub also allows to specify a column number:
+
+```markdown
+[Go to line 12, column 34](#L12-L34)
+```
+
+Or a range of lines/columns:
+
+```markdown
+[Go to lines 12-34](#L12-L34)
+```
+
+So this rule will not report violations when this syntax is used.
+
 Rationale: [GitHub section links][github-section-links] are created
 automatically for every heading when Markdown content is displayed on GitHub.
 This makes it easy to link directly to different sections within a document.
@@ -51,3 +83,4 @@ append an incrementing integer as needed for uniqueness.
 
 [github-section-links]: https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#section-links
 [github-heading-algorithm]: https://github.com/gjtorikian/html-pipeline/blob/f13a1534cb650ba17af400d1acd3a22c28004c09/lib/html/pipeline/toc_filter.rb
+[github-lines-links]: https://docs.github.com/en/get-started/writing-on-github/working-with-advanced-formatting/creating-a-permanent-link-to-a-code-snippet#linking-to-markdown#linking-to-markdown

doc/Rules.md

@@ -2100,6 +2100,16 @@ generated name (see below):
 [Link](#heading-name)
 ```
 
+Furthermore, this rule mandates the use of lowercase for link fragments.
+Thus, even though the link points to the correct fragment, the following example
+will still trigger this rule:
+
+```markdown
+# Heading Name
+
+[Link](#Heading-Name)
+```
+
 Alternatively, some platforms allow the syntax `{#named-anchor}` to be used
 within a heading to provide a specific name (consisting of only lower-case
 letters, numbers, `-`, and `_`):
@@ -2122,6 +2132,28 @@ attribute can be used to define a fragment:
 An `a` tag can be useful in scenarios where a heading is not appropriate or for
 control over the text of the fragment identifier.
 
+GitHub supports links to [specific lines][github-lines-links].
+
+For example, to link to line 12 of current Markdown file:
+
+```markdown
+[Go to line 12](#L12)
+```
+
+GitHub also allows to specify a column number:
+
+```markdown
+[Go to line 12, column 34](#L12-L34)
+```
+
+Or a range of lines/columns:
+
+```markdown
+[Go to lines 12-34](#L12-L34)
+```
+
+So this rule will not report violations when this syntax is used.
+
 Rationale: [GitHub section links][github-section-links] are created
 automatically for every heading when Markdown content is displayed on GitHub.
 This makes it easy to link directly to different sections within a document.
@@ -2135,6 +2167,7 @@ append an incrementing integer as needed for uniqueness.
 
 [github-section-links]: https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#section-links
 [github-heading-algorithm]: https://github.com/gjtorikian/html-pipeline/blob/f13a1534cb650ba17af400d1acd3a22c28004c09/lib/html/pipeline/toc_filter.rb
+[github-lines-links]: https://docs.github.com/en/get-started/writing-on-github/working-with-advanced-formatting/creating-a-permanent-link-to-a-code-snippet#linking-to-markdown#linking-to-markdown
 
 <a name="md052"></a>
 

doc/md051.md

@@ -24,6 +24,16 @@ generated name (see below):
 [Link](#heading-name)
 ```
 
+Furthermore, this rule mandates the use of lowercase for link fragments.
+Thus, even though the link points to the correct fragment, the following example
+will still trigger this rule:
+
+```markdown
+# Heading Name
+
+[Link](#Heading-Name)
+```
+
 Alternatively, some platforms allow the syntax `{#named-anchor}` to be used
 within a heading to provide a specific name (consisting of only lower-case
 letters, numbers, `-`, and `_`):
@@ -46,6 +56,28 @@ attribute can be used to define a fragment:
 An `a` tag can be useful in scenarios where a heading is not appropriate or for
 control over the text of the fragment identifier.
 
+GitHub supports links to [specific lines][github-lines-links].
+
+For example, to link to line 12 of current Markdown file:
+
+```markdown
+[Go to line 12](#L12)
+```
+
+GitHub also allows to specify a column number:
+
+```markdown
+[Go to line 12, column 34](#L12-L34)
+```
+
+Or a range of lines/columns:
+
+```markdown
+[Go to lines 12-34](#L12-L34)
+```
+
+So this rule will not report violations when this syntax is used.
+
 Rationale: [GitHub section links][github-section-links] are created
 automatically for every heading when Markdown content is displayed on GitHub.
 This makes it easy to link directly to different sections within a document.
@@ -59,3 +91,4 @@ append an incrementing integer as needed for uniqueness.
 
 [github-section-links]: https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#section-links
 [github-heading-algorithm]: https://github.com/gjtorikian/html-pipeline/blob/f13a1534cb650ba17af400d1acd3a22c28004c09/lib/html/pipeline/toc_filter.rb
+[github-lines-links]: https://docs.github.com/en/get-started/writing-on-github/working-with-advanced-formatting/creating-a-permanent-link-to-a-code-snippet#linking-to-markdown#linking-to-markdown

lib/md051.js

@@ -119,11 +119,13 @@ module.exports = {
         for (const definition of definitions) {
           const { endColumn, startColumn } = definition;
           const text = unescapeStringTokenText(definition);
+          const encodedText = `#${encodeURIComponent(text.slice(1))}`;
+          const lineFragmentRe = /^#L\d+(?:C\d+)?(?:-L\d+(?:C\d+)?)?$/;
           if (
             (text.length > 1) &&
             text.startsWith("#") &&
-            !fragments.has(text) &&
+            !fragments.has(encodedText) &&
-            !fragments.has(`#${encodeURIComponent(text.slice(1))}`)
+            !lineFragmentRe.test(encodedText)
           ) {
             // eslint-disable-next-line no-undef-init
             let context = undefined;

test/link-fragments.md

@@ -86,6 +86,22 @@
 
 [Valid][escapedref]
 
+[Valid](#L7)
+
+[Valid](#L123)
+
+[Valid](#L30C11-L31C9)
+
+[Valid](#L30C11)
+
+[Valid](#L30C11-L31)
+
+[Valid](#L30C11-L31)
+
+[Valid](#L30-L31)
+
+[Valid](#l12-abc)
+
 ### Valid H3 Heading
 
 Text
@@ -171,6 +187,8 @@ Text
 
 ### Valid Heading\-With\_Embedded\_Escaping
 
+### L12 ABC
+
 <a name="namedlink"></a>
 
 <a id = idlink></a>
@@ -280,6 +298,22 @@ Valid Setext Heading with Named Fragment {#setext}
 
 [Invalid](#uppercase) {MD051}
 
+[Invalid](#l7) {MD051}
+
+[Invalid](#L12-abc) {MD051}
+
+[Invalid](#L7abc) {MD051}
+
+[Invalid](#L) {MD051}
+
+[Invalid](#L30C) {MD051}
+
+[Invalid](#L30L12) {MD051}
+
+[Invalid](#L30C11-) {MD051}
+
+[Invalid](#L30C11-L31C) {MD051}
+
 <!-- markdownlint-configure-file {
   "emphasis-style": false,
   "heading-style": false,

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

@@ -23678,7 +23678,7 @@ Generated by [AVA](https://avajs.dev).
             37,
           ],
           fixInfo: null,
-          lineNumber: 196,
+          lineNumber: 214,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23694,7 +23694,7 @@ Generated by [AVA](https://avajs.dev).
             31,
           ],
           fixInfo: null,
-          lineNumber: 198,
+          lineNumber: 216,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23710,7 +23710,7 @@ Generated by [AVA](https://avajs.dev).
             36,
           ],
           fixInfo: null,
-          lineNumber: 200,
+          lineNumber: 218,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23726,7 +23726,7 @@ Generated by [AVA](https://avajs.dev).
             28,
           ],
           fixInfo: null,
-          lineNumber: 202,
+          lineNumber: 220,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23742,7 +23742,7 @@ Generated by [AVA](https://avajs.dev).
             18,
           ],
           fixInfo: null,
-          lineNumber: 204,
+          lineNumber: 222,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23762,7 +23762,7 @@ Generated by [AVA](https://avajs.dev).
             editColumn: 11,
             insertText: '#HREFandID',
           },
-          lineNumber: 206,
+          lineNumber: 224,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23778,7 +23778,7 @@ Generated by [AVA](https://avajs.dev).
             34,
           ],
           fixInfo: null,
-          lineNumber: 208,
+          lineNumber: 226,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23794,7 +23794,7 @@ Generated by [AVA](https://avajs.dev).
             34,
           ],
           fixInfo: null,
-          lineNumber: 210,
+          lineNumber: 228,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23810,7 +23810,7 @@ Generated by [AVA](https://avajs.dev).
             39,
           ],
           fixInfo: null,
-          lineNumber: 212,
+          lineNumber: 230,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23823,7 +23823,7 @@ Generated by [AVA](https://avajs.dev).
           errorDetail: null,
           errorRange: null,
           fixInfo: null,
-          lineNumber: 214,
+          lineNumber: 232,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23839,7 +23839,7 @@ Generated by [AVA](https://avajs.dev).
             28,
           ],
           fixInfo: null,
-          lineNumber: 219,
+          lineNumber: 237,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23859,7 +23859,7 @@ Generated by [AVA](https://avajs.dev).
             editColumn: 9,
             insertText: '#valid-fragments',
           },
-          lineNumber: 223,
+          lineNumber: 241,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23879,7 +23879,7 @@ Generated by [AVA](https://avajs.dev).
             editColumn: 12,
             insertText: '#namedlink',
           },
-          lineNumber: 225,
+          lineNumber: 243,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23892,7 +23892,7 @@ Generated by [AVA](https://avajs.dev).
           errorDetail: 'Expected: #namedlink; Actual: #NAMEDLINK',
           errorRange: null,
           fixInfo: null,
-          lineNumber: 227,
+          lineNumber: 245,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23912,7 +23912,7 @@ Generated by [AVA](https://avajs.dev).
             editColumn: 13,
             insertText: '#idlink',
           },
-          lineNumber: 232,
+          lineNumber: 250,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23928,7 +23928,7 @@ Generated by [AVA](https://avajs.dev).
             26,
           ],
           fixInfo: null,
-          lineNumber: 267,
+          lineNumber: 285,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23944,7 +23944,7 @@ Generated by [AVA](https://avajs.dev).
             26,
           ],
           fixInfo: null,
-          lineNumber: 269,
+          lineNumber: 287,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23960,7 +23960,7 @@ Generated by [AVA](https://avajs.dev).
             20,
           ],
           fixInfo: null,
-          lineNumber: 271,
+          lineNumber: 289,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23976,7 +23976,7 @@ Generated by [AVA](https://avajs.dev).
             23,
           ],
           fixInfo: null,
-          lineNumber: 273,
+          lineNumber: 291,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -23992,7 +23992,7 @@ Generated by [AVA](https://avajs.dev).
             22,
           ],
           fixInfo: null,
-          lineNumber: 275,
+          lineNumber: 293,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -24008,7 +24008,7 @@ Generated by [AVA](https://avajs.dev).
             42,
           ],
           fixInfo: null,
-          lineNumber: 277,
+          lineNumber: 295,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -24024,7 +24024,7 @@ Generated by [AVA](https://avajs.dev).
             21,
           ],
           fixInfo: null,
-          lineNumber: 279,
+          lineNumber: 297,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -24040,7 +24040,139 @@ Generated by [AVA](https://avajs.dev).
             21,
           ],
           fixInfo: null,
-          lineNumber: 281,
+          lineNumber: 299,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
+        {
+          errorContext: '[Invalid](#l7)',
+          errorDetail: null,
+          errorRange: [
+            1,
+            14,
+          ],
+          fixInfo: null,
+          lineNumber: 301,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
+        {
+          errorContext: '[Invalid](#L12-abc)',
+          errorDetail: 'Expected: #l12-abc; Actual: #L12-abc',
+          errorRange: [
+            1,
+            19,
+          ],
+          fixInfo: {
+            deleteCount: 8,
+            editColumn: 11,
+            insertText: '#l12-abc',
+          },
+          lineNumber: 303,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
+        {
+          errorContext: '[Invalid](#L7abc)',
+          errorDetail: null,
+          errorRange: [
+            1,
+            17,
+          ],
+          fixInfo: null,
+          lineNumber: 305,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
+        {
+          errorContext: '[Invalid](#L)',
+          errorDetail: null,
+          errorRange: [
+            1,
+            13,
+          ],
+          fixInfo: null,
+          lineNumber: 307,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
+        {
+          errorContext: '[Invalid](#L30C)',
+          errorDetail: null,
+          errorRange: [
+            1,
+            16,
+          ],
+          fixInfo: null,
+          lineNumber: 309,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
+        {
+          errorContext: '[Invalid](#L30L12)',
+          errorDetail: null,
+          errorRange: [
+            1,
+            18,
+          ],
+          fixInfo: null,
+          lineNumber: 311,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
+        {
+          errorContext: '[Invalid](#L30C11-)',
+          errorDetail: null,
+          errorRange: [
+            1,
+            19,
+          ],
+          fixInfo: null,
+          lineNumber: 313,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
+        {
+          errorContext: '[Invalid](#L30C11-L31C)',
+          errorDetail: null,
+          errorRange: [
+            1,
+            23,
+          ],
+          fixInfo: null,
+          lineNumber: 315,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
           ruleNames: [
@@ -24137,6 +24269,22 @@ Generated by [AVA](https://avajs.dev).
       ␊
       [Valid][escapedref]␊
       ␊
+      [Valid](#L7)␊
+      ␊
+      [Valid](#L123)␊
+      ␊
+      [Valid](#L30C11-L31C9)␊
+      ␊
+      [Valid](#L30C11)␊
+      ␊
+      [Valid](#L30C11-L31)␊
+      ␊
+      [Valid](#L30C11-L31)␊
+      ␊
+      [Valid](#L30-L31)␊
+      ␊
+      [Valid](#l12-abc)␊
+      ␊
       ### Valid H3 Heading␊
       ␊
       Text␊
@@ -24222,6 +24370,8 @@ Generated by [AVA](https://avajs.dev).
       ␊
       ### Valid Heading\\-With\\_Embedded\\_Escaping␊
       ␊
+      ### L12 ABC␊
+      ␊
       <a name="namedlink"></a>␊
       ␊
       <a id = idlink></a>␊
@@ -24331,6 +24481,22 @@ Generated by [AVA](https://avajs.dev).
       ␊
       [Invalid](#uppercase) {MD051}␊
       ␊
+      [Invalid](#l7) {MD051}␊
+      ␊
+      [Invalid](#l12-abc) {MD051}␊
+      ␊
+      [Invalid](#L7abc) {MD051}␊
+      ␊
+      [Invalid](#L) {MD051}␊
+      ␊
+      [Invalid](#L30C) {MD051}␊
+      ␊
+      [Invalid](#L30L12) {MD051}␊
+      ␊
+      [Invalid](#L30C11-) {MD051}␊
+      ␊
+      [Invalid](#L30C11-L31C) {MD051}␊
+      ␊
       <!-- markdownlint-configure-file {␊
         "emphasis-style": false,␊
         "heading-style": false,␊