feat(api): redirect on error if request ACCEPTs html (#56445)

api/src/plugins/error-handling.test.ts

@@ -0,0 +1,83 @@
+import Fastify, { type FastifyInstance } from 'fastify';
+import accepts from '@fastify/accepts';
+
+import errorHandling from './error-handling';
+import redirectWithMessage, { formatMessage } from './redirect-with-message';
+
+describe('errorHandling', () => {
+  let fastify: FastifyInstance;
+
+  beforeEach(async () => {
+    fastify = Fastify();
+    await fastify.register(redirectWithMessage);
+    await fastify.register(accepts);
+    await fastify.register(errorHandling);
+
+    fastify.get('/test', async (_req, _reply) => {
+      throw new Error('a very bad thing happened');
+      return { ok: true };
+    });
+  });
+
+  afterEach(async () => {
+    await fastify.close();
+  });
+
+  it('should redirect to the referer if the request does not Accept json', async () => {
+    const res = await fastify.inject({
+      method: 'GET',
+      url: '/test',
+      headers: {
+        referer: 'https://www.freecodecamp.org/anything',
+        accept: 'text/plain'
+      }
+    });
+
+    expect(res.headers['location']).toEqual(
+      'https://www.freecodecamp.org/anything?' +
+        formatMessage({
+          type: 'danger',
+          content: 'flash.generic-error'
+        })
+    );
+    expect(res.statusCode).toEqual(302);
+  });
+
+  it('should return a json response if the request does Accept json', async () => {
+    const res = await fastify.inject({
+      method: 'GET',
+      url: '/test',
+      headers: {
+        referer: 'https://www.freecodecamp.org/anything',
+        accept: 'application/json,text/plain'
+      }
+    });
+
+    expect(res.json()).toEqual({
+      message: 'flash.generic-error',
+      type: 'danger'
+    });
+    expect(res.statusCode).toEqual(500);
+  });
+
+  it('should redirect if the request prefers text/html to json', async () => {
+    const res = await fastify.inject({
+      method: 'GET',
+      url: '/test',
+      headers: {
+        referer: 'https://www.freecodecamp.org/anything',
+        // this does accept json, (via the */*), but prefers text/html
+        accept: 'text/html,*/*'
+      }
+    });
+
+    expect(res.headers['location']).toEqual(
+      'https://www.freecodecamp.org/anything?' +
+        formatMessage({
+          type: 'danger',
+          content: 'flash.generic-error'
+        })
+    );
+    expect(res.statusCode).toEqual(302);
+  });
+});