Add new rule

Author: khiga8

src/rules/no-empty-string-alt.js

@@ -0,0 +1,44 @@
+module.exports = {
+  names: ["GH003", "no-empty-string-alt"],
+  description: "Please provide an alternative text for the image.",
+  information: new URL(
+    "https://github.com/github/markdownlint-github/blob/main/docs/rules/GH003-no-empty-string-alt.md",
+  ),
+  tags: ["accessibility", "images"],
+  function: function GH003(params, onError) {
+    const htmlTagsWithImages = params.parsers.markdownit.tokens.filter(
+      (token) => {
+        return token.type === "html_block" && token.content.includes("<img");
+      },
+    );
+    const inlineImages = params.parsers.markdownit.tokens.filter(
+      (token) =>
+        token.type === "inline" &&
+        token.children.some((child) => child.type === "image"),
+    );
+
+    const htmlAltRegex = new RegExp(/alt=""|alt=''/i);
+    const markdownAltRegex = new RegExp(/!\[""\]|!\[''\]/i);
+
+    for (const token of [...htmlTagsWithImages, ...inlineImages]) {
+      const lineRange = token.map;
+      const lineNumber = token.lineNumber;
+      const lines = params.lines.slice(lineRange[0], lineRange[1]);
+
+      for (let i = 0; i < lines.length; i++) {
+        const line = lines[i];
+        let fails;
+        if (token.type === "inline") {
+          fails = markdownAltRegex.test(line);
+        } else {
+          fails = htmlAltRegex.test(line);
+        }
+        if (fails) {
+          onError({
+            lineNumber: lineNumber + i,
+          });
+        }
+      }
+    }
+  },
+};