refactor(@angular/build): optimize JavaScript transformer worker startup and sourcemap generation

packages/angular/build/src/tools/esbuild/javascript-transformer-worker.ts

@@ -7,7 +7,7 @@
  */
 
 import remapping, { type DecodedSourceMap, type EncodedSourceMap } from '@ampproject/remapping';
-import { type PluginItem, transformAsync } from '@babel/core';
+import type { PluginItem } from '@babel/core';
 import { createRequire } from 'node:module';
 import { workerData } from 'node:worker_threads';
 import Piscina from 'piscina';
@@ -42,6 +42,16 @@ const {
   jit = false,
 } = (workerData || {}) as Partial<JavaScriptTransformerOptions>;
 
+let babelLinkerDeps:
+  | Promise<
+      [
+        typeof import('@angular/compiler-cli/linker/babel'),
+        typeof import('@angular/compiler-cli'),
+        typeof import('@babel/core'),
+      ]
+    >
+  | undefined;
+
 const textDecoder = new TextDecoder();
 const textEncoder = new TextEncoder();
 
@@ -170,8 +180,13 @@ async function transformJavaScriptImpl(
   }
 
   if (shouldLink && useBabelLinker) {
-    const { createEs2015LinkerPlugin } = await import('@angular/compiler-cli/linker/babel');
-    const { ConsoleLogger, LogLevel } = await import('@angular/compiler-cli');
+    babelLinkerDeps ??= Promise.all([
+      import('@angular/compiler-cli/linker/babel'),
+      import('@angular/compiler-cli'),
+      import('@babel/core'),
+    ]);
+    const [{ createEs2015LinkerPlugin }, { ConsoleLogger, LogLevel }, { transformAsync }] =
+      await babelLinkerDeps;
 
     const result = await transformAsync(code, {
       filename,

packages/angular/build/src/tools/oxc/oxc-transform.ts

@@ -737,7 +737,7 @@ export function transform(filename: string, code: string, options: OxcTransformO
 
   let map: DecodedSourceMap | undefined;
   if (options.sourcemap) {
-    const rawMap = source.generateDecodedMap({ hires: true, source: filename });
+    const rawMap = source.generateDecodedMap({ hires: 'boundary', source: filename });
     map = { ...rawMap, version: 3 };
   }