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refactor(@angular/build): optimize removeSourceMappingURL with pre-check and range slicing #33780

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Merged
alan-agius4 merged 1 commit into from
Aug 6, 2026
+36 −34
Merged

refactor(@angular/build): optimize removeSourceMappingURL with pre-check and range slicing #33780

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60 changes: 26 additions & 34 deletions packages/angular/build/src/utils/source-map.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,12 @@ import { fileURLToPath } from 'node:url';
* @returns The code with top-level sourcemap comments removed.
*/
export function removeSourceMappingURL(code: string): string {
if (!code.includes('//# sourceMappingURL=')) {
return code;
}

const result: string[] = [];
let lastCopiedIndex = 0;
let i = 0;
const len = code.length;

Expand All @@ -30,7 +35,6 @@ export function removeSourceMappingURL(code: string): string {
let currentState:
'normal' | 'string_double' | 'string_single' | 'template' | 'comment_block' | 'comment_line' =
'normal';
let isStrippingComment = false;

while (i < len) {
const char = code[i];
Expand All @@ -39,20 +43,19 @@ export function removeSourceMappingURL(code: string): string {
if (currentState === 'normal') {
if (char === '/' && nextChar === '*') {
currentState = 'comment_block';
result.push('/*');
i += 2;
continue;
}
if (char === '/' && nextChar === '/') {
// Detect if the comment is escaped (e.g. inside a regex literal like `/\/\/#/`).
let isEscaped = false;
let prevIdx = result.length - 1;
while (prevIdx >= 0 && /\s/.test(result[prevIdx])) {
let prevIdx = i - 1;
while (prevIdx >= 0 && /\s/.test(code[prevIdx])) {
prevIdx--;
}
if (prevIdx >= 0 && result[prevIdx] === '\\') {
if (prevIdx >= 0 && code[prevIdx] === '\\') {
let bsCount = 0;
while (prevIdx >= 0 && result[prevIdx] === '\\') {
while (prevIdx >= 0 && code[prevIdx] === '\\') {
bsCount++;
prevIdx--;
}
Expand All @@ -62,34 +65,35 @@ export function removeSourceMappingURL(code: string): string {
}

if (!isEscaped && code.startsWith('//# sourceMappingURL=', i)) {
currentState = 'comment_line';
isStrippingComment = true;
i += 21; // Skip the '//# sourceMappingURL=' prefix
if (i > lastCopiedIndex) {
result.push(code.slice(lastCopiedIndex, i));
}
// Skip the rest of the comment line up to the newline
i += 21;
while (i < len && code[i] !== '\n' && code[i] !== '\r') {
i++;
}
lastCopiedIndex = i;
continue;
} else {
currentState = 'comment_line';
isStrippingComment = false;
result.push('//');
i += 2;
continue;
}
}
if (char === '"') {
currentState = 'string_double';
result.push('"');
i++;
continue;
}
if (char === "'") {
currentState = 'string_single';
result.push("'");
i++;
continue;
}
if (char === '`') {
currentState = 'template';
stack.push({ type: 'template', braceDepth: 0 });
result.push('`');
i++;
continue;
}
Expand All @@ -98,7 +102,6 @@ export function removeSourceMappingURL(code: string): string {
if (top) {
top.braceDepth++;
}
result.push('{');
i++;
continue;
}
Expand All @@ -110,84 +113,73 @@ export function removeSourceMappingURL(code: string): string {
// Exiting a template literal interpolation ${ ... }
stack.pop();
currentState = 'template';
result.push('}');
i++;
continue;
}
}
result.push('}');
i++;
continue;
}

result.push(char);
i++;
} else if (currentState === 'string_double') {
if (char === '\\') {
result.push(char, nextChar || '');
i += 2;
continue;
}
if (char === '"') {
currentState = 'normal';
}
result.push(char);
i++;
} else if (currentState === 'string_single') {
if (char === '\\') {
result.push(char, nextChar || '');
i += 2;
continue;
}
if (char === "'") {
currentState = 'normal';
}
result.push(char);
i++;
} else if (currentState === 'template') {
if (char === '\\') {
result.push(char, nextChar || '');
i += 2;
continue;
}
if (char === '$' && nextChar === '{') {
// Entering template literal interpolation context
currentState = 'normal';
stack.push({ type: 'template', braceDepth: 0 });
result.push('${');
i += 2;
continue;
}
if (char === '`') {
stack.pop();
currentState = 'normal';
}
result.push(char);
i++;
} else if (currentState === 'comment_block') {
if (char === '*' && nextChar === '/') {
currentState = 'normal';
result.push('*/');
i += 2;
continue;
}
result.push(char);
i++;
} else if (currentState === 'comment_line') {
if (char === '\n' || char === '\r') {
currentState = 'normal';
isStrippingComment = false;
result.push(char);
i++;
continue;
}
if (!isStrippingComment) {
result.push(char);
}
i++;
}
}

if (lastCopiedIndex === 0) {
return code;
}

if (lastCopiedIndex < len) {
result.push(code.slice(lastCopiedIndex));
}

return result.join('');
}

Expand Down
10 changes: 10 additions & 0 deletions packages/angular/build/src/utils/source-map_spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -87,4 +87,14 @@ describe('removeSourceMappingURL', () => {
const code = '// # sourceMappingURL=main.js.map\n//# sourceMappingURL=main.js.map';
expect(removeSourceMappingURL(code)).toBe('// # sourceMappingURL=main.js.map\n');
});

it('should return the exact input string when no sourcemap comment is present', () => {
const code = 'const x = 1;\nconsole.log(x);';
expect(removeSourceMappingURL(code)).toBe(code);
});

it('should handle sourcemap comments with CRLF newlines', () => {
const code = 'console.log("hello");\r\n//# sourceMappingURL=main.js.map\r\nconst next = 2;';
expect(removeSourceMappingURL(code)).toBe('console.log("hello");\r\n\r\nconst next = 2;');
});
});