Empty lockfiles will trigger lockfile to init/populate

src/spec-configuration/containerFeaturesConfiguration.ts

@@ -547,7 +547,7 @@ export async function generateFeaturesConfig(params: ContainerFeatureInternalPar
 
 	const ociCacheDir = await prepareOCICache(dstFolder);
 
-	const lockfile = await readLockfile(config);
+	const { lockfile, initLockfile } = await readLockfile(config);
 
 	const processFeature = async (_userFeature: DevContainerFeature) => {
 		return await processFeatureIdentifier(params, configPath, workspaceRoot, _userFeature, lockfile);
@@ -570,7 +570,7 @@ export async function generateFeaturesConfig(params: ContainerFeatureInternalPar
 	await fetchFeatures(params, featuresConfig, locallyCachedFeatureSet, dstFolder, localFeaturesFolder, ociCacheDir, lockfile);
 
 	await logFeatureAdvisories(params, featuresConfig);
-	await writeLockfile(params, config, featuresConfig);
+	await writeLockfile(params, config, featuresConfig, initLockfile);
 	return featuresConfig;
 }
 
@@ -582,7 +582,7 @@ export async function loadVersionInfo(params: ContainerFeatureInternalParams, co
 		return { features: {} };
 	}
 
-	const lockfile = await readLockfile(config);
+	const { lockfile } = await readLockfile(config);
 
 	const features: Record<string, any> = {};
 

src/spec-configuration/lockfile.ts

@@ -13,7 +13,7 @@ export interface Lockfile {
 	features: Record<string, { version: string; resolved: string; integrity: string }>;
 }
 
-export async function writeLockfile(params: ContainerFeatureInternalParams, config: DevContainerConfig, featuresConfig: FeaturesConfig) {
+export async function writeLockfile(params: ContainerFeatureInternalParams, config: DevContainerConfig, featuresConfig: FeaturesConfig, forceInitLockfile?: boolean) {
 	const lockfilePath = getLockfilePath(config);
 	const oldLockfileContent = await readLocalFile(lockfilePath)
 		.catch(err => {
@@ -22,7 +22,7 @@ export async function writeLockfile(params: ContainerFeatureInternalParams, conf
 			}
 		});
 
-	if (!oldLockfileContent && !params.experimentalLockfile && !params.experimentalFrozenLockfile) {
+	if (!forceInitLockfile && !oldLockfileContent && !params.experimentalLockfile && !params.experimentalFrozenLockfile) {
 		return;
 	}
 
@@ -63,13 +63,17 @@ export async function writeLockfile(params: ContainerFeatureInternalParams, conf
 	}
 }
 
-export async function readLockfile(config: DevContainerConfig): Promise<Lockfile | undefined> {
+export async function readLockfile(config: DevContainerConfig): Promise<{ lockfile?: Lockfile; initLockfile?: boolean }> {
 	try {
 		const content = await readLocalFile(getLockfilePath(config));
-		return JSON.parse(content.toString()) as Lockfile;
+		// If empty file, use as maker to initialize lockfile when build completes.
+		if (content.toString().trim() === '') {
+			return { initLockfile: true };
+		}
+		return { lockfile: JSON.parse(content.toString()) as Lockfile };
 	} catch (err) {
 		if (err?.code === 'ENOENT') {
-			return undefined;
+			return {};
 		}
 		throw err;
 	}

src/spec-node/featuresCLI/resolveDependencies.ts

@@ -83,7 +83,7 @@ async function featuresResolveDependencies({
 		env: process.env,
 	};
 
-	const lockfile = await readLockfile(config);
+	const { lockfile } = await readLockfile(config);
 	const processFeature = async (_userFeature: DevContainerFeature) => {
 		return await processFeatureIdentifier(params, configPath, workspaceFolder, _userFeature, lockfile);
 	};

src/test/container-features/configs/lockfile-generate-from-empty-file-frozen/.devcontainer/devcontainer.json

@@ -0,0 +1,6 @@
+{
+	"image": "mcr.microsoft.com/devcontainers/base",
+	"features": {
+		"ghcr.io/devcontainers/features/dotnet:2": {}
+	}
+}

src/test/container-features/configs/lockfile-generate-from-empty-file/.devcontainer/devcontainer.json

@@ -0,0 +1,6 @@
+{
+	"image": "mcr.microsoft.com/devcontainers/base",
+	"features": {
+		"ghcr.io/devcontainers/features/dotnet:2": {}
+	}
+}

src/test/container-features/lockfile.test.ts

@@ -138,4 +138,41 @@ describe('Lockfile', function () {
 			assert.equal(response.outcome, 'error');
 		}
 	});
+
+	it('empty lockfile should init', async () => {
+		const workspaceFolder = path.join(__dirname, 'configs/lockfile-generate-from-empty-file');
+		const lockfilePath = path.join(workspaceFolder, '.devcontainer', 'devcontainer-lock.json');
+		const cleanup = async () => {
+			await rmLocal(lockfilePath, { force: true });
+			await shellExec(`touch ${lockfilePath}`);
+		};
+
+		await cleanup();
+		const res = await shellExec(`${cli} build --workspace-folder ${workspaceFolder}`);
+		const response = JSON.parse(res.stdout);
+		assert.equal(response.outcome, 'success');
+		const actual = JSON.parse((await readLocalFile(lockfilePath)).toString());
+		assert.ok(actual.features['ghcr.io/devcontainers/features/dotnet:2']);
+		await cleanup();
+	});
+
+	it('empty lockfile should not init when frozen', async () => {
+		const workspaceFolder = path.join(__dirname, 'configs/lockfile-generate-from-empty-file-frozen');
+		const lockfilePath = path.join(workspaceFolder, '.devcontainer', 'devcontainer-lock.json');
+		const cleanup = async () => {
+			await rmLocal(lockfilePath, { force: true });
+			await shellExec(`touch ${lockfilePath}`);
+		};
+
+		await cleanup();
+		try {
+			await shellExec(`${cli} build --workspace-folder ${workspaceFolder} --experimental-frozen-lockfile`);
+			await cleanup();
+		} catch (res) {
+			const response = JSON.parse(res.stdout);
+			assert.equal(response.outcome, 'error');
+			assert.equal(response.message, 'Lockfile does not match.');
+			await cleanup();
+		}
+	});
 });