Merge pull request #118 from useblacksmith/builder-misconfig

fix: use correct platform when creating remote buildx builder

.github/workflows/builder-platform-tests.yml

@@ -0,0 +1,99 @@
+name: Builder platform matrix tests
+
+on:
+  workflow_dispatch:
+  pull_request:
+
+jobs:
+  # 1) Build AMD image on default (amd64) runner
+  amd_on_amd:
+    name: linux/amd64 build on blacksmith runner
+    runs-on: blacksmith
+    steps:
+      - name: Checkout source
+        uses: actions/checkout@v4
+
+      - name: Write sample Dockerfile
+        run: |
+          cat <<'EOF' > Dockerfile
+          FROM alpine:3.20
+          # Install something non-trivial so that layer caching is observable
+          RUN apk add --no-cache curl git
+          EOF
+
+      - name: Build image (linux/amd64)
+        uses: useblacksmith/build-push-action@builder-misconfig
+        with:
+          context: .
+          platforms: linux/amd64
+          push: false
+          tags: test/amd_on_amd:${{ github.sha }}
+
+  # 2) Build ARM image on default (amd64) runner
+  arm_on_amd:
+    name: linux/arm64 build on blacksmith runner
+    runs-on: blacksmith
+    steps:
+      - name: Checkout source
+        uses: actions/checkout@v4
+
+      - name: Write sample Dockerfile
+        run: |
+          cat <<'EOF' > Dockerfile
+          FROM alpine:3.20
+          RUN apk add --no-cache curl git
+          EOF
+
+      - name: Build image (linux/arm64)
+        uses: useblacksmith/build-push-action@builder-misconfig
+        with:
+          context: .
+          platforms: linux/arm64
+          push: false
+          tags: test/arm_on_amd:${{ github.sha }}
+
+  # 3) Build AMD image on ARM runner
+  amd_on_arm:
+    name: linux/amd64 build on blacksmith-arm runner
+    runs-on: blacksmith-arm
+    steps:
+      - name: Checkout source
+        uses: actions/checkout@v4
+
+      - name: Write sample Dockerfile
+        run: |
+          cat <<'EOF' > Dockerfile
+          FROM alpine:3.20
+          RUN apk add --no-cache curl git
+          EOF
+
+      - name: Build image (linux/amd64)
+        uses: useblacksmith/build-push-action@builder-misconfig
+        with:
+          context: .
+          platforms: linux/amd64
+          push: false
+          tags: test/amd_on_arm:${{ github.sha }}
+
+  # 4) Build ARM image on ARM runner
+  arm_on_arm:
+    name: linux/arm64 build on blacksmith-arm runner
+    runs-on: blacksmith-arm
+    steps:
+      - name: Checkout source
+        uses: actions/checkout@v4
+
+      - name: Write sample Dockerfile
+        run: |
+          cat <<'EOF' > Dockerfile
+          FROM alpine:3.20
+          RUN apk add --no-cache curl git
+          EOF
+
+      - name: Build image (linux/arm64)
+        uses: useblacksmith/build-push-action@builder-misconfig
+        with:
+          context: .
+          platforms: linux/arm64
+          push: false
+          tags: test/arm_on_arm:${{ github.sha }} 

package.json

@@ -40,7 +40,7 @@
   },
   "devDependencies": {
     "@babel/core": "^7.26.10",
-    "@babel/preset-env": "^7.26.9",
+    "@babel/preset-env": "^7.27.2",
     "@babel/preset-typescript": "^7.27.0",
     "@types/jest": "^29.5.14",
     "@types/node": "^20.12.12",

src/__mocks__/@buf/blacksmith_vm-agent.bufbuild_es/stickydisk/v1/stickydisk_pb.ts

@@ -9,4 +9,4 @@ export class Metric {
   type: Metric_MetricType = Metric_MetricType.UNSPECIFIED;
   value: number = 0;
   labels: Record<string, string> = {};
-} 
+}

src/__mocks__/@buf/blacksmith_vm-agent.connectrpc_es/stickydisk/v1/stickydisk_connect.ts

@@ -1,23 +1,23 @@
 export class StickyDiskService {
   constructor() {}
-  
+
   async commitStickyDisk() {
     return {};
   }
-  
+
   async getStickyDisk() {
     return {};
   }
-  
+
   async queueDockerJob() {
     return {};
   }
-  
+
   async reportMetric() {
     return {};
   }
-  
+
   async up() {
     return {};
   }
-} 
+}

src/__mocks__/execa.ts

@@ -4,4 +4,4 @@ export const execa = jest.fn().mockImplementation(() => {
     stderr: '',
     exitCode: 0
   };
-}); 
+});

src/__tests__/remote-builder-args.test.ts

@@ -0,0 +1,40 @@
+import * as os from 'os';
+import {getRemoteBuilderArgs, resolveRemoteBuilderPlatforms} from '../context';
+
+jest.mock('@actions/core', () => ({
+  info: jest.fn(),
+  debug: jest.fn(),
+  warning: jest.fn(),
+  error: jest.fn()
+}));
+
+describe('Remote builder platform argument resolution', () => {
+  const builderName = 'test-builder';
+  const builderUrl = 'tcp://127.0.0.1:1234';
+
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  test('returns comma-separated list when platforms are supplied', async () => {
+    const platforms = ['linux/arm64', 'linux/amd64'];
+    const platformStr = resolveRemoteBuilderPlatforms(platforms);
+    expect(platformStr).toBe('linux/arm64,linux/amd64');
+
+    const args = await getRemoteBuilderArgs(builderName, builderUrl, platforms);
+    const idx = args.indexOf('--platform');
+    expect(idx).toBeGreaterThan(-1);
+    expect(args[idx + 1]).toBe('linux/arm64,linux/amd64');
+  });
+
+  test('falls back to host architecture when no platforms supplied', async () => {
+    const platformStr = resolveRemoteBuilderPlatforms([]);
+    const expectedPlatform = os.arch() === 'arm64' ? 'linux/arm64' : 'linux/amd64';
+    expect(platformStr).toBe(expectedPlatform);
+
+    const args = await getRemoteBuilderArgs(builderName, builderUrl, []);
+    const idx = args.indexOf('--platform');
+    expect(idx).toBeGreaterThan(-1);
+    expect(args[idx + 1]).toBe(expectedPlatform);
+  });
+});

src/context.ts

@@ -1,6 +1,6 @@
 import * as core from '@actions/core';
 import * as handlebars from 'handlebars';
-import * as fs from 'fs';
+import * as os from 'os';
 
 import {Build} from '@docker/actions-toolkit/lib/buildx/build';
 import {Context} from '@docker/actions-toolkit/lib/context';
@@ -336,12 +336,39 @@ export const tlsClientKeyPath = '/tmp/blacksmith_client_key.pem';
 export const tlsClientCaCertificatePath = '/tmp/blacksmith_client_ca_certificate.pem';
 export const tlsRootCaCertificatePath = '/tmp/blacksmith_root_ca_certificate.pem';
 
-export async function getRemoteBuilderArgs(name: string, builderUrl: string): Promise<Array<string>> {
+/**
+ * Resolve the platform list that should be passed to `docker buildx create`.
+ *
+ * Priority:
+ *   1. Use the user-supplied platforms list (comma-joined) if provided.
+ *   2. Fallback to the architecture of the host runner.
+ *
+ * The function is exported to allow isolated unit testing.
+ */
+export function resolveRemoteBuilderPlatforms(platforms?: string[]): string {
+  // If user explicitly provided platforms, honour them verbatim.
+  if (platforms && platforms.length > 0) {
+    return platforms.join(',');
+  }
+
+  // Otherwise derive from host architecture.
+  const nodeArch = os.arch(); // e.g. 'x64', 'arm64', 'arm'
+  const archMap: {[key: string]: string} = {
+    x64: 'amd64',
+    arm64: 'arm64',
+    arm: 'arm'
+  };
+  const mappedArch = archMap[nodeArch] || nodeArch;
+  return `linux/${mappedArch}`;
+}
+
+export async function getRemoteBuilderArgs(name: string, builderUrl: string, platforms?: string[]): Promise<Array<string>> {
   const args: Array<string> = ['create', '--name', name, '--driver', 'remote'];
 
-  // TODO(aayush): Instead of hardcoding the platform, we should fail the build if the platform is
-  // unsupported.
-  args.push('--platform', 'linux/amd64');
+  const platformFlag = resolveRemoteBuilderPlatforms(platforms);
+  core.info(`Determined remote builder platform(s): ${platformFlag}`);
+  args.push('--platform', platformFlag);
+
   // Always use the remote builder, overriding whatever has been configured so far.
   args.push('--use');
   // Use the provided builder URL

src/main.ts

@@ -202,7 +202,7 @@ actionsToolkit.run(
       if (builderInfo.addr) {
         await core.group(`Creating a builder instance`, async () => {
           const name = `blacksmith-${Date.now().toString(36)}`;
-          const createCmd = await toolkit.buildx.getCommand(await context.getRemoteBuilderArgs(name, builderInfo.addr!));
+          const createCmd = await toolkit.buildx.getCommand(await context.getRemoteBuilderArgs(name, builderInfo.addr!, inputs.platforms));
           core.info(`Creating builder with command: ${createCmd.command}`);
           await Exec.getExecOutput(createCmd.command, createCmd.args, {
             ignoreReturnCode: true