enhancement(schematics): include path in json parsing error message (#1048)

packages/schematics/src/utils/ast-utils.spec.ts

@@ -0,0 +1,37 @@
+import { readJsonInTree } from './ast-utils';
+import { SchematicTestRunner } from '@angular-devkit/schematics/testing';
+import { join } from 'path';
+import { Tree } from '@angular-devkit/schematics';
+import { serializeJson } from './fileutils';
+
+describe('readJsonInTree', () => {
+  let tree: Tree;
+
+  beforeEach(() => {
+    tree = Tree.empty();
+  });
+  it('should read JSON from the tree', () => {
+    tree.create(
+      'data.json',
+      serializeJson({
+        data: 'data'
+      })
+    );
+    expect(readJsonInTree(tree, 'data.json')).toEqual({
+      data: 'data'
+    });
+  });
+
+  it('should throw an error if the file does not exist', () => {
+    expect(() => readJsonInTree(tree, 'data.json')).toThrow(
+      'Cannot find data.json'
+    );
+  });
+
+  it('should throw an error if the file cannot be parsed', () => {
+    tree.create('data.json', `{ data: 'data'`);
+    expect(() => readJsonInTree(tree, 'data.json')).toThrow(
+      'Cannot parse data.json: Unexpected token d in JSON at position 2'
+    );
+  });
+});

packages/schematics/src/utils/ast-utils.ts

@@ -577,8 +577,12 @@ export function readJsonInTree<T = any>(host: Tree, path: string): T {
   if (!host.exists(path)) {
     throw new Error(`Cannot find ${path}`);
   }
-
-  return JSON.parse(stripJsonComments(host.read(path)!.toString('utf-8')));
+  const contents = host.read(path)!.toString('utf-8');
+  try {
+    return JSON.parse(contents);
+  } catch (e) {
+    throw new Error(`Cannot parse ${path}: ${e.message}`);
+  }
 }
 
 /**