scaffolder-backend: add dry-run implementation

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

plugins/scaffolder-backend/src/scaffolder/dryrun/DecoratedActionsRegistry.ts

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2022 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { JsonObject } from '@backstage/types';
+import { TemplateAction, TemplateActionRegistry } from '../actions';
+
+/** @internal */
+export class DecoratedActionsRegistry extends TemplateActionRegistry {
+  constructor(
+    private readonly innerRegistry: TemplateActionRegistry,
+    extraActions: Array<TemplateAction<JsonObject>>,
+  ) {
+    super();
+    for (const action of extraActions) {
+      this.register(action);
+    }
+  }
+
+  get(actionId: string): TemplateAction<JsonObject> {
+    try {
+      return super.get(actionId);
+    } catch {
+      return this.innerRegistry.get(actionId);
+    }
+  }
+}

plugins/scaffolder-backend/src/scaffolder/dryrun/createDryRunner.ts

@@ -0,0 +1,143 @@
+/*
+ * Copyright 2022 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { ScmIntegrations } from '@backstage/integration';
+import { TaskSpec } from '@backstage/plugin-scaffolder-common';
+import { JsonObject } from '@backstage/types';
+import { v4 as uuid } from 'uuid';
+import { pathToFileURL } from 'url';
+import { Logger } from 'winston';
+import {
+  deserializeDirectoryContents,
+  SerializedFile,
+  serializeDirectoryContents,
+} from '../../lib/files';
+import { TemplateFilter } from '../../lib/templating';
+import { createTemplateAction, TemplateActionRegistry } from '../actions';
+import { NunjucksWorkflowRunner } from '../tasks/NunjucksWorkflowRunner';
+import { TaskSecrets } from '../tasks/types';
+import { DecoratedActionsRegistry } from './DecoratedActionsRegistry';
+import fs from 'fs-extra';
+import { resolveSafeChildPath } from '@backstage/backend-common';
+
+interface DryRunInput {
+  spec: TaskSpec;
+  secrets?: TaskSecrets;
+  content: SerializedFile[];
+}
+
+interface DryRunResult {
+  log: JsonObject[];
+  content: SerializedFile[];
+  output: JsonObject;
+}
+
+/** @internal */
+export type TemplateTesterCreateOptions = {
+  logger: Logger;
+  integrations: ScmIntegrations;
+  actionRegistry: TemplateActionRegistry;
+  workingDirectory: string;
+  additionalTemplateFilters?: Record<string, TemplateFilter>;
+};
+
+/**
+ * Executes a dry-run of the provided template.
+ *
+ * The provided content will be extracted into a temporary directory
+ * which is then use as the base for any relative file fetch paths.
+ *
+ * @internal
+ */
+export function createDryRunner(options: TemplateTesterCreateOptions) {
+  return async function dryRun(input: DryRunInput): Promise<DryRunResult> {
+    let contentPromise;
+
+    const workflowRunner = new NunjucksWorkflowRunner({
+      ...options,
+      actionRegistry: new DecoratedActionsRegistry(options.actionRegistry, [
+        createTemplateAction({
+          id: 'dry-run:extract',
+          supportsDryRun: true,
+          async handler(ctx) {
+            contentPromise = serializeDirectoryContents(ctx.workspacePath);
+            await contentPromise.catch(() => {});
+          },
+        }),
+      ]),
+    });
+
+    const dryRunId = uuid();
+    const log = new Array<JsonObject>();
+    const contentsPath = resolveSafeChildPath(
+      options.workingDirectory,
+      `dry-run-content-${dryRunId}`,
+    );
+
+    try {
+      await deserializeDirectoryContents(contentsPath, input.content);
+
+      const result = await workflowRunner.execute({
+        spec: {
+          ...input.spec,
+          steps: [
+            ...input.spec.steps,
+            {
+              id: dryRunId,
+              name: 'dry-run:extract',
+              action: 'dry-run:extract',
+            },
+          ],
+          templateInfo: {
+            entityRef: 'template:default/dry-run',
+            baseUrl: pathToFileURL(
+              resolveSafeChildPath(contentsPath, 'template.yaml'),
+            ).toString(),
+          },
+        },
+        secrets: input.secrets,
+        done: false,
+        isDryRun: true,
+        getWorkspaceName: async () => `dry-run-${dryRunId}`,
+        async emitLog(message: string, logMetadata?: JsonObject) {
+          if (logMetadata?.stepId === dryRunId) {
+            return;
+          }
+          log.push({
+            ...logMetadata,
+            message,
+          });
+        },
+        async complete() {
+          throw new Error('Not implemented');
+        },
+      });
+
+      if (!contentPromise) {
+        throw new Error('Content extraction step was skipped');
+      }
+      const content = await contentPromise;
+
+      return {
+        log,
+        content,
+        output: result.output,
+      };
+    } finally {
+      await fs.remove(contentsPath);
+    }
+  };
+}

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

@@ -0,0 +1,17 @@
+/*
+ * Copyright 2022 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export { createDryRunner } from './createDryRunner';