frontend-app-api: make it possible to configure which extensions are forbidden

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/frontend-app-api/src/graph/createAppGraph.ts

@@ -40,7 +40,9 @@ export function createAppGraph(options: CreateAppGraphOptions): AppGraph {
       features: options.features,
       builtinExtensions: options.builtinExtensions,
       parameters: readAppExtensionsConfig(options.config),
+      forbidden: new Set(['core']),
     }),
+    'core',
   );
   instantiateAppNodeTree(appGraph.root);
   return appGraph;

packages/frontend-app-api/src/graph/resolveAppNodeSpecs.test.ts

@@ -234,4 +234,45 @@ describe('resolveAppNodeSpecs', () => {
 
     expect(result.map(r => r.extension.id)).toEqual(['b', 'c', 'a']);
   });
+
+  it('throws an error when a forbidden extension is overridden by a plugin', () => {
+    expect(() =>
+      resolveAppNodeSpecs({
+        features: [
+          createPlugin({ id: 'test', extensions: [makeExt('forbidden')] }),
+        ],
+        builtinExtensions: [],
+        parameters: [],
+        forbidden: new Set(['forbidden']),
+      }),
+    ).toThrow(
+      "It is forbidden to override the following extension(s): 'forbidden', which is done by the following plugin(s): 'test'",
+    );
+  });
+
+  it('throws an error when a forbidden extension is overridden by overrides', () => {
+    expect(() =>
+      resolveAppNodeSpecs({
+        features: [
+          createExtensionOverrides({ extensions: [makeExt('forbidden')] }),
+        ],
+        builtinExtensions: [],
+        parameters: [],
+        forbidden: new Set(['forbidden']),
+      }),
+    ).toThrow(
+      "It is forbidden to override the following extension(s): 'forbidden', which is done by one or more extension overrides",
+    );
+  });
+
+  it('throws an error when a forbidden extension is parametrized', () => {
+    expect(() =>
+      resolveAppNodeSpecs({
+        features: [],
+        builtinExtensions: [],
+        parameters: [{ id: 'forbidden', disabled: false }],
+        forbidden: new Set(['forbidden']),
+      }),
+    ).toThrow("Configuration of the 'forbidden' extension is forbidden");
+  });
 });

packages/frontend-app-api/src/graph/resolveAppNodeSpecs.ts

@@ -29,8 +29,9 @@ export function resolveAppNodeSpecs(options: {
   features: (BackstagePlugin | ExtensionOverrides)[];
   builtinExtensions: Extension<unknown>[];
   parameters: Array<ExtensionParameters>;
+  forbidden?: Set<string>;
 }): AppNodeSpec[] {
-  const { builtinExtensions, parameters } = options;
+  const { builtinExtensions, parameters, forbidden = new Set() } = options;
 
   const plugins = options.features.filter(
     (f): f is BackstagePlugin => f.$$type === '@backstage/BackstagePlugin',
@@ -48,20 +49,21 @@ export function resolveAppNodeSpecs(options: {
   );
 
   // Prevent core override
-  if (pluginExtensions.some(({ id }) => id === 'core')) {
-    const pluginIds = pluginExtensions
-      .filter(({ id }) => id === 'core')
-      .map(({ source }) => source.id);
+  if (pluginExtensions.some(({ id }) => forbidden.has(id))) {
+    const pluginsStr = pluginExtensions
+      .filter(({ id }) => forbidden.has(id))
+      .map(({ source }) => `'${source.id}'`)
+      .join(', ');
+    const forbiddenStr = [...forbidden].map(id => `'${id}'`).join(', ');
     throw new Error(
-      `The following plugin(s) are overriding the 'core' extension which is forbidden: ${pluginIds.join(
-        ',',
-      )}`,
+      `It is forbidden to override the following extension(s): ${forbiddenStr}, which is done by the following plugin(s): ${pluginsStr}`,
     );
   }
 
-  if (overrideExtensions.some(({ id }) => id === 'root')) {
+  if (overrideExtensions.some(({ id }) => forbidden.has(id))) {
+    const forbiddenStr = [...forbidden].map(id => `'${id}'`).join(', ');
     throw new Error(
-      `An extension override is overriding the 'root' extension which is forbidden`,
+      `It is forbidden to override the following extension(s): ${forbiddenStr}, which is done by one or more extension overrides`,
     );
   }
   const overrideExtensionIds = overrideExtensions.map(({ id }) => id);
@@ -164,6 +166,12 @@ export function resolveAppNodeSpecs(options: {
   for (const overrideParam of parameters) {
     const extensionId = overrideParam.id;
 
+    if (forbidden.has(extensionId)) {
+      throw new Error(
+        `Configuration of the '${extensionId}' extension is forbidden`,
+      );
+    }
+
     const existingIndex = configuredExtensions.findIndex(
       e => e.extension.id === extensionId,
     );