fix(perf): cache lengths/locals in more hot loops

lib/HookCodeFactory.js

@@ -14,7 +14,7 @@ class HookCodeFactory {
 	create(options) {
 		this.init(options);
 		let fn;
-		switch (this.options.type) {
+		switch (options.type) {
 			case "sync":
 				fn = new Function(
 					this.args(),
@@ -91,9 +91,10 @@ class HookCodeFactory {
 	 */
 	init(options) {
 		this.options = options;
-		// slice() avoids the iterator protocol overhead of [...arr].
-		// eslint-disable-next-line unicorn/prefer-spread
-		this._args = options.args.slice();
+		// `_args` is only read (length / join / [0]) - never mutated - so we
+		// can share the caller's array directly instead of paying for a copy
+		// on every compile.
+		this._args = options.args;
 		this._joinedArgs = undefined;
 	}
 
@@ -454,23 +455,23 @@ class HookCodeFactory {
 	}
 
 	args({ before, after } = {}) {
-		// Hot during code generation (called once per tap + per interceptor).
-		// Cache the common no-before/no-after result so we only join once.
-		if (before === undefined && after === undefined) {
-			let joined = this._joinedArgs;
-			if (joined === undefined) {
-				joined = this._args.length === 0 ? "" : this._args.join(", ");
-				this._joinedArgs = joined;
-			}
-			return joined;
+		// Hot during code generation. Join `_args` once and cache the result,
+		// then build the customized variants via string concat instead of
+		// allocating temporary `[before, ...allArgs]` / `[...allArgs, after]`
+		// arrays and re-joining.
+		let joined = this._joinedArgs;
+		if (joined === undefined) {
+			joined = this._args.length === 0 ? "" : this._args.join(", ");
+			this._joinedArgs = joined;
 		}
-		let allArgs = this._args;
-		if (before) allArgs = [before, ...allArgs];
-		if (after) allArgs = [...allArgs, after];
-		if (allArgs.length === 0) {
-			return "";
+		if (!before && !after) return joined;
+		if (joined.length === 0) {
+			if (before && after) return `${before}, ${after}`;
+			return before || after;
 		}
-		return allArgs.join(", ");
+		if (before && after) return `${before}, ${joined}, ${after}`;
+		if (before) return `${before}, ${joined}`;
+		return `${joined}, ${after}`;
 	}
 
 	getTapFn(idx) {