fix(@angular-devkit/build-angular): support dev server proxy pathRewrite field in Vite-based server

The development server proxy configuration file for Webpack supports a `pathRewrite` field that is
not directly supported by the underlying Vite development server when using the application or esbuild-
browser builders. To provide equivalent support, especially for JSON file-based proxy configurations,
the `pathRewrite` field is now converted internally to a proxy `rewrite` function.

Author: clydin

packages/angular_devkit/build_angular/src/builders/dev-server/load-proxy-config.ts

@@ -95,9 +95,9 @@ export async function loadProxyConfiguration(
  * @param proxy A proxy configuration object.
  */
 function normalizeProxyConfiguration(
-  proxy: Record<string, unknown> | object[],
-): Record<string, unknown> {
-  let normalizedProxy: Record<string, unknown> | undefined;
+  proxy: Record<string, object> | object[],
+): Record<string, object> {
+  let normalizedProxy: Record<string, object> | undefined;
 
   if (Array.isArray(proxy)) {
     // Construct an object-form proxy configuration from the array
@@ -135,9 +135,44 @@ function normalizeProxyConfiguration(
     }
   }
 
+  // Replace `pathRewrite` field with a `rewrite` function
+  for (const proxyEntry of Object.values(normalizedProxy)) {
+    if (
+      'pathRewrite' in proxyEntry &&
+      proxyEntry.pathRewrite &&
+      typeof proxyEntry.pathRewrite === 'object'
+    ) {
+      // Preprocess path rewrite entries
+      const pathRewriteEntries: [RegExp, string][] = [];
+      for (const [pattern, value] of Object.entries(
+        proxyEntry.pathRewrite as Record<string, string>,
+      )) {
+        pathRewriteEntries.push([new RegExp(pattern), value]);
+      }
+
+      (proxyEntry as Record<string, unknown>).rewrite = pathRewriter.bind(
+        undefined,
+        pathRewriteEntries,
+      );
+
+      delete proxyEntry.pathRewrite;
+    }
+  }
+
   return normalizedProxy;
 }
 
+function pathRewriter(pathRewriteEntries: [RegExp, string][], path: string): string {
+  for (const [pattern, value] of pathRewriteEntries) {
+    const updated = path.replace(pattern, value);
+    if (path !== updated) {
+      return updated;
+    }
+  }
+
+  return path;
+}
+
 /**
  * Calculates the line and column for an error offset in the content of a JSON file.
  * @param location The offset error location from the beginning of the content.