From 6406f50ab17ab20b08bbe1fda2eb4fbe0fdc5657 Mon Sep 17 00:00:00 2001
From: isaacs <i@izs.me>
Date: Wed, 12 Jul 2023 11:37:32 -0700
Subject: [PATCH] module: add SourceMap.lineLengths

Fix: #48460
PR-URL: https://github.com/nodejs/node/pull/48461
Fixes: https://github.com/nodejs/node/issues/48460
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>
---
 doc/api/module.md                           |  6 +++++-
 lib/internal/source_map/source_map.js       | 16 +++++++++++++++-
 lib/internal/source_map/source_map_cache.js |  2 +-
 test/parallel/test-source-map-api.js        | 12 +++++++++++-
 4 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/doc/api/module.md b/doc/api/module.md
index 19ba0f981cc200..d77b6e29cc7a17 100644
--- a/doc/api/module.md
+++ b/doc/api/module.md
@@ -176,9 +176,10 @@ added:
  - v12.17.0
 -->
 
-#### `new SourceMap(payload)`
+#### `new SourceMap(payload[, { lineLengths }])`
 
 * `payload` {Object}
+* `lineLengths` {number\[]}
 
 Creates a new `sourceMap` instance.
 
@@ -192,6 +193,9 @@ Creates a new `sourceMap` instance.
 * `mappings`: {string}
 * `sourceRoot`: {string}
 
+`lineLengths` is an optional array of the length of each line in the
+generated code.
+
 #### `sourceMap.payload`
 
 * Returns: {Object}
diff --git a/lib/internal/source_map/source_map.js b/lib/internal/source_map/source_map.js
index 3112a026b643e2..9e63eabaacf665 100644
--- a/lib/internal/source_map/source_map.js
+++ b/lib/internal/source_map/source_map.js
@@ -125,12 +125,13 @@ class SourceMap {
   #mappings = [];
   #sources = {};
   #sourceContentByURL = {};
+  #lineLengths = undefined;
 
   /**
    * @constructor
    * @param {SourceMapV3} payload
    */
-  constructor(payload) {
+  constructor(payload, { lineLengths } = { __proto__: null }) {
     if (!base64Map) {
       const base64Digits =
              'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
@@ -140,6 +141,9 @@ class SourceMap {
     }
     this.#payload = cloneSourceMapV3(payload);
     this.#parseMappingPayload();
+    if (ArrayIsArray(lineLengths) && lineLengths.length) {
+      this.#lineLengths = lineLengths;
+    }
   }
 
   /**
@@ -149,6 +153,16 @@ class SourceMap {
     return cloneSourceMapV3(this.#payload);
   }
 
+  /**
+   * @return {number[] | undefined} line lengths of generated source code
+   */
+  get lineLengths() {
+    if (this.#lineLengths) {
+      return ArrayPrototypeSlice(this.#lineLengths);
+    }
+    return undefined;
+  }
+
   #parseMappingPayload = () => {
     if (this.#payload.sections) {
       this.#parseSections(this.#payload.sections);
diff --git a/lib/internal/source_map/source_map_cache.js b/lib/internal/source_map/source_map_cache.js
index ebe0288e436d90..2813da21dfdc63 100644
--- a/lib/internal/source_map/source_map_cache.js
+++ b/lib/internal/source_map/source_map_cache.js
@@ -317,7 +317,7 @@ function findSourceMap(sourceURL) {
   }
   let sourceMap = entry.sourceMap;
   if (sourceMap === undefined) {
-    sourceMap = new SourceMap(entry.data);
+    sourceMap = new SourceMap(entry.data, { lineLengths: entry.lineLengths });
     entry.sourceMap = sourceMap;
   }
   return sourceMap;
diff --git a/test/parallel/test-source-map-api.js b/test/parallel/test-source-map-api.js
index 2c6cf341339a53..8c965891536072 100644
--- a/test/parallel/test-source-map-api.js
+++ b/test/parallel/test-source-map-api.js
@@ -57,6 +57,8 @@ const { readFileSync } = require('fs');
   assert.strictEqual(fileName, originalSource);
   assert.strictEqual(lineNumber, 3);
   assert.strictEqual(columnNumber, 6);
+  assert(Array.isArray(sourceMap.lineLengths));
+  assert(!sourceMap.lineLengths.some((len) => (typeof len !== 'number')));
 }
 
 // findSourceMap() can be used in Error.prepareStackTrace() to lookup
@@ -116,7 +118,10 @@ const { readFileSync } = require('fs');
   const payload = JSON.parse(readFileSync(
     require.resolve('../fixtures/source-map/disk.map'), 'utf8'
   ));
-  const sourceMap = new SourceMap(payload);
+  const lineLengths = readFileSync(
+    require.resolve('../fixtures/source-map/disk.map'), 'utf8'
+  ).replace(/\n$/, '').split('\n').map((l) => l.length);
+  const sourceMap = new SourceMap(payload, { lineLengths });
   const {
     originalLine,
     originalColumn,
@@ -125,6 +130,11 @@ const { readFileSync } = require('fs');
   assert.strictEqual(originalLine, 2);
   assert.strictEqual(originalColumn, 4);
   assert(originalSource.endsWith('disk.js'));
+  const sourceMapLineLengths = sourceMap.lineLengths;
+  for (let i = 0; i < sourceMapLineLengths.length; i++) {
+    assert.strictEqual(sourceMapLineLengths[i], lineLengths[i]);
+  }
+  assert.strictEqual(sourceMapLineLengths.length, lineLengths.length);
   // The stored payload should be a clone:
   assert.strictEqual(payload.mappings, sourceMap.payload.mappings);
   assert.notStrictEqual(payload, sourceMap.payload);