scaffolder-backend: fixes for mock-fs interfering with nunjucks loading

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

plugins/scaffolder-backend/src/scaffolder/actions/builtin/fetch/template.test.ts

@@ -33,6 +33,17 @@ jest.mock('./helpers', () => ({
   fetchContents: jest.fn(),
 }));
 
+const realFiles = Object.fromEntries(
+  [
+    require.resolve('vm2/lib/fixasync'),
+    resolvePackagePath(
+      '@backstage/plugin-scaffolder-backend',
+      'assets',
+      'nunjucks.js.txt',
+    ),
+  ].map(k => [k, mockFs.load(k)]),
+);
+
 const aBinaryFile = fs.readFileSync(
   resolvePackagePath(
     '@backstage/plugin-scaffolder-backend',
@@ -76,7 +87,9 @@ describe('fetch:template', () => {
   });
 
   beforeEach(() => {
-    mockFs();
+    mockFs({
+      ...realFiles,
+    });
 
     action = createFetchTemplateAction({
       reader: Symbol('UrlReader') as unknown as UrlReader,
@@ -150,6 +163,7 @@ describe('fetch:template', () => {
 
         mockFetchContents.mockImplementation(({ outputPath }) => {
           mockFs({
+            ...realFiles,
             [outputPath]: {
               'an-executable.sh': mockFs.file({
                 content: '#!/usr/bin/env bash',
@@ -259,6 +273,7 @@ describe('fetch:template', () => {
 
         mockFetchContents.mockImplementation(({ outputPath }) => {
           mockFs({
+            ...realFiles,
             [outputPath]: {
               processed: {
                 'templated-content-${{ values.name }}.txt':
@@ -312,6 +327,7 @@ describe('fetch:template', () => {
 
       mockFetchContents.mockImplementation(({ outputPath }) => {
         mockFs({
+          ...realFiles,
           [outputPath]: {
             '{{ cookiecutter.name }}.txt': 'static content',
             subdir: {
@@ -366,6 +382,7 @@ describe('fetch:template', () => {
 
       mockFetchContents.mockImplementation(({ outputPath }) => {
         mockFs({
+          ...realFiles,
           [outputPath]: {
             'empty-dir-${{ values.count }}': {},
             'static.txt': 'static content',
@@ -447,6 +464,7 @@ describe('fetch:template', () => {
 
       mockFetchContents.mockImplementation(({ outputPath }) => {
         mockFs({
+          ...realFiles,
           [outputPath]: {
             '${{ values.name }}.njk': '${{ values.name }}: ${{ values.count }}',
             '${{ values.name }}.txt.jinja2':

plugins/scaffolder-backend/src/scaffolder/tasks/NunjucksWorkflowRunner.test.ts

@@ -17,13 +17,24 @@
 import mockFs from 'mock-fs';
 import * as winston from 'winston';
 
-import { getVoidLogger } from '@backstage/backend-common';
+import { getVoidLogger, resolvePackagePath } from '@backstage/backend-common';
 import { NunjucksWorkflowRunner } from './NunjucksWorkflowRunner';
 import { TemplateActionRegistry } from '../actions';
 import { ScmIntegrations } from '@backstage/integration';
 import { ConfigReader } from '@backstage/config';
 import { TaskContext, TaskSpec } from './types';
 
+const realFiles = Object.fromEntries(
+  [
+    require.resolve('vm2/lib/fixasync'),
+    resolvePackagePath(
+      '@backstage/plugin-scaffolder-backend',
+      'assets',
+      'nunjucks.js.txt',
+    ),
+  ].map(k => [k, mockFs.load(k)]),
+);
+
 describe('DefaultWorkflowRunner', () => {
   const logger = getVoidLogger();
   let actionRegistry = new TemplateActionRegistry();
@@ -50,6 +61,7 @@ describe('DefaultWorkflowRunner', () => {
     winston.format.simple(); // put logform the require cache before mocking fs
     mockFs({
       '/tmp': mockFs.directory(),
+      ...realFiles,
     });
 
     jest.resetAllMocks();

plugins/scaffolder-backend/src/scaffolder/tasks/NunjucksWorkflowRunner.ts

@@ -26,6 +26,7 @@ import {
 import * as winston from 'winston';
 import fs from 'fs-extra';
 import path from 'path';
+import nunjucks from 'nunjucks';
 import { JsonObject, JsonValue } from '@backstage/types';
 import { InputError } from '@backstage/errors';
 import { PassThrough } from 'stream';
@@ -102,7 +103,17 @@ export class NunjucksWorkflowRunner implements WorkflowRunner {
   }
 
   private isSingleTemplateString(input: string) {
-    const { parser, nodes } = require('nunjucks');
+    const { parser, nodes } = nunjucks as unknown as {
+      parser: {
+        parse(
+          template: string,
+          ctx: object,
+          options: nunjucks.ConfigureOptions,
+        ): { children: { children?: unknown[] }[] };
+      };
+      nodes: { TemplateData: Function };
+    };
+
     const parsed = parser.parse(
       input,
       {},