perf(@schematics/angular): optimize AST traversal utilities

Improves the performance of AST utility functions by reducing redundant work and memory allocations.

- The `findNodes` function is now memoized with a `WeakMap`-based cache. This prevents repeated traversals of the entire source file AST when searching for nodes of the same kind, which is a common pattern.
- The `getSourceNodes` function has been refactored to use a single array instead of two, reducing memory overhead and avoiding costly `shift()` operations.

Author: clydin

packages/schematics/angular/utility/ast-utils.ts

@@ -90,6 +90,11 @@ export function insertImport(
   );
 }
 
+const findNodesCache = new WeakMap<
+  ts.SourceFile,
+  Map<ts.SyntaxKind | ((node: ts.Node) => boolean), ts.Node[]>
+>();
+
 /**
  * Find all nodes from the AST in the subtree of node of SyntaxKind kind.
  * @param node
@@ -137,6 +142,14 @@ export function findNodes<T extends ts.Node>(
       ? kindOrGuard
       : (node: ts.Node): node is T => node.kind === kindOrGuard;
 
+  // Caching is only supported for the entire file
+  if (ts.isSourceFile(node)) {
+    const sourceFileCache = findNodesCache.get(node);
+    if (sourceFileCache?.has(kindOrGuard)) {
+      return sourceFileCache.get(kindOrGuard) as T[];
+    }
+  }
+
   const arr: T[] = [];
   if (test(node)) {
     arr.push(node);
@@ -157,6 +170,15 @@ export function findNodes<T extends ts.Node>(
     }
   }
 
+  if (ts.isSourceFile(node)) {
+    let sourceFileCache = findNodesCache.get(node);
+    if (!sourceFileCache) {
+      sourceFileCache = new Map();
+      findNodesCache.set(node, sourceFileCache);
+    }
+    sourceFileCache.set(kindOrGuard, arr);
+  }
+
   return arr;
 }
 
@@ -167,20 +189,14 @@ export function findNodes<T extends ts.Node>(
  */
 export function getSourceNodes(sourceFile: ts.SourceFile): ts.Node[] {
   const nodes: ts.Node[] = [sourceFile];
-  const result: ts.Node[] = [];
-
-  while (nodes.length > 0) {
-    const node = nodes.shift();
 
-    if (node) {
-      result.push(node);
-      if (node.getChildCount(sourceFile) >= 0) {
-        nodes.unshift(...node.getChildren());
-      }
-    }
+  // NOTE: nodes.length changes inside of the loop but we only append to the end
+  for (let i = 0; i < nodes.length; i++) {
+    const node = nodes[i];
+    nodes.push(...node.getChildren(sourceFile));
   }
 
-  return result;
+  return nodes;
 }
 
 export function findNode(node: ts.Node, kind: ts.SyntaxKind, text: string): ts.Node | null {