Update MD051/link-fragments to identify and fix scenarios where the link fragment has the wrong case (fixes #605).

demo/markdownlint-browser.js

@@ -1247,7 +1247,7 @@ module.exports.fixableRuleNames = [
     "MD011", "MD012", "MD014", "MD018", "MD019", "MD020",
     "MD021", "MD022", "MD023", "MD026", "MD027", "MD030",
     "MD031", "MD032", "MD034", "MD037", "MD038", "MD039",
-    "MD044", "MD047", "MD049", "MD050", "MD053"
+    "MD044", "MD047", "MD049", "MD050", "MD051", "MD053"
 ];
 module.exports.homepage = "https://github.com/DavidAnson/markdownlint";
 module.exports.version = "0.26.2";
@@ -4705,7 +4705,7 @@ module.exports = [
 "use strict";
 // @ts-check
 
-const { addError, escapeForRegExp, filterTokens, forEachInlineChild, forEachHeading, htmlElementRe } = __webpack_require__(/*! ../helpers */ "../helpers/helpers.js");
+const { addError, addErrorDetailIf, escapeForRegExp, filterTokens, forEachInlineChild, forEachHeading, htmlElementRe } = __webpack_require__(/*! ../helpers */ "../helpers/helpers.js");
 // Regular expression for identifying HTML anchor names
 const idRe = /\sid\s*=\s*['"]?([^'"\s>]+)/iu;
 const nameRe = /\sname\s*=\s*['"]?([^'"\s>]+)/iu;
@@ -4767,12 +4767,31 @@ module.exports = {
             if (id && (id.length > 1) && (id[0] === "#") && !fragments.has(id)) {
                 let context = id;
                 let range = null;
+                let fixInfo = null;
                 const match = line.match(new RegExp(`\\[.*?\\]\\(${escapeForRegExp(context)}\\)`));
                 if (match) {
-                    context = match[0];
+                    [context] = match;
-                    range = [match.index + 1, match[0].length];
+                    const index = match.index;
+                    const length = context.length;
+                    range = [index + 1, length];
+                    fixInfo = {
+                        "editColumn": index + (length - id.length),
+                        "deleteCount": id.length,
+                        "insertText": null
+                    };
+                }
+                const idLower = id.toLowerCase();
+                const mixedCaseKey = [...fragments.keys()]
+                    .find((key) => idLower === key.toLowerCase());
+                if (mixedCaseKey) {
+                    (fixInfo || {}).insertText = mixedCaseKey;
+                    addErrorDetailIf(onError, lineNumber, mixedCaseKey, id, undefined, context, range, fixInfo);
+                }
+                else {
+                    addError(onError, lineNumber, undefined, context, 
+                    // @ts-ignore
+                    range);
                 }
-                addError(onError, lineNumber, undefined, context, range);
             }
         });
     }

doc/Rules.md

@@ -2141,6 +2141,8 @@ Tags: `links`
 
 Aliases: `link-fragments`
 
+Fixable: Most violations can be fixed by tooling
+
 This rule is triggered when a link fragment does not match any of the fragments
 that are automatically generated for headings in a document:
 

doc/md051.md

@@ -4,6 +4,8 @@ Tags: `links`
 
 Aliases: `link-fragments`
 
+Fixable: Most violations can be fixed by tooling
+
 This rule is triggered when a link fragment does not match any of the fragments
 that are automatically generated for headings in a document:
 

lib/constants.js

@@ -8,7 +8,7 @@ module.exports.fixableRuleNames = [
   "MD011", "MD012", "MD014", "MD018", "MD019", "MD020",
   "MD021", "MD022", "MD023", "MD026", "MD027", "MD030",
   "MD031", "MD032", "MD034", "MD037", "MD038", "MD039",
-  "MD044", "MD047", "MD049", "MD050", "MD053"
+  "MD044", "MD047", "MD049", "MD050", "MD051", "MD053"
 ];
 module.exports.homepage = "https://github.com/DavidAnson/markdownlint";
 module.exports.version = "0.26.2";

lib/md051.js

@@ -2,8 +2,8 @@
 
 "use strict";
 
-const { addError, escapeForRegExp, filterTokens, forEachInlineChild,
+const { addError, addErrorDetailIf, escapeForRegExp, filterTokens,
-  forEachHeading, htmlElementRe } = require("../helpers");
+  forEachInlineChild, forEachHeading, htmlElementRe } = require("../helpers");
 
 // Regular expression for identifying HTML anchor names
 const idRe = /\sid\s*=\s*['"]?([^'"\s>]+)/iu;
@@ -73,14 +73,46 @@ module.exports = {
       if (id && (id.length > 1) && (id[0] === "#") && !fragments.has(id)) {
         let context = id;
         let range = null;
+        let fixInfo = null;
         const match = line.match(
           new RegExp(`\\[.*?\\]\\(${escapeForRegExp(context)}\\)`)
         );
         if (match) {
-          context = match[0];
+          [ context ] = match;
-          range = [ match.index + 1, match[0].length ];
+          const index = match.index;
+          const length = context.length;
+          range = [ index + 1, length ];
+          fixInfo = {
+            "editColumn": index + (length - id.length),
+            "deleteCount": id.length,
+            "insertText": null
+          };
+        }
+        const idLower = id.toLowerCase();
+        const mixedCaseKey = [ ...fragments.keys() ]
+          .find((key) => idLower === key.toLowerCase());
+        if (mixedCaseKey) {
+          (fixInfo || {}).insertText = mixedCaseKey;
+          addErrorDetailIf(
+            onError,
+            lineNumber,
+            mixedCaseKey,
+            id,
+            undefined,
+            context,
+            range,
+            fixInfo
+          );
+        } else {
+          addError(
+            onError,
+            lineNumber,
+            undefined,
+            context,
+            // @ts-ignore
+            range
+          );
         }
-        addError(onError, lineNumber, undefined, context, range);
       }
     });
   }

test/link-fragments.md

@@ -161,6 +161,16 @@ Text
 
 [badref]: #missing
 
+## Inconsistent Case Fragments
+
+[Title](#Valid-Fragments) {MD051}
+
+[ALL CAPS](#NAMEDLINK) {MD051}
+
+[MiXeD][mixedref] {MD051}
+
+[mixedref]: #idLINK
+
 <!-- markdownlint-configure-file {
   "emphasis-style": false,
   "heading-style": false,

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

@@ -21814,12 +21814,16 @@ Generated by [AVA](https://avajs.dev).
         },
         {
           errorContext: '[Invalid](#hrefandid)',
-          errorDetail: null,
+          errorDetail: 'Expected: #HREFandID; Actual: #hrefandid',
           errorRange: [
             1,
             21,
           ],
-          fixInfo: null,
+          fixInfo: {
+            deleteCount: 10,
+            editColumn: 11,
+            insertText: '#HREFandID',
+          },
           lineNumber: 152,
           ruleDescription: 'Link fragments should be valid',
           ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
@@ -21889,6 +21893,59 @@ Generated by [AVA](https://avajs.dev).
             'link-fragments',
           ],
         },
+        {
+          errorContext: '[Title](#Valid-Fragments)',
+          errorDetail: 'Expected: #valid-fragments; Actual: #Valid-Fragments',
+          errorRange: [
+            1,
+            25,
+          ],
+          fixInfo: {
+            deleteCount: 16,
+            editColumn: 9,
+            insertText: '#valid-fragments',
+          },
+          lineNumber: 166,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
+        {
+          errorContext: '[ALL CAPS](#NAMEDLINK)',
+          errorDetail: 'Expected: #namedlink; Actual: #NAMEDLINK',
+          errorRange: [
+            1,
+            22,
+          ],
+          fixInfo: {
+            deleteCount: 10,
+            editColumn: 12,
+            insertText: '#namedlink',
+          },
+          lineNumber: 168,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
+        {
+          errorContext: '#idLINK',
+          errorDetail: 'Expected: #idlink; Actual: #idLINK',
+          errorRange: null,
+          fixInfo: null,
+          lineNumber: 170,
+          ruleDescription: 'Link fragments should be valid',
+          ruleInformation: 'https://github.com/DavidAnson/markdownlint/blob/v0.0.0/doc/md051.md',
+          ruleNames: [
+            'MD051',
+            'link-fragments',
+          ],
+        },
       ],
       fixed: `# Valid/Invalid Link Fragments␊
       ␊
@@ -22041,7 +22098,7 @@ Generated by [AVA](https://avajs.dev).
       ␊
       [Invalid](#myname) {MD051}␊
       ␊
-      [Invalid](#hrefandid) {MD051}␊
+      [Invalid](#HREFandID) {MD051}␊
       ␊
       [Invalid](#name-for-other-element) {MD051}␊
       ␊
@@ -22053,6 +22110,16 @@ Generated by [AVA](https://avajs.dev).
       ␊
       [badref]: #missing␊
       ␊
+      ## Inconsistent Case Fragments␊
+      ␊
+      [Title](#valid-fragments) {MD051}␊
+      ␊
+      [ALL CAPS](#namedlink) {MD051}␊
+      ␊
+      [MiXeD][mixedref] {MD051}␊
+      ␊
+      [mixedref]: #idLINK␊
+      ␊
       <!-- markdownlint-configure-file {␊
         "emphasis-style": false,␊
         "heading-style": false,␊