From cb61e0d5bd0d53a1a57ebf4693ebea81549c52d3 Mon Sep 17 00:00:00 2001
From: Johannes Rieken <johannes.rieken@gmail.com>
Date: Tue, 10 Mar 2026 18:57:33 +0100
Subject: [PATCH] Fix source path duplication in NLS plugin source maps and add
 corresponding test (#300487)

---
 build/next/nls-plugin.ts              |  6 +++++-
 build/next/test/nls-sourcemap.test.ts | 22 ++++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/build/next/nls-plugin.ts b/build/next/nls-plugin.ts
index 9f3bfa01e35..e2b19f7d7f1 100644
--- a/build/next/nls-plugin.ts
+++ b/build/next/nls-plugin.ts
@@ -427,7 +427,11 @@ export function nlsPlugin(options: NLSPluginOptions): esbuild.Plugin {
 					// back to the original. Embed it inline so esbuild composes it
 					// with its own bundle source map, making the final map point to
 					// the original TS source.
-					const sourceName = relativePath.replace(/\\/g, '/');
+					// This inline source map is resolved relative to esbuild's sourcefile
+					// for args.path. Using the full repo-relative path here makes esbuild
+					// resolve it against the file's own directory, which duplicates the
+					// directory segments in the final bundled source map.
+					const sourceName = path.basename(args.path);
 					const sourcemap = generateNLSSourceMap(source, sourceName, edits);
 					const encodedMap = Buffer.from(sourcemap).toString('base64');
 					const contentsWithMap = code + `\n//# sourceMappingURL=data:application/json;base64,${encodedMap}\n`;
diff --git a/build/next/test/nls-sourcemap.test.ts b/build/next/test/nls-sourcemap.test.ts
index 09bad2f5c27..c3aad2c80dc 100644
--- a/build/next/test/nls-sourcemap.test.ts
+++ b/build/next/test/nls-sourcemap.test.ts
@@ -220,6 +220,28 @@ suite('NLS plugin source maps', () => {
 		}
 	});
 
+	test('NLS-affected nested file keeps a non-duplicated source path', async () => {
+		const source = [
+			'import { localize } from "../../vs/nls";',
+			'export const msg = localize("myKey", "Hello World");',
+		].join('\n');
+
+		const { mapJson, cleanup } = await bundleWithNLS(
+			{ 'nested/deep/file.ts': source },
+			'nested/deep/file.ts',
+		);
+
+		try {
+			const sources: string[] = mapJson.sources ?? [];
+			const nestedSource = sources.find((s: string) => s.endsWith('/nested/deep/file.ts'));
+			assert.ok(nestedSource, 'Should find nested/deep/file.ts in sources');
+			assert.ok(!nestedSource.includes('/nested/deep/nested/deep/file.ts'),
+				`Source path should not duplicate directory segments. Actual: ${nestedSource}`);
+		} finally {
+			cleanup();
+		}
+	});
+
 	test('line mapping correct for code after localize calls', async () => {
 		const source = [
 			'import { localize } from "../vs/nls";',                         // 1