From 124ad10b8ccc05c716e727fff2eacf83b320520d Mon Sep 17 00:00:00 2001
From: dpiercey <dpiercey@ebay.com>
Date: Sun, 24 Nov 2024 14:25:59 -0700
Subject: [PATCH] perf: improve script parsing

---
 .changeset/bright-moons-push.md               |  5 ++++
 .../src/extractors/script/index.ts            |  2 +-
 .../extractors/script/util/script-parser.ts   | 30 ++++++++++++-------
 3 files changed, 25 insertions(+), 12 deletions(-)
 create mode 100644 .changeset/bright-moons-push.md

diff --git a/.changeset/bright-moons-push.md b/.changeset/bright-moons-push.md
new file mode 100644
index 00000000..521703d6
--- /dev/null
+++ b/.changeset/bright-moons-push.md
@@ -0,0 +1,5 @@
+---
+"@marko/language-tools": patch
+---
+
+Improve script parsing performance.
diff --git a/packages/language-tools/src/extractors/script/index.ts b/packages/language-tools/src/extractors/script/index.ts
index 8b24af72..c35b4788 100644
--- a/packages/language-tools/src/extractors/script/index.ts
+++ b/packages/language-tools/src/extractors/script/index.ts
@@ -119,7 +119,7 @@ class ScriptExtractor {
     this.#ts = opts.ts;
     this.#runtimeTypes = opts.runtimeTypesCode;
     this.#extractor = new Extractor(parsed);
-    this.#scriptParser = new ScriptParser(parsed.filename, parsed.code);
+    this.#scriptParser = new ScriptParser(parsed);
     this.#read = parsed.read.bind(parsed);
     this.#mutationOffsets = crawlProgramScope(this.#parsed, this.#scriptParser);
     this.#writeProgram(parsed.program);
diff --git a/packages/language-tools/src/extractors/script/util/script-parser.ts b/packages/language-tools/src/extractors/script/util/script-parser.ts
index 874ee54c..266997b5 100644
--- a/packages/language-tools/src/extractors/script/util/script-parser.ts
+++ b/packages/language-tools/src/extractors/script/util/script-parser.ts
@@ -5,6 +5,8 @@ import {
 } from "@babel/parser";
 import type * as t from "@babel/types";
 
+import type { Parsed } from "../../../parser";
+
 const plugins: ParserOptions["plugins"] = [
   "exportDefaultFrom",
   "importAssertions",
@@ -12,17 +14,19 @@ const plugins: ParserOptions["plugins"] = [
 ];
 
 export class ScriptParser {
-  #sourceFileName: string;
-  #whitespace: string;
-  constructor(sourceFileName: string, code: string) {
-    this.#sourceFileName = sourceFileName;
-    this.#whitespace = code.replace(/[^\s]/g, " "); // used to ensure that babel provides the correct source locations.
+  #parsed: Parsed;
+  constructor(parsed: Parsed) {
+    this.#parsed = parsed;
   }
 
-  statementAt<T = t.Statement[]>(offset: number, src: string) {
+  statementAt<T = t.Statement[]>(startIndex: number, src: string) {
+    const pos = this.#parsed.positionAt(startIndex);
     try {
-      return parseStatement(this.#whitespace.slice(0, offset) + src, {
+      return parseStatement(src, {
         plugins,
+        startIndex,
+        startLine: pos.line + 1,
+        startColumn: pos.character,
         strictMode: true,
         errorRecovery: true,
         sourceType: "module",
@@ -30,17 +34,21 @@ export class ScriptParser {
         allowSuperOutsideMethod: true,
         allowAwaitOutsideFunction: true,
         allowReturnOutsideFunction: true,
-        sourceFilename: this.#sourceFileName,
+        sourceFilename: this.#parsed.filename,
       }).program.body as unknown as T extends unknown[] ? T : Readonly<[T]>;
     } catch {
       return [];
     }
   }
 
-  expressionAt<T = t.Expression>(offset: number, src: string) {
+  expressionAt<T = t.Expression>(startIndex: number, src: string) {
+    const pos = this.#parsed.positionAt(startIndex);
     try {
-      return parseExpression(this.#whitespace.slice(0, offset) + src, {
+      return parseExpression(src, {
         plugins,
+        startIndex,
+        startLine: pos.line + 1,
+        startColumn: pos.character,
         strictMode: true,
         errorRecovery: true,
         sourceType: "module",
@@ -48,7 +56,7 @@ export class ScriptParser {
         allowSuperOutsideMethod: true,
         allowAwaitOutsideFunction: true,
         allowReturnOutsideFunction: true,
-        sourceFilename: this.#sourceFileName,
+        sourceFilename: this.#parsed.filename,
       }) as unknown as T;
     } catch {
       return;