Add MD052/reference-links-images and MD053/link-image-reference-definitions for reporting issues with link and image references (fixes #144, fixes #390, fixes #425, fixes #456).

lib/md053.js

@@ -0,0 +1,52 @@
+// @ts-check
+
+"use strict";
+
+const { addError, ellipsify, linkReferenceDefinitionRe } =
+  require("../helpers");
+const { referenceLinkImageData } = require("./cache");
+
+module.exports = {
+  "names": [ "MD053", "link-image-reference-definitions" ],
+  "description": "Link and image reference definitions should be needed",
+  "tags": [ "images", "links" ],
+  "function": function MD053(params, onError) {
+    const { lines } = params;
+    const { references, shortcuts, definitions, duplicateDefinitions } =
+      referenceLinkImageData();
+    const singleLineDefinition = (line) => (
+      line.replace(linkReferenceDefinitionRe, "").trim().length > 0
+    );
+    const deleteFixInfo = {
+      "deleteCount": -1
+    };
+    // Look for unused link references (unreferenced by any link/image)
+    for (const definition of definitions.entries()) {
+      const [ label, lineIndex ] = definition;
+      if (!references.has(label) && !shortcuts.has(label)) {
+        const line = lines[lineIndex];
+        addError(
+          onError,
+          lineIndex + 1,
+          `Unused link or image reference definition: "${label}"`,
+          ellipsify(line),
+          [ 1, line.length ],
+          singleLineDefinition(line) ? deleteFixInfo : 0
+        );
+      }
+    }
+    // Look for duplicate link references (defined more than once)
+    for (const duplicateDefinition of duplicateDefinitions) {
+      const [ label, lineIndex ] = duplicateDefinition;
+      const line = lines[lineIndex];
+      addError(
+        onError,
+        lineIndex + 1,
+        `Duplicate link or image reference definition: "${label}"`,
+        ellipsify(line),
+        [ 1, line.length ],
+        singleLineDefinition(line) ? deleteFixInfo : 0
+      );
+    }
+  }
+};