feat: Add type checking

.gitignore

@@ -8,3 +8,4 @@ npm-debug.log
 yarn.lock
 package-lock.json
 pnpm-lock.yaml
+dist

rollup.config.js

@@ -1,3 +1,5 @@
+import copy from "rollup-plugin-copy";
+
 export default {
     input: "src/index.js",
     output: [
@@ -6,5 +8,12 @@ export default {
             format: "esm",
             banner: '// @ts-self-types="./index.d.ts"'
         }
+    ],
+    plugins: [
+        copy({
+            targets: [
+                { src: "src/types.ts", dest: "dist/esm" }
+            ]
+        })
     ]
 };

src/index.js

@@ -9,10 +9,18 @@
 
 import { processor } from "./processor.js";
 
+//-----------------------------------------------------------------------------
+// Type Definitions
+//-----------------------------------------------------------------------------
+
+/** @typedef {import("eslint").Linter.RulesRecord} RulesRecord*/
+/** @typedef {import("eslint").ESLint.Plugin} Plugin */
+
 //-----------------------------------------------------------------------------
 // Exports
 //-----------------------------------------------------------------------------
 
+/** @type {RulesRecord} */
 const rulesConfig = {
 
     // The Markdown parser automatically trims trailing
@@ -36,6 +44,7 @@ const rulesConfig = {
     "unicode-bom": "off"
 };
 
+/** @type {Plugin} */
 const plugin = {
     meta: {
         name: "@eslint/markdown",

src/processor.js

@@ -3,30 +3,30 @@
  * @author Brandon Mills
  */
 
-/**
- * @typedef {import('eslint/lib/shared/types').LintMessage} Message
- * @typedef {Object} ASTNode
- * @property {string} type The type of node.
- * @property {string} [lang] The language that the node is in
- * @typedef {Object} RangeMap
- * @property {number} indent Number of code block indent characters trimmed from
- *     the beginning of the line during extraction.
- * @property {number} js Offset from the start of the code block's range in the
- *     extracted JS.
- * @property {number} md Offset from the start of the code block's range in the
- *     original Markdown.
- * @typedef {Object} BlockBase
- * @property {string} baseIndentText Leading whitespace text for the block.
- * @property {string[]} comments Comments inside of the JavaScript code.
- * @property {RangeMap[]} rangeMap A list of offset-based adjustments, where
- *    lookups are done based on the `js` key, which represents the range in the
- *    linted JS, and the `md` key is the offset delta that, when added to the JS
- *    range, returns the corresponding location in the original Markdown source.
- * @typedef {ASTNode & BlockBase} Block
- */
+//-----------------------------------------------------------------------------
+// Imports
+//-----------------------------------------------------------------------------
 
 import { fromMarkdown } from "mdast-util-from-markdown";
 
+//-----------------------------------------------------------------------------
+// Type Definitions
+//-----------------------------------------------------------------------------
+
+/** @typedef {import("./types.ts").Block} Block */
+/** @typedef {import("./types.ts").RangeMap} RangeMap */
+/** @typedef {import("mdast").Node} Node */
+/** @typedef {import("mdast").Parent} ParentNode */
+/** @typedef {import("mdast").Code} CodeNode */
+/** @typedef {import("mdast").Html} HtmlNode */
+/** @typedef {import("eslint").Linter.LintMessage} Message */
+/** @typedef {import("eslint").Rule.Fix} Fix */
+/** @typedef {import("eslint").AST.Range} Range */
+
+//-----------------------------------------------------------------------------
+// Helpers
+//-----------------------------------------------------------------------------
+
 const UNSATISFIABLE_RULES = new Set([
     "eol-last", // The Markdown parser strips trailing newlines in code fences
     "unicode-bom" // Code blocks will begin in the middle of Markdown files
@@ -40,8 +40,8 @@ const blocksCache = new Map();
 
 /**
  * Performs a depth-first traversal of the Markdown AST.
- * @param {ASTNode} node A Markdown AST node.
- * @param {{[key: string]: (node: ASTNode) => void}} callbacks A map of node types to callbacks.
+ * @param {Node} node A Markdown AST node.
+ * @param {{[key: string]: (node?: Node) => void}} callbacks A map of node types to callbacks.
  * @returns {void}
  */
 function traverse(node, callbacks) {
@@ -51,9 +51,11 @@ function traverse(node, callbacks) {
         callbacks["*"]();
     }
 
-    if (typeof node.children !== "undefined") {
-        for (let i = 0; i < node.children.length; i++) {
-            traverse(node.children[i], callbacks);
+    const parent = /** @type {ParentNode} */ (node);
+
+    if (typeof parent.children !== "undefined") {
+        for (let i = 0; i < parent.children.length; i++) {
+            traverse(parent.children[i], callbacks);
         }
     }
 }
@@ -92,7 +94,7 @@ const leadingWhitespaceRegex = /^[>\s]*/u;
 /**
  * Gets the offset for the first column of the node's first line in the
  * original source text.
- * @param {ASTNode} node A Markdown code block AST node.
+ * @param {Node} node A Markdown code block AST node.
  * @returns {number} The offset for the first column of the node's first line.
  */
 function getBeginningOfLineOffset(node) {
@@ -103,7 +105,7 @@ function getBeginningOfLineOffset(node) {
  * Gets the leading text, typically whitespace with possible blockquote chars,
  * used to indent a code block.
  * @param {string} text The text of the file.
- * @param {ASTNode} node A Markdown code block AST node.
+ * @param {Node} node A Markdown code block AST node.
  * @returns {string} The text from the start of the first line to the opening
  *     fence of the code block.
  */
@@ -137,7 +139,7 @@ function getIndentText(text, node) {
  * differences within the line, so the mapping need only provide the offset
  * delta at the beginning of each line.
  * @param {string} text The text of the file.
- * @param {ASTNode} node A Markdown code block AST node.
+ * @param {Node} node A Markdown code block AST node.
  * @param {string[]} comments List of configuration comment strings that will be
  *     inserted at the beginning of the code block.
  * @returns {RangeMap[]} A list of offset-based adjustments, where lookups are
@@ -265,6 +267,12 @@ function preprocess(text, filename) {
         "*"() {
             htmlComments = [];
         },
+
+        /**
+         * Visit a code node.
+         * @param {CodeNode} node The visited node.
+         * @returns {void}
+         */
         code(node) {
             if (node.lang) {
                 const comments = [];
@@ -288,6 +296,12 @@ function preprocess(text, filename) {
                 });
             }
         },
+
+        /**
+         * Visit an HTML node.
+         * @param {HtmlNode} node The visited node.
+         * @returns {void}
+         */
         html(node) {
             const comment = getComment(node.value);
 
@@ -357,7 +371,7 @@ function adjustBlock(block) {
 
         if (message.fix) {
             adjustedFix.fix = {
-                range: message.fix.range.map(range => {
+                range: /** @type {Range} */ (message.fix.range.map(range => {
 
                     // Advance through the block's range map to find the last
                     // matching range by finding the first range too far and
@@ -370,7 +384,7 @@ function adjustBlock(block) {
 
                     // Apply the mapping delta for this range.
                     return range + block.rangeMap[i - 1].md;
-                }),
+                })),
                 text: message.fix.text.replace(/\n/gu, `\n${block.baseIndentText}`)
             };
         }

src/types.ts

@@ -0,0 +1,19 @@
+import type { Node } from "mdast";
+import type { Linter } from "eslint";
+
+
+export interface RangeMap {
+    indent: number;
+    js: number;
+    md: number;
+}
+
+export interface BlockBase {
+    baseIndentText: string;
+    comments: string[];
+    rangeMap: RangeMap[];
+}
+
+export interface Block extends Node, BlockBase {}
+
+export type Message = Linter.LintMessage;

tsconfig.json

@@ -3,6 +3,7 @@
   "compilerOptions": {
     "declaration": true,
     "emitDeclarationOnly": true,
+    "allowImportingTsExtensions": true,
     "allowJs": true,
     "checkJs": true,
     "outDir": "dist/esm",