store url as Buffer to avoid serialization warnings

makes deserialization cheaper

lib/RuntimeTemplate.js

@@ -1031,7 +1031,7 @@ class RuntimeTemplate {
 		const codeGen = codeGenerationResults.get(module, runtime);
 		const { data } = codeGen;
 		const url = data.get("url");
-		if (url) return url;
+		if (url) return url.toString();
 		const filename = data.get("filename");
 		return publicPath + filename;
 	}

lib/asset/AssetGenerator.js

@@ -215,7 +215,7 @@ class AssetGenerator extends Generator {
 						},${encodedContent}`;
 					}
 					const data = getData();
-					data.set("url", encodedSource);
+					data.set("url", Buffer.from(encodedSource));
 					return new RawSource(
 						`${RuntimeGlobals.module}.exports = ${JSON.stringify(
 							encodedSource

lib/asset/RawDataUrlModule.js

@@ -33,6 +33,7 @@ class RawDataUrlModule extends Module {
 	constructor(url, identifier, readableIdentifier) {
 		super("asset/raw-data-url", null);
 		this.url = url;
+		this.urlBuffer = url ? Buffer.from(url) : undefined;
 		this.identifierStr = identifier || this.url;
 		this.readableIdentifierStr = readableIdentifier || this.identifierStr;
 	}
@@ -56,6 +57,7 @@ class RawDataUrlModule extends Module {
 	 * @returns {number} the estimated size of the module (must be non-zero)
 	 */
 	size(type) {
+		if (this.url === undefined) this.url = this.urlBuffer.toString();
 		return Math.max(1, this.url.length);
 	}
 
@@ -97,13 +99,14 @@ class RawDataUrlModule extends Module {
 	 * @returns {CodeGenerationResult} result
 	 */
 	codeGeneration(context) {
+		if (this.url === undefined) this.url = this.urlBuffer.toString();
 		const sources = new Map();
 		sources.set(
 			"javascript",
 			new RawSource(`module.exports = ${JSON.stringify(this.url)};`)
 		);
 		const data = new Map();
-		data.set("url", this.url);
+		data.set("url", this.urlBuffer);
 		const runtimeRequirements = new Set();
 		runtimeRequirements.add(RuntimeGlobals.module);
 		return { sources, runtimeRequirements, data };
@@ -115,14 +118,14 @@ class RawDataUrlModule extends Module {
 	 * @returns {void}
 	 */
 	updateHash(hash, context) {
-		hash.update(this.url);
+		hash.update(this.urlBuffer);
 		super.updateHash(hash, context);
 	}
 
 	serialize(context) {
 		const { write } = context;
 
-		write(this.url);
+		write(this.urlBuffer);
 		write(this.identifierStr);
 		write(this.readableIdentifierStr);
 
@@ -132,7 +135,7 @@ class RawDataUrlModule extends Module {
 	deserialize(context) {
 		const { read } = context;
 
-		this.url = read();
+		this.urlBuffer = read();
 		this.identifierStr = read();
 		this.readableIdentifierStr = read();