feat(scaffolder): error handling, log propagation

Co-authored-by: Ben Lambert <ben@blam.sh>

plugins/scaffolder-backend/src/scaffolder/templater/cookiecutter.test.ts

@@ -16,8 +16,11 @@
 import { CookieCutter } from './cookiecutter';
 import fs from 'fs-extra';
 import os from 'os';
+import Stream, { PassThrough } from 'stream';
 
-const mockDocker = { run: jest.fn() };
+const mockDocker = {
+  run: jest.fn<any, any>(() => [{ Error: null, StatusCode: 0 }]),
+};
 jest.mock(
   'dockerode',
   () =>
@@ -32,7 +35,7 @@ describe('CookieCutter Templater', () => {
   const cookie = new CookieCutter();
 
   beforeEach(() => {
-    jest.resetAllMocks();
+    jest.clearAllMocks();
   });
 
   it('should write a cookiecutter.json file with the values from the entitiy', async () => {
@@ -85,8 +88,8 @@ describe('CookieCutter Templater', () => {
     // to @backstage/cookiecutter in docker hub.
     expect(mockDocker.run).toHaveBeenCalledWith(
       'backstage/cookiecutter',
-      ['cookiecutter', '--no-input', '-o', '/result', '/template', '--verbose'],
-      process.stdout,
+      ['cookiecutter', '--no-input', '-o', '/result', '/template'],
+      expect.any(Stream),
       expect.objectContaining({
         HostConfig: {
           Binds: expect.arrayContaining([
@@ -116,4 +119,63 @@ describe('CookieCutter Templater', () => {
 
     expect(path).toBe(`${realpath}/result`);
   });
+
+  it('throws a correct error if the templating fails in docker', async () => {
+    mockDocker.run.mockResolvedValueOnce([
+      {
+        Error: new Error('Something went wrong with docker'),
+        StatusCode: 0,
+      },
+    ]);
+
+    const tempdir = os.tmpdir();
+
+    const values = {
+      component_id: 'test',
+      description: 'description',
+    };
+
+    await expect(cookie.run({ directory: tempdir, values })).rejects.toThrow(
+      /Something went wrong with docker/,
+    );
+  });
+
+  it('uses the passed stream as a log stream', async () => {
+    const logStream = new PassThrough();
+    const tempdir = os.tmpdir();
+
+    const values = {
+      component_id: 'test',
+      description: 'description',
+    };
+
+    await cookie.run({ directory: tempdir, values, logStream });
+
+    expect(mockDocker.run).toHaveBeenCalledWith(
+      expect.any(String),
+      expect.any(Array),
+      logStream,
+      expect.any(Object),
+    );
+  });
+
+  it('throws a correct error if the container returns a non-zero exit code', async () => {
+    mockDocker.run.mockResolvedValueOnce([
+      {
+        Error: null,
+        StatusCode: 1,
+      },
+    ]);
+
+    const tempdir = os.tmpdir();
+
+    const values = {
+      component_id: 'test',
+      description: 'description',
+    };
+
+    await expect(cookie.run({ directory: tempdir, values })).rejects.toThrow(
+      /Docker container returned a non-zero exit code \(1\)/,
+    );
+  });
 });

plugins/scaffolder-backend/src/scaffolder/templater/cookiecutter.ts

@@ -18,7 +18,7 @@ import { TemplaterBase, TemplaterRunOptions } from '.';
 import fs from 'fs-extra';
 import Docker from 'dockerode';
 import { JsonValue } from '@backstage/config';
-
+import { PassThrough } from 'stream';
 export class CookieCutter implements TemplaterBase {
   private docker: Docker;
   constructor() {
@@ -51,10 +51,12 @@ export class CookieCutter implements TemplaterBase {
     const realTemplatePath = await fs.promises.realpath(options.directory);
     const outDir = `${realTemplatePath}/result`;
 
-    await this.docker.run(
+    const [
+      { Error: dockerError, StatusCode: containerStatusCode },
+    ] = await this.docker.run(
       'backstage/cookiecutter',
-      ['cookiecutter', '--no-input', '-o', '/result', '/template', '--verbose'],
-      process.stdout,
+      ['cookiecutter', '--no-input', '-o', '/result', '/template'],
+      options.logStream ?? new PassThrough(),
       {
         Volumes: { '/result': {}, '/template': {} },
         HostConfig: {
@@ -63,6 +65,18 @@ export class CookieCutter implements TemplaterBase {
       },
     );
 
+    if (dockerError) {
+      throw new Error(
+        `Docker failed to run with the following error message: ${dockerError}`,
+      );
+    }
+
+    if (containerStatusCode !== 0) {
+      throw new Error(
+        `Docker container returned a non-zero exit code (${containerStatusCode})`,
+      );
+    }
+
     return outDir;
   }
 }

plugins/scaffolder-backend/src/scaffolder/templater/index.ts

@@ -14,6 +14,8 @@
  * limitations under the License.
  */
 
+import type { Writable } from 'stream';
+
 export interface RequiredTemplateValues {
   component_id: string;
 }
@@ -21,6 +23,7 @@ export interface RequiredTemplateValues {
 export interface TemplaterRunOptions {
   directory: string;
   values: RequiredTemplateValues & object;
+  logStream?: Writable;
 }
 
 export abstract class TemplaterBase {

plugins/scaffolder-backend/src/service/router.ts

@@ -69,7 +69,7 @@ export async function createRouter(
     // Run the templater on the mock directory with values from the post body
     const templatedPath = await templater.run({
       directory: skeletonPath,
-      values: { component_id: 'test', description: "Something for now" },
+      values: { component_id: 'test' },
     });
 
     console.warn(templatedPath);