Remove helpers.deepFreeze and call Object.freeze only on things that need it for ~11% time reduction measured via profile-fixture.mjs on Apple Silicon M1.

demo/markdownlint-browser.js

@@ -1113,27 +1113,6 @@ function getNextChildToken(parentToken, childToken, nextType, nextNextType) {
     return null;
 }
 module.exports.getNextChildToken = getNextChildToken;
-/**
- * Calls Object.freeze() on an object and its children.
- *
- * @param {Object} obj Object to deep freeze.
- * @returns {Object} Object passed to the function.
- */
-function deepFreeze(obj) {
-    const pending = [obj];
-    let current = null;
-    while ((current = pending.shift())) {
-        Object.freeze(current);
-        for (const name of Object.getOwnPropertyNames(current)) {
-            const value = current[name];
-            if (value && (typeof value === "object")) {
-                pending.push(value);
-            }
-        }
-    }
-    return obj;
-}
-module.exports.deepFreeze = deepFreeze;
 /**
  * Expands a path with a tilde to an absolute path.
  *
@@ -1442,13 +1421,37 @@ function removeFrontMatter(content, frontMatter) {
     };
 }
 /**
- * Annotate tokens with line/lineNumber.
+ * Freeze all freeze-able members of a token and its children.
+ *
+ * @param {MarkdownItToken} token A markdown-it token.
+ * @returns {void}
+ */
+function freezeToken(token) {
+    if (token.attrs) {
+        for (const attr of token.attrs) {
+            Object.freeze(attr);
+        }
+        Object.freeze(token.attrs);
+    }
+    if (token.children) {
+        for (const child of token.children) {
+            freezeToken(child);
+        }
+        Object.freeze(token.children);
+    }
+    if (token.map) {
+        Object.freeze(token.map);
+    }
+    Object.freeze(token);
+}
+/**
+ * Annotate tokens with line/lineNumber and freeze them.
  *
  * @param {MarkdownItToken[]} tokens Array of markdown-it tokens.
  * @param {string[]} lines Lines of Markdown content.
  * @returns {void}
  */
-function annotateTokens(tokens, lines) {
+function annotateAndFreezeTokens(tokens, lines) {
     let trMap = null;
     for (const token of tokens) {
         // Provide missing maps for table content
@@ -1474,13 +1477,15 @@ function annotateTokens(tokens, lines) {
             while (token.map[1] && !((lines[token.map[1] - 1] || "").trim())) {
                 token.map[1]--;
             }
-            // Annotate children with lineNumber
+        }
+        // Annotate children with lineNumber
+        if (token.children) {
             let lineNumber = token.lineNumber;
             const codeSpanExtraLines = [];
             helpers.forEachInlineCodeSpan(token.content, function handleInlineCodeSpan(code) {
                 codeSpanExtraLines.push(code.split(helpers.newLineRe).length - 1);
             });
-            for (const child of (token.children || [])) {
+            for (const child of token.children) {
                 child.lineNumber = lineNumber;
                 child.line = lines[lineNumber - 1];
                 if ((child.type === "softbreak") || (child.type === "hardbreak")) {
@@ -1491,7 +1496,9 @@ function annotateTokens(tokens, lines) {
                 }
             }
         }
+        freezeToken(token);
     }
+    Object.freeze(tokens);
 }
 /**
  * Map rule names/tags to canonical rule name.
@@ -1741,14 +1748,14 @@ function lintContent(ruleList, name, content, md, config, configParsers, frontMa
     // Parse content into tokens and lines
     const tokens = md.parse(content, {});
     const lines = content.split(helpers.newLineRe);
-    annotateTokens(tokens, lines);
+    annotateAndFreezeTokens(tokens, lines);
-    // Create parameters for rules
+    // Create (frozen) parameters for rules
-    const paramsBase = helpers.deepFreeze({
+    const paramsBase = {
         name,
         tokens,
-        lines,
+        "lines": Object.freeze(lines),
-        frontMatterLines
+        "frontMatterLines": Object.freeze(frontMatterLines)
-    });
+    };
     const lineMetadata = helpers.getLineMetadata(paramsBase);
     const codeBlockAndSpanRanges = helpers.codeBlockAndSpanRanges(paramsBase, lineMetadata);
     const flattenedLists = helpers.flattenLists(paramsBase.tokens);

helpers/helpers.js

@@ -1153,28 +1153,6 @@ function getNextChildToken(parentToken, childToken, nextType, nextNextType) {
 }
 module.exports.getNextChildToken = getNextChildToken;
 
-/**
- * Calls Object.freeze() on an object and its children.
- *
- * @param {Object} obj Object to deep freeze.
- * @returns {Object} Object passed to the function.
- */
-function deepFreeze(obj) {
-  const pending = [ obj ];
-  let current = null;
-  while ((current = pending.shift())) {
-    Object.freeze(current);
-    for (const name of Object.getOwnPropertyNames(current)) {
-      const value = current[name];
-      if (value && (typeof value === "object")) {
-        pending.push(value);
-      }
-    }
-  }
-  return obj;
-}
-module.exports.deepFreeze = deepFreeze;
-
 /**
  * Expands a path with a tilde to an absolute path.
  *

lib/markdownlint.js

@@ -191,13 +191,38 @@ function removeFrontMatter(content, frontMatter) {
 }
 
 /**
- * Annotate tokens with line/lineNumber.
+ * Freeze all freeze-able members of a token and its children.
+ *
+ * @param {MarkdownItToken} token A markdown-it token.
+ * @returns {void}
+ */
+function freezeToken(token) {
+  if (token.attrs) {
+    for (const attr of token.attrs) {
+      Object.freeze(attr);
+    }
+    Object.freeze(token.attrs);
+  }
+  if (token.children) {
+    for (const child of token.children) {
+      freezeToken(child);
+    }
+    Object.freeze(token.children);
+  }
+  if (token.map) {
+    Object.freeze(token.map);
+  }
+  Object.freeze(token);
+}
+
+/**
+ * Annotate tokens with line/lineNumber and freeze them.
  *
  * @param {MarkdownItToken[]} tokens Array of markdown-it tokens.
  * @param {string[]} lines Lines of Markdown content.
  * @returns {void}
  */
-function annotateTokens(tokens, lines) {
+function annotateAndFreezeTokens(tokens, lines) {
   let trMap = null;
   for (const token of tokens) {
     // Provide missing maps for table content
@@ -222,7 +247,9 @@ function annotateTokens(tokens, lines) {
       while (token.map[1] && !((lines[token.map[1] - 1] || "").trim())) {
         token.map[1]--;
       }
-      // Annotate children with lineNumber
+    }
+    // Annotate children with lineNumber
+    if (token.children) {
       let lineNumber = token.lineNumber;
       const codeSpanExtraLines = [];
       helpers.forEachInlineCodeSpan(
@@ -231,7 +258,7 @@ function annotateTokens(tokens, lines) {
           codeSpanExtraLines.push(code.split(helpers.newLineRe).length - 1);
         }
       );
-      for (const child of (token.children || [])) {
+      for (const child of token.children) {
         child.lineNumber = lineNumber;
         child.line = lines[lineNumber - 1];
         if ((child.type === "softbreak") || (child.type === "hardbreak")) {
@@ -241,7 +268,9 @@ function annotateTokens(tokens, lines) {
         }
       }
     }
+    freezeToken(token);
   }
+  Object.freeze(tokens);
 }
 
 /**
@@ -532,14 +561,14 @@ function lintContent(
   // Parse content into tokens and lines
   const tokens = md.parse(content, {});
   const lines = content.split(helpers.newLineRe);
-  annotateTokens(tokens, lines);
+  annotateAndFreezeTokens(tokens, lines);
-  // Create parameters for rules
+  // Create (frozen) parameters for rules
-  const paramsBase = helpers.deepFreeze({
+  const paramsBase = {
     name,
     tokens,
-    lines,
+    "lines": Object.freeze(lines),
-    frontMatterLines
+    "frontMatterLines": Object.freeze(frontMatterLines)
-  });
+  };
   const lineMetadata =
     helpers.getLineMetadata(paramsBase);
   const codeBlockAndSpanRanges =

test/markdownlint-test-custom-rules.js

@@ -1200,6 +1200,39 @@ test("customRulesAsyncThrowsInSyncContext", (t) => {
   );
 });
 
+test("customRulesParamsAreFrozen", (t) => {
+  const options = {
+    "customRules": [
+      {
+        "names": [ "name" ],
+        "description": "description",
+        "tags": [ "tag" ],
+        "function":
+          (params) => {
+            const pending = [ params ];
+            let current = null;
+            while ((current = pending.shift())) {
+              t.true(Object.isFrozen(current) || (current === params));
+              for (const name of Object.getOwnPropertyNames(current)) {
+                const value = current[name];
+                if (value && (typeof value === "object")) {
+                  pending.push(value);
+                }
+              }
+            }
+          }
+      }
+    ],
+    "files": [
+      "CONTRIBUTING.md",
+      "README.md",
+      "doc/CustomRules.md",
+      "doc/Rules.md"
+    ]
+  };
+  return markdownlint.promises.markdownlint(options).then(() => null);
+});
+
 test("customRulesParamsAreStable", (t) => {
   t.plan(4);
   const config1 = { "value1": 10 };

test/markdownlint-test-helpers.js

@@ -953,40 +953,6 @@ test("applyFixes", (t) => {
   }
 });
 
-test("deepFreeze", (t) => {
-  t.plan(6);
-  const obj = {
-    "prop": true,
-    "func": () => true,
-    "sub": {
-      "prop": [ 1 ],
-      "sub": {
-        "prop": "one"
-      }
-    }
-  };
-  t.is(helpers.deepFreeze(obj), obj, "Did not return object.");
-  for (const scenario of [
-    () => {
-      obj.prop = false;
-    },
-    () => {
-      obj.func = () => false;
-    },
-    () => {
-      obj.sub.prop = [];
-    },
-    () => {
-      obj.sub.prop[0] = 0;
-    },
-    () => {
-      obj.sub.sub.prop = "zero";
-    }
-  ]) {
-    t.throws(scenario, null, "Assigned to frozen object.");
-  }
-});
-
 test("forEachLink", (t) => {
   t.plan(291);
   const testCases = [