Lockfile trailing newline fix and normalization for frozen lockfile comparison

.vscode/extensions.json

@@ -1,5 +1,6 @@
 {
 	"recommendations": [
 		"dbaeumer.vscode-eslint",
+		"hbenl.vscode-mocha-test-adapter"
 	]
 }

.vscode/settings.json

@@ -3,21 +3,21 @@
     "search.exclude": {
         "dist": true
     },
-    "typescript.tsc.autoDetect": "off",
+    "js/ts.tsc.autoDetect": "off",
     "eslint.options": {
         "rulePaths": [
             "./build/eslint"
         ]
     },
-    "mochaExplorer.files": "test/**/*.test.ts",
+    "mochaExplorer.files": "src/test/**/*.test.ts",
     "mochaExplorer.require": "ts-node/register",
     "mochaExplorer.env": {
         "TS_NODE_PROJECT": "src/test/tsconfig.json"
     },
     "files.associations": {
         "devcontainer-features.json": "jsonc"
     },
-    "typescript.tsdk": "node_modules/typescript/lib",
+    "js/ts.tsdk.path": "node_modules/typescript/lib",
     "git.branchProtection": [
         "main",
         "release/*"

src/spec-configuration/lockfile.ts

@@ -53,12 +53,24 @@ export async function writeLockfile(params: ContainerFeatureInternalParams, conf
 		return;
 	}
 
-	const newLockfileContentString = JSON.stringify(lockfile, null, 2);
+	// Trailing newline per POSIX convention
+	const newLockfileContentString = JSON.stringify(lockfile, null, 2) + '\n';
 	const newLockfileContent = Buffer.from(newLockfileContentString);
 	if (params.experimentalFrozenLockfile && !oldLockfileContent) {
 		throw new Error('Lockfile does not exist.');
 	}
-	if (!oldLockfileContent || !newLockfileContent.equals(oldLockfileContent)) {
+	// Normalize the existing lockfile through JSON.parse -> JSON.stringify to produce
+	// the same canonical format as newLockfileContentString, so that the string comparison
+	// below ignores cosmetic differences (indentation, trailing whitespace, etc.).
+	let oldLockfileNormalized: string | undefined;
+	if (oldLockfileContent) {
+		try {
+			oldLockfileNormalized = JSON.stringify(JSON.parse(oldLockfileContent.toString()), null, 2) + '\n';
+		} catch {
+			// Empty or invalid JSON; treat as needing rewrite.
+		}
+	}
+	if (!oldLockfileNormalized || oldLockfileNormalized !== newLockfileContentString) {
 		if (params.experimentalFrozenLockfile) {
 			throw new Error('Lockfile does not match.');
 		}

src/test/container-features/configs/lockfile-dependson/expected.devcontainer-lock.json

@@ -27,4 +27,4 @@
       ]
     }
   }
-}
+}

src/test/container-features/configs/lockfile-frozen-no-lockfile/.devcontainer.json

@@ -0,0 +1,7 @@
+{
+	"image": "mcr.microsoft.com/devcontainers/base:ubuntu",
+	"features": {
+		"ghcr.io/codspace/features/flower:1": {},
+		"ghcr.io/codspace/features/color:1": {}
+	}
+}

src/test/container-features/configs/lockfile-frozen/.devcontainer-lock.json

@@ -11,4 +11,4 @@
       "integrity": "sha256:c9cc1ac636b9ef595512b5ca7ecb3a35b7d3499cb6f86372edec76ae0cd71d43"
     }
   }
-}
+}

src/test/container-features/configs/lockfile-outdated/expected.devcontainer-lock.json

@@ -11,4 +11,4 @@
       "integrity": "sha256:c9cc1ac636b9ef595512b5ca7ecb3a35b7d3499cb6f86372edec76ae0cd71d43"
     }
   }
-}
+}

src/test/container-features/configs/lockfile-upgrade-command/upgraded.devcontainer-lock.json

@@ -21,4 +21,4 @@
       "integrity": "sha256:9024deeca80347dea7603a3bb5b4951988f0bf5894ba036a6ee3f29c025692c6"
     }
   }
-}
+}

src/test/container-features/configs/lockfile/expected.devcontainer-lock.json

@@ -16,4 +16,4 @@
       "integrity": "sha256:41607bd6aba3975adcd0641cc479e67b04abd21763ba8a41ea053bcc04a6a818"
     }
   }
-}
+}

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

@@ -7,7 +7,7 @@ import * as assert from 'assert';
 import * as path from 'path';
 import * as semver from 'semver';
 import { shellExec } from '../testUtils';
-import { cpLocal, readLocalFile, rmLocal } from '../../spec-utils/pfs';
+import { cpLocal, readLocalFile, rmLocal, writeLocalFile } from '../../spec-utils/pfs';
 
 const pkg = require('../../../package.json');
 
@@ -279,6 +279,44 @@ describe('Lockfile', function () {
 		}
 	});
 
+	it('lockfile ends with trailing newline', async () => {
+		const workspaceFolder = path.join(__dirname, 'configs/lockfile');
+
+		const lockfilePath = path.join(workspaceFolder, '.devcontainer-lock.json');
+		await rmLocal(lockfilePath, { force: true });
+
+		const res = await shellExec(`${cli} build --workspace-folder ${workspaceFolder} --experimental-lockfile`);
+		const response = JSON.parse(res.stdout);
+		assert.equal(response.outcome, 'success');
+		const actual = (await readLocalFile(lockfilePath)).toString();
+		assert.ok(actual.endsWith('\n'), 'Lockfile should end with a trailing newline');
+	});
+
+	it('frozen lockfile matches despite formatting differences', async () => {
+		const workspaceFolder = path.join(__dirname, 'configs/lockfile-frozen');
+		const lockfilePath = path.join(workspaceFolder, '.devcontainer-lock.json');
+
+		// Read the existing lockfile, strip trailing newline to create a byte-different but semantically identical file
+		const original = (await readLocalFile(lockfilePath)).toString();
+		const stripped = original.replace(/\n$/, '');
+		assert.notEqual(original, stripped, 'Test setup: should have removed trailing newline');
+		assert.deepEqual(JSON.parse(original), JSON.parse(stripped), 'Test setup: JSON content should be identical');
+
+		try {
+			await writeLocalFile(lockfilePath, Buffer.from(stripped));
+
+			// Frozen lockfile should succeed because JSON content is the same
+			const res = await shellExec(`${cli} build --workspace-folder ${workspaceFolder} --experimental-lockfile --experimental-frozen-lockfile`);
+			const response = JSON.parse(res.stdout);
+			assert.equal(response.outcome, 'success', 'Frozen lockfile should not fail when only formatting differs');
+			const actual = (await readLocalFile(lockfilePath)).toString();
+			assert.strictEqual(actual, stripped, 'Frozen lockfile should remain unchanged when only formatting differs');
+		} finally {
+			// Restore original lockfile
+			await writeLocalFile(lockfilePath, Buffer.from(original));
+		}
+	});
+
 	it('upgrade command should work with default workspace folder', async () => {
 		const workspaceFolder = path.join(__dirname, 'configs/lockfile-upgrade-command');
 		const absoluteTmpPath = path.resolve(__dirname, 'tmp');
@@ -298,4 +336,68 @@ describe('Lockfile', function () {
 			process.chdir(originalCwd);
 		}
 	});
+
+	it('frozen lockfile fails when lockfile does not exist', async () => {
+		const workspaceFolder = path.join(__dirname, 'configs/lockfile-frozen-no-lockfile');
+		const lockfilePath = path.join(workspaceFolder, '.devcontainer-lock.json');
+		await rmLocal(lockfilePath, { force: true });
+
+		try {
+			throw await shellExec(`${cli} build --workspace-folder ${workspaceFolder} --experimental-lockfile --experimental-frozen-lockfile`);
+		} catch (res) {
+			const response = JSON.parse(res.stdout);
+			assert.equal(response.outcome, 'error');
+			assert.equal(response.message, 'Lockfile does not exist.');
+		}
+	});
+
+	it('corrupt lockfile causes build error', async () => {
+		const workspaceFolder = path.join(__dirname, 'configs/lockfile');
+		const lockfilePath = path.join(workspaceFolder, '.devcontainer-lock.json');
+		const expectedPath = path.join(workspaceFolder, 'expected.devcontainer-lock.json');
+
+		try {
+			// Write invalid JSON to the lockfile
+			await writeLocalFile(lockfilePath, Buffer.from('this is not valid json{{{'));
+
+			try {
+				throw await shellExec(`${cli} build --workspace-folder ${workspaceFolder} --experimental-lockfile`);
+			} catch (res) {
+				const response = JSON.parse(res.stdout);
+				assert.equal(response.outcome, 'error');
+			}
+		} finally {
+			// Restore from the known-good expected lockfile
+			await cpLocal(expectedPath, lockfilePath);
+		}
+	});
+
+	it('no lockfile flags and no existing lockfile is a no-op', async () => {
+		const workspaceFolder = path.join(__dirname, 'configs/lockfile');
+		const lockfilePath = path.join(workspaceFolder, '.devcontainer-lock.json');
+		const expectedPath = path.join(workspaceFolder, 'expected.devcontainer-lock.json');
+
+		try {
+			await rmLocal(lockfilePath, { force: true });
+
+			// Build without any lockfile flags
+			const res = await shellExec(`${cli} build --workspace-folder ${workspaceFolder}`);
+			const response = JSON.parse(res.stdout);
+			assert.equal(response.outcome, 'success');
+
+			// Lockfile should not have been created
+			let exists = true;
+			await readLocalFile(lockfilePath).catch(err => {
+				if (err?.code === 'ENOENT') {
+					exists = false;
+				} else {
+					throw err;
+				}
+			});
+			assert.equal(exists, false, 'Lockfile should not be created when no lockfile flags are set');
+		} finally {
+			// Restore from the known-good expected lockfile
+			await cpLocal(expectedPath, lockfilePath);
+		}
+	});
 });

src/test/tsconfig.json

@@ -1,7 +1,11 @@
 {
 	"extends": "../../tsconfig.base.json",
 	"compilerOptions": {
-		"resolveJsonModule": true
+		"resolveJsonModule": true,
+		"types": [
+			"node",
+			"mocha"
+		]
 	},
 	"references": [
 		{