perf: defer _cachedSize allocation to first size() call

claude · claude · commit c5795b88d49a · 2026-04-22T17:20:39.000Z
The constructors of RawSource, OriginalSource and SourceMapSource preallocated `this._cachedSize = undefined` so that size() has a stable hidden-class slot to write to. That made every construction pay for memoization machinery regardless of whether .size() was ever called, showing up on CodSpeed as a ~12% regression on `cached-source: new CachedSource()` and 5-13% on several `source-map-source: new (*)` benchmarks. The size() overrides already guard on `this._cachedSize !== undefined`, which correctly handles missing properties. Drop the eager assignment and let the field be created on the first size() call. This keeps the size()/streamChunks() improvements from PR #199 (e.g. ~8x on a one-shot `new SMS().size()`) while erasing the construction regression. https://claude.ai/code/session_01LZbaaPrnDTu6y7s4nK4cJz
diff --git a/lib/OriginalSource.js b/lib/OriginalSource.js
@@ -49,11 +49,6 @@ class OriginalSource extends Source {
 		 * @type {string}
 		 */
 		this._name = name;
-		/**
-		 * @private
-		 * @type {undefined | number}
-		 */
-		this._cachedSize = undefined;
 	}
 
 	getName() {
diff --git a/lib/RawSource.js b/lib/RawSource.js
@@ -60,11 +60,6 @@ class RawSource extends Source {
 		} else {
 			throw new TypeError("argument 'value' must be either string or Buffer");
 		}
-		/**
-		 * @private
-		 * @type {undefined | number}
-		 */
-		this._cachedSize = undefined;
 	}
 
 	isBuffer() {
diff --git a/lib/SourceMapSource.js b/lib/SourceMapSource.js
@@ -113,11 +113,6 @@ class SourceMapSource extends Source {
 			: undefined;
 
 		this._removeOriginalSource = removeOriginalSource;
-		/**
-		 * @private
-		 * @type {undefined | number}
-		 */
-		this._cachedSize = undefined;
 	}
 
 	/**

Original file line number	Diff line number	Diff line change
`@@ -60,11 +60,6 @@ class RawSource extends Source {`
`60`	`60`	`} else {`
`61`	`61`	`throw new TypeError("argument 'value' must be either string or Buffer");`
`62`	`62`	`}`
`63`		`- /**`
`64`		`- * @private`
`65`		`- * @type {undefined \| number}`
`66`		`- */`
`67`		`- this._cachedSize = undefined;`
`68`	`63`	`}`
`69`	`64`
`70`	`65`	`isBuffer() {`