Skip to content

module: don't read a phantom name on the last mapping segment #63801

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
dusanstanojeviccs wants to merge 1 commit into
base: main
Choose a base branch
from
Open

module: don't read a phantom name on the last mapping segment #63801

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
module: don't read a phantom name on the last mapping segment 
SourceMap#parseMap reads the optional name VLQ guarded only by
!isSeparator(peek()). At the end of the mappings string peek() returns
'', which is not a separator, so the parser decodes a phantom VLQ (0),
keeps the previous nameIndex, and assigns names[nameIndex] to a segment
that has no name field. SourceMap.findEntry() then returns a stale name,
which surfaces as the wrong function name on the bottom global frame of
--enable-source-maps stack traces.

Guard the name read with hasNext() so the phantom field is not read at
end of string. A trailing segment that genuinely carries a name still
has characters left to read, so it is unaffected.

Refs: #63795
Signed-off-by: Dusan Stanojevic <dusan.stanojevic.cs@gmail.com>
  • Loading branch information
@dusanstanojeviccs
dusanstanojeviccs committed Jun 8, 2026
commit 69543f48458d8439e3da9e737dbce1b8060cfb12
3 changes: 2 additions & 1 deletion lib/internal/source_map/source_map.js
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -300,7 +300,8 @@ class SourceMap {
sourceColumnNumber += decodeVLQ(stringCharIterator);

let name;
if (!isSeparator(stringCharIterator.peek())) {
if (stringCharIterator.hasNext() &&
!isSeparator(stringCharIterator.peek())) {
nameIndex += decodeVLQ(stringCharIterator);
name = map.names?.[nameIndex];
}
Expand Down
34 changes: 34 additions & 0 deletions test/parallel/test-source-map-trailing-name.js
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,34 @@
'use strict';
require('../common');
const assert = require('assert');
const { SourceMap } = require('node:module');

// Refs: https://github.com/nodejs/node/issues/63795

// A mapping whose final segment has 4 fields (no name index) must not
// inherit the previous segment's name.
{
const sm = new SourceMap({
version: 3,
sources: ['a.js'],
names: ['foo'],
mappings: 'AAAAA,CAAC',
});

assert.strictEqual(sm.findEntry(0, 0).name, 'foo');
assert.strictEqual(sm.findEntry(0, 1).name, undefined);
}

// A mapping whose final segment legitimately carries a name index must still
// resolve it: the end-of-string guard must not suppress a real trailing name.
{
const sm = new SourceMap({
version: 3,
sources: ['a.js'],
names: ['foo'],
mappings: 'AAAA,CAAAA',
});

assert.strictEqual(sm.findEntry(0, 0).name, undefined);
assert.strictEqual(sm.findEntry(0, 1).name, 'foo');
}
Loading