From aa892fccc5ff61158ffa0e3898c008017afc50a4 Mon Sep 17 00:00:00 2001
From: Patrik Oldsberg <poldsberg@gmail.com>
Date: Sun, 13 Feb 2022 21:27:01 +0100
Subject: [PATCH] cli: added package graph utility to list changed packages

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
---
 .../cli/src/lib/monorepo/PackageGraph.test.ts | 36 ++++++++++++++-
 packages/cli/src/lib/monorepo/PackageGraph.ts | 45 +++++++++++++++++++
 2 files changed, 79 insertions(+), 2 deletions(-)

diff --git a/packages/cli/src/lib/monorepo/PackageGraph.test.ts b/packages/cli/src/lib/monorepo/PackageGraph.test.ts
index e8e531bc93..06427a7313 100644
--- a/packages/cli/src/lib/monorepo/PackageGraph.test.ts
+++ b/packages/cli/src/lib/monorepo/PackageGraph.test.ts
@@ -15,8 +15,20 @@
  */
 
 import { getPackages } from '@manypkg/get-packages';
-import { paths } from '../paths';
 import { PackageGraph } from './PackageGraph';
+import { listChangedFiles } from '../git';
+
+jest.mock('../git');
+
+const mockListChangedFiles = listChangedFiles as jest.MockedFunction<
+  typeof listChangedFiles
+>;
+
+jest.mock('../paths', () => ({
+  paths: {
+    targetRoot: '/',
+  },
+}));
 
 const testPackages = [
   {
@@ -53,7 +65,7 @@ const testPackages = [
 
 describe('PackageGraph', () => {
   it('is able to construct a graph from this repo', async () => {
-    const { packages } = await getPackages(paths.ownDir);
+    const { packages } = await getPackages(__dirname);
     const graph = PackageGraph.fromPackages(packages);
     expect(graph.has('@backstage/cli')).toBe(true);
   });
@@ -124,4 +136,24 @@ describe('PackageGraph', () => {
       `Package 'unknown' not found`,
     );
   });
+
+  it('lists changed packages', async () => {
+    const graph = PackageGraph.fromPackages(testPackages);
+
+    mockListChangedFiles.mockResolvedValueOnce(
+      [
+        'README.md',
+        'packages/a/src/foo.ts',
+        'packages/a/src/bar.ts',
+        'packages/b/package.json',
+        'packages/f/src/foo.ts',
+        'packages/f/README.md',
+        'plugins/foo/src/index.ts',
+      ].sort(),
+    );
+
+    await expect(
+      graph.listChangedPackages({ ref: 'origin/master' }),
+    ).resolves.toEqual([graph.get('a'), graph.get('b')]);
+  });
 });
diff --git a/packages/cli/src/lib/monorepo/PackageGraph.ts b/packages/cli/src/lib/monorepo/PackageGraph.ts
index 89d5f79cd2..a1f77299df 100644
--- a/packages/cli/src/lib/monorepo/PackageGraph.ts
+++ b/packages/cli/src/lib/monorepo/PackageGraph.ts
@@ -14,9 +14,11 @@
  * limitations under the License.
  */
 
+import { relative as relativePath, posix as posixPath } from 'path';
 import { getPackages, Package } from '@manypkg/get-packages';
 import { paths } from '../paths';
 import { PackageRole } from '../role';
+import { listChangedFiles } from '../git';
 
 type PackageJSON = Package['packageJson'];
 
@@ -158,4 +160,47 @@ export class PackageGraph extends Map<string, PackageGraphNode> {
 
     return targets;
   }
+
+  async listChangedPackages(options: { ref: string }) {
+    const changedFiles = await listChangedFiles(options.ref);
+
+    const dirMap = new Map(
+      Array.from(this.values()).map(pkg => [
+        posixPath.normalize(relativePath(paths.targetRoot, pkg.dir)) +
+          posixPath.sep,
+        pkg,
+      ]),
+    );
+    const packageDirs = Array.from(dirMap.keys());
+
+    const result = new Array<PackageGraphNode>();
+    let searchIndex = 0;
+
+    changedFiles.sort();
+    packageDirs.sort();
+
+    for (const packageDir of packageDirs) {
+      // Skip through changes that appear before our package dir
+      while (
+        searchIndex < changedFiles.length &&
+        changedFiles[searchIndex] < packageDir
+      ) {
+        searchIndex += 1;
+      }
+
+      // Check if we arrived at a match, otherwise we move on to the next package dir
+      if (changedFiles[searchIndex]?.startsWith(packageDir)) {
+        searchIndex += 1;
+
+        result.push(dirMap.get(packageDir)!);
+
+        // Skip through the rest of the changed files for the same package
+        while (changedFiles[searchIndex]?.startsWith(packageDir)) {
+          searchIndex += 1;
+        }
+      }
+    }
+
+    return result;
+  }
 }