allow file deletion in pull requests

Signed-off-by: Phred <fearphage@gmail.com>

.changeset/social-insects-cheat.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-scaffolder-backend-module-github': patch
+---
+
+Added support for deleting files

plugins/scaffolder-backend-module-github/src/actions/githubPullRequest.test.ts

@@ -27,6 +27,7 @@ import fs from 'fs-extra';
 import { createPublishGithubPullRequestAction } from './githubPullRequest';
 import { createMockDirectory } from '@backstage/backend-test-utils';
 import { createMockActionContext } from '@backstage/plugin-scaffolder-node-test-utils';
+import { DELETE_FILE } from 'octokit-plugin-create-pull-request';
 
 type GithubPullRequestActionInput = ReturnType<
   typeof createPublishGithubPullRequestAction
@@ -46,12 +47,12 @@ describe('createPublishGithubPullRequestAction', () => {
   let config: Config;
   let integrations: ScmIntegrations;
 
+  const deletionMarker =
+    'if-you-find-a-file-whose-contents-matches-this-delete-it';
   const mockDir = createMockDirectory();
   const workspacePath = mockDir.resolve('workspace');
 
   beforeEach(() => {
-    mockDir.clear();
-
     config = new ConfigReader({});
     integrations = ScmIntegrations.fromConfig(config);
     fakeClient = {
@@ -92,6 +93,7 @@ describe('createPublishGithubPullRequestAction', () => {
   });
 
   afterEach(() => {
+    mockDir.clear();
     jest.resetAllMocks();
   });
 
@@ -304,6 +306,103 @@ describe('createPublishGithubPullRequestAction', () => {
     });
   });
 
+  describe('with deletionMarker', () => {
+    let input: GithubPullRequestActionInput;
+    let ctx: ActionContext<GithubPullRequestActionInput, any, any>;
+
+    beforeEach(() => {
+      input = {
+        deletionMarker,
+        repoUrl: 'github.com?owner=myorg&repo=myrepo',
+        title: 'Create my new app',
+        branchName: 'new-app',
+        description: 'This PR is really good',
+      };
+
+      mockDir.setContent({
+        [workspacePath]: {
+          'catpants.md': 'cat + pants',
+          'foobar.txt': 'Hello there!',
+        },
+      });
+
+      ctx = createMockActionContext({ input, workspacePath });
+    });
+
+    it('should create a pull request when no files match the marker', async () => {
+      await instance.handler(ctx);
+
+      expect(fakeClient.createPullRequest).toHaveBeenCalledWith({
+        owner: 'myorg',
+        repo: 'myrepo',
+        title: input.title,
+        head: input.branchName,
+        body: input.description,
+        changes: [
+          {
+            commit: input.title,
+            files: {
+              'catpants.md': {
+                content: Buffer.from('cat + pants').toString('base64'),
+                encoding: 'base64',
+                mode: '100644',
+              },
+              'foobar.txt': {
+                content: Buffer.from('Hello there!').toString('base64'),
+                encoding: 'base64',
+                mode: '100644',
+              },
+            },
+          },
+        ],
+      });
+    });
+
+    describe('when files are marked for deletion', () => {
+      beforeEach(() => {
+        mockDir.setContent({
+          [workspacePath]: {
+            'foo.txt': 'Hello there!',
+            'im-here-to-be-deleted': deletionMarker,
+            'baz.txt': 'baz text',
+            'delete-me-too': deletionMarker,
+          },
+        });
+      });
+
+      it('should delete marked files', async () => {
+        await instance.handler(ctx);
+
+        expect(fakeClient.createPullRequest).toHaveBeenCalledWith({
+          owner: 'myorg',
+          repo: 'myrepo',
+          title: input.title,
+          head: input.branchName,
+          body: input.description,
+          changes: [
+            {
+              commit: input.title,
+              files: {
+                'foo.txt': {
+                  content: Buffer.from('Hello there!').toString('base64'),
+                  encoding: 'base64',
+                  mode: '100644',
+                },
+                'im-here-to-be-deleted': DELETE_FILE,
+                'baz.txt': {
+                  content: Buffer.from('baz text').toString('base64'),
+                  encoding: 'base64',
+                  mode: '100644',
+                },
+                'delete-me-too': DELETE_FILE,
+              },
+            },
+          ],
+        });
+      });
+    });
+  });
+
   describe('with repoUrl', () => {
     let input: GithubPullRequestActionInput;
     let ctx: ActionContext<GithubPullRequestActionInput, any, any>;

plugins/scaffolder-backend-module-github/src/actions/githubPullRequest.ts

@@ -27,7 +27,10 @@ import {
 } from '@backstage/plugin-scaffolder-node';
 import { Octokit } from 'octokit';
 import { CustomErrorBase, InputError } from '@backstage/errors';
-import { createPullRequest } from 'octokit-plugin-create-pull-request';
+import {
+  createPullRequest,
+  DELETE_FILE,
+} from 'octokit-plugin-create-pull-request';
 import { getOctokitOptions } from '../util';
 import { examples } from './githubPullRequest.examples';
 import {
@@ -143,6 +146,15 @@ export const createPublishGithubPullRequestAction = (
           z.string({
             description: 'The name for the branch',
           }),
+        deletionMarker: z =>
+          z
+            .string({
+              description: 'Contents of files that will be deleted',
+            })
+            .min(33, {
+              message: 'deletion marker must be at least 33 characters long',
+            })
+            .optional(),
         targetBranchName: z =>
           z
             .string({
@@ -269,6 +281,7 @@ export const createPublishGithubPullRequestAction = (
       const {
         repoUrl,
         branchName,
+        deletionMarker,
         targetBranchName,
         title,
         description,
@@ -323,24 +336,32 @@ export const createPublishGithubPullRequestAction = (
         file: SerializedFile,
       ): 'utf-8' | 'base64' => (file.symlink ? 'utf-8' : 'base64');
 
+      const encodedDeletionMarker =
+        deletionMarker && Buffer.from(deletionMarker).toString('base64');
       const files = Object.fromEntries(
-        directoryContents.map(file => [
-          targetPath ? path.posix.join(targetPath, file.path) : file.path,
-          {
-            // See the properties of tree items
-            // in https://docs.github.com/en/rest/reference/git#trees
-            mode: determineFileMode(file),
-            // Always use base64 encoding where possible to avoid doubling a binary file in size
-            // due to interpreting a binary file as utf-8 and sending github
-            // the utf-8 encoded content. Symlinks are kept as utf-8 to avoid them
-            // being formatted as a series of scrambled characters
-            //
-            // For example, the original gradle-wrapper.jar is 57.8k in https://github.com/kennethzfeng/pull-request-test/pull/5/files.
-            // Its size could be doubled to 98.3K (See https://github.com/kennethzfeng/pull-request-test/pull/4/files)
-            encoding: determineFileEncoding(file),
-            content: file.content.toString(determineFileEncoding(file)),
-          },
-        ]),
+        directoryContents.map(file => {
+          const content = file.content.toString(determineFileEncoding(file));
+
+          return [
+            targetPath ? path.posix.join(targetPath, file.path) : file.path,
+            content === encodedDeletionMarker
+              ? DELETE_FILE
+              : {
+                  // See the properties of tree items
+                  // in https://docs.github.com/en/rest/reference/git#trees
+                  mode: determineFileMode(file),
+                  // Always use base64 encoding where possible to avoid doubling a binary file in size
+                  // due to interpreting a binary file as utf-8 and sending github
+                  // the utf-8 encoded content. Symlinks are kept as utf-8 to avoid them
+                  // being formatted as a series of scrambled characters
+                  //
+                  // For example, the original gradle-wrapper.jar is 57.8k in https://github.com/kennethzfeng/pull-request-test/pull/5/files.
+                  // Its size could be doubled to 98.3K (See https://github.com/kennethzfeng/pull-request-test/pull/4/files)
+                  encoding: determineFileEncoding(file),
+                  content,
+                },
+          ];
+        }),
       );
 
       // If this is a dry run, log and return