fix(source map): handle source map in middle of file (#392)

Co-authored-by: Hiroki Osame <hiroki.osame@gmail.com>

src/source-map.ts

@@ -20,10 +20,13 @@ const sourceMapPrefix = '\n//# sourceMappingURL=';
 
 export const stripSourceMap = (code: string) => {
 	const sourceMapIndex = code.indexOf(sourceMapPrefix);
-	if (sourceMapIndex !== -1) {
-		return code.slice(0, sourceMapIndex);
+	if (sourceMapIndex === -1) {
+		return code;
 	}
-	return code;
+
+	const nextNewLine = code.indexOf('\n', sourceMapIndex + sourceMapPrefix.length);
+	const afterSourceMap = nextNewLine === -1 ? '' : code.slice(nextNewLine);
+	return code.slice(0, sourceMapIndex) + afterSourceMap;
 };
 
 const inlineSourceMapPrefix = `${sourceMapPrefix}data:application/json;base64,`;

tests/index.ts

@@ -7,6 +7,7 @@ import { nodeVersions } from './utils/node-versions';
 		await runTestSuite(import('./specs/cli'));
 		await runTestSuite(import('./specs/watch'));
 		await runTestSuite(import('./specs/repl'));
+		await runTestSuite(import('./specs/source-map'));
 
 		for (const nodeVersion of nodeVersions) {
 			const node = await createNode(nodeVersion);

tests/specs/smoke.ts

@@ -2,6 +2,7 @@ import path from 'path';
 import { pathToFileURL } from 'url';
 import { testSuite, expect } from 'manten';
 import { createFixture } from 'fs-fixture';
+import outdent from 'outdent';
 import type { NodeApis } from '../utils/tsx';
 
 const cjsContextCheck = 'typeof module !== \'undefined\'';
@@ -329,10 +330,12 @@ export default testSuite(async ({ describe }, { tsx }: NodeApis) => {
 					const fixture = await createFixture({
 						...files,
 						'package.json': JSON.stringify({ type: packageType }),
-						'import-from-js.js': `
+						'import-from-js.js': outdent`
 						import assert from 'assert';
 						import { expectErrors } from './expect-errors';
 		
+						//# sourceMappingURL=shouldnt affect the file
+
 						// node: prefix
 						import 'node:fs';
 
@@ -453,10 +456,12 @@ export default testSuite(async ({ describe }, { tsx }: NodeApis) => {
 						...files,
 						'package.json': JSON.stringify({ type: packageType }),
 
-						'import-from-ts.ts': `
+						'import-from-ts.ts': outdent`
 						import assert from 'assert';
 						import { expectErrors } from './expect-errors';
 
+						//# sourceMappingURL=shouldnt affect the file
+
 						// node: prefix
 						import 'node:fs';
 

tests/specs/source-map.ts

@@ -0,0 +1,23 @@
+import { testSuite, expect } from 'manten';
+import { stripSourceMap } from '../../src/source-map';
+
+export default testSuite(({ describe }) => {
+	describe('Source Map', ({ describe }) => {
+		describe('stripSourceMap', ({ test }) => {
+			test('end of file, no trailing newline', () => {
+				const file = 'const foo = 1;\n//# sourceMappingURL=foo.js.map';
+				expect(stripSourceMap(file)).toBe('const foo = 1;');
+			});
+
+			test('end of file, with trailing newlines', () => {
+				const file = 'const foo = 1;\n//# sourceMappingURL=foo.js.map\n';
+				expect(stripSourceMap(file)).toBe('const foo = 1;\n');
+			});
+
+			test('middle of file', () => {
+				const file = 'const foo = 1;\n//# sourceMappingURL=foo.js.map\nconst bar = 2;';
+				expect(stripSourceMap(file)).toBe('const foo = 1;\nconst bar = 2;');
+			});
+		});
+	});
+});