From 9e3e6763fa411257f3ebf76929be63434b71a99f Mon Sep 17 00:00:00 2001
From: bcoe <bencoe@google.com>
Date: Sun, 23 Feb 2020 19:19:15 -0800
Subject: [PATCH] module: port source map sort logic from chromium

Digging in to the delta between V8's source map library, and chromium's
the most significant difference that jumped out at me was that we were
failing to sort generated columns. Since negative offsets are not
restricted in the spec, this can lead to bugs.

fixes: #31286

PR-URL: https://github.com/nodejs/node/pull/31927
Fixes: https://github.com/nodejs/node/issues/31286
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
---
 lib/internal/source_map/source_map.js | 21 +++++++++++++++++++--
 test/parallel/test-source-map-api.js  | 25 +++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/lib/internal/source_map/source_map.js b/lib/internal/source_map/source_map.js
index c440dffdf81913..acff068be2a6e7 100644
--- a/lib/internal/source_map/source_map.js
+++ b/lib/internal/source_map/source_map.js
@@ -152,10 +152,12 @@ class SourceMap {
    * @param {SourceMapV3} mappingPayload
    */
   #parseMappingPayload = () => {
-    if (this.#payload.sections)
+    if (this.#payload.sections) {
       this.#parseSections(this.#payload.sections);
-    else
+    } else {
       this.#parseMap(this.#payload, 0, 0);
+    }
+    this.#mappings.sort(compareSourceMapEntry);
   }
 
   /**
@@ -321,6 +323,21 @@ function cloneSourceMapV3(payload) {
   return payload;
 }
 
+/**
+ * @param {Array} entry1 source map entry [lineNumber, columnNumber, sourceURL,
+ *  sourceLineNumber, sourceColumnNumber]
+ * @param {Array} entry2 source map entry.
+ * @return {number}
+ */
+function compareSourceMapEntry(entry1, entry2) {
+  const [lineNumber1, columnNumber1] = entry1;
+  const [lineNumber2, columnNumber2] = entry2;
+  if (lineNumber1 !== lineNumber2) {
+    return lineNumber1 - lineNumber2;
+  }
+  return columnNumber1 - columnNumber2;
+}
+
 module.exports = {
   SourceMap
 };
diff --git a/test/parallel/test-source-map-api.js b/test/parallel/test-source-map-api.js
index 2bfbc08809e9a1..60bbb661e1c801 100644
--- a/test/parallel/test-source-map-api.js
+++ b/test/parallel/test-source-map-api.js
@@ -124,3 +124,28 @@ const { readFileSync } = require('fs');
     assert.strictEqual(originalColumn, knownDecodings[column]);
   }
 }
+
+// Test that generated columns are sorted when a negative offset is
+// observed, see: https://github.com/mozilla/source-map/pull/92
+{
+  function makeMinimalMap(generatedColumns, originalColumns) {
+    return {
+      sources: ['test.js'],
+      // Mapping from the 0th line, ${g}th column of the output file to the 0th
+      // source file, 0th line, ${column}th column.
+      mappings: generatedColumns.map((g, i) => `${g}AA${originalColumns[i]}`)
+        .join(',')
+    };
+  }
+  // U = 10
+  // F = -2
+  // A = 0
+  // E = 2
+  const sourceMap = new SourceMap(makeMinimalMap(
+    ['U', 'F', 'F'],
+    ['A', 'E', 'E']
+  ));
+  assert.strictEqual(sourceMap.findEntry(0, 6).originalColumn, 4);
+  assert.strictEqual(sourceMap.findEntry(0, 8).originalColumn, 2);
+  assert.strictEqual(sourceMap.findEntry(0, 10).originalColumn, 0);
+}