Merge pull request #12955 from webpack/perf/serialize

improve cache serialization performance by 30%

lib/serialization/ObjectMiddleware.js

@@ -408,16 +408,13 @@ class ObjectMiddleware extends SerializerMiddleware {
 		};
 		this.extendContext(ctx);
 		const process = item => {
-			// check if we can emit a reference
-			const ref = referenceable.get(item);
-
-			if (ref !== undefined) {
-				result.push(ESCAPE, ref - currentPos);
-
-				return;
-			}
-
 			if (Buffer.isBuffer(item)) {
+				// check if we can emit a reference
+				const ref = referenceable.get(item);
+				if (ref !== undefined) {
+					result.push(ESCAPE, ref - currentPos);
+					return;
+				}
 				const alreadyUsedBuffer = dedupeBuffer(item);
 				if (alreadyUsedBuffer !== item) {
 					const ref = referenceable.get(alreadyUsedBuffer);
@@ -431,7 +428,19 @@ class ObjectMiddleware extends SerializerMiddleware {
 				addReferenceable(item);
 
 				result.push(item);
-			} else if (typeof item === "object" && item !== null) {
+			} else if (item === ESCAPE) {
+				result.push(ESCAPE, ESCAPE_ESCAPE_VALUE);
+			} else if (
+				typeof item === "object"
+				// We don't have to check for null as ESCAPE is null and this has been checked before
+			) {
+				// check if we can emit a reference
+				const ref = referenceable.get(item);
+				if (ref !== undefined) {
+					result.push(ESCAPE, ref - currentPos);
+					return;
+				}
+
 				if (cycleStack.has(item)) {
 					throw new Error(`Circular references can't be serialized`);
 				}
@@ -464,6 +473,12 @@ class ObjectMiddleware extends SerializerMiddleware {
 			} else if (typeof item === "string") {
 				if (item.length > 1) {
 					// short strings are shorter when not emitting a reference (this saves 1 byte per empty string)
+					// check if we can emit a reference
+					const ref = referenceable.get(item);
+					if (ref !== undefined) {
+						result.push(ESCAPE, ref - currentPos);
+						return;
+					}
 					addReferenceable(item);
 				}
 
@@ -476,8 +491,6 @@ class ObjectMiddleware extends SerializerMiddleware {
 				}
 
 				result.push(item);
-			} else if (item === ESCAPE) {
-				result.push(ESCAPE, ESCAPE_ESCAPE_VALUE);
 			} else if (typeof item === "function") {
 				if (!SerializerMiddleware.isLazy(item))
 					throw new Error("Unexpected function " + item);