fix(@angular-devkit/core): provide actionable error when a workspace project has missing root property

The `root` property is required in a workspace project. Now we issue an actionable error message when this is missing.

Closes: #21310

Author: alan-agius4

packages/angular_devkit/core/src/workspace/json/reader.ts

@@ -167,6 +167,12 @@ function parseProject(
   }
 
   const projectNodeValue = getNodeValue(projectNode);
+  if (!('root' in projectNodeValue)) {
+    context.error(
+      `Project "${projectName}" is missing a required property "root".`,
+      projectNodeValue,
+    );
+  }
 
   for (const [name, value] of Object.entries<JsonValue>(projectNodeValue)) {
     switch (name) {

packages/angular_devkit/core/src/workspace/json/reader_spec.ts

@@ -137,6 +137,21 @@ describe('readJsonWorkpace Parsing', () => {
       /version specifier not found/,
     );
   });
+
+  it('errors on missing root property in a project', async () => {
+    const host = createTestHost(stripIndent`
+      {
+        "version": 1,
+        "projects": {
+          "foo": {}
+        }
+      }
+    `);
+
+    await expectAsync(readJsonWorkspace('', host)).toBeRejectedWithError(
+      /Project "foo" is missing a required property "root"/,
+    );
+  });
 });
 
 describe('JSON WorkspaceDefinition Tracks Workspace Changes', () => {