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/md052.js

@@ -0,0 +1,35 @@
+// @ts-check
+
+"use strict";
+
+const { addError } = require("../helpers");
+const { referenceLinkImageData } = require("./cache");
+
+module.exports = {
+  "names": [ "MD052", "reference-links-images" ],
+  "description":
+    "Reference links and images should use a label that is defined",
+  "tags": [ "images", "links" ],
+  "function": function MD052(params, onError) {
+    const { lines } = params;
+    const { references, definitions } = referenceLinkImageData();
+    // Look for links/images that use an undefined link reference
+    for (const reference of references.entries()) {
+      const [ label, datas ] = reference;
+      if (!definitions.has(label)) {
+        for (const data of datas) {
+          const [ lineIndex, index, length ] = data;
+          // Context will be incomplete if reporting for a multi-line link
+          const context = lines[lineIndex].slice(index, index + length);
+          addError(
+            onError,
+            lineIndex + 1,
+            `Missing link or image reference definition: "${label}"`,
+            context,
+            [ index + 1, context.length ]
+          );
+        }
+      }
+    }
+  }
+};