Address code review comments

lib/RawSource.js

@@ -20,14 +20,16 @@ class RawSource extends Source {
 			throw new TypeError("argument 'value' must be either string or Buffer");
 		}
 		this._valueIsBuffer = !convertToString && isBuffer;
+		const internedString =
+			typeof value === "string" ? internString(value) : undefined;
 		this._value =
 			convertToString && isBuffer
 				? undefined
 				: typeof value === "string"
-				? internString(value)
+				? internedString
 				: value;
 		this._valueAsBuffer = isBuffer ? value : undefined;
-		this._valueAsString = isBuffer ? undefined : internString(value);
+		this._valueAsString = isBuffer ? undefined : internedString;
 	}
 
 	isBuffer() {
@@ -36,9 +38,9 @@ class RawSource extends Source {
 
 	source() {
 		if (this._value === undefined) {
-			const value = internString(this._valueAsBuffer.toString("utf-8"));
+			const value = this._valueAsBuffer.toString("utf-8");
 			if (isDualStringBufferCachingEnabled()) {
-				this._value = value;
+				this._value = internString(value);
 			}
 			return value;
 		}
@@ -68,17 +70,12 @@ class RawSource extends Source {
 	 * @returns {void}
 	 */
 	streamChunks(options, onChunk, onSource, onName) {
-		if (this._value === undefined && isDualStringBufferCachingEnabled()) {
-			this._value = Buffer.from(this._valueAsBuffer, "utf-8");
-		}
 		let strValue = this._valueAsString;
 		if (strValue === undefined) {
-			strValue =
-				typeof this._value === "string"
-					? this._value
-					: internString(this._value.toString("utf-8"));
+			const value = this.source();
+			strValue = typeof value === "string" ? value : value.toString("utf-8");
 			if (isDualStringBufferCachingEnabled()) {
-				this._valueAsString = strValue;
+				this._valueAsString = internString(strValue);
 			}
 		}
 		return streamChunksOfRawSource(

lib/helpers/stringBufferUtils.js

@@ -54,7 +54,12 @@ const interningStringMap = new Map();
  * of the same value if it has already been interned.
  */
 function internString(str) {
-	if (!isStringInterningEnabled() || !str || typeof str !== "string") {
+	if (
+		!isStringInterningEnabled() ||
+		!str ||
+		str.length < 128 ||
+		typeof str !== "string"
+	) {
 		return str;
 	}
 	let internedString = interningStringMap.get(str);