feat(pnpm): support package.json#packageManager

src/ci.ts

@@ -1,9 +1,10 @@
 import { existsSync } from 'fs';
 import { spawnSync } from 'child_process';
+import { detectPnpmVersionFromPackageManager } from './utils/detect-pnpm-version-from-package-manager.js';
 import { guessPnpmVersion } from './utils/guess-pnpm-version.js';
 import { getPnpmLockVersion } from './utils/get-pnpm-lock-version.js';
-import type { NodeVersion } from './types.js';
 import { parseVersionString } from './utils/parse-version-string.js';
+import type { NodeVersion } from './types.js';
 
 export const ci = async () => {
 	const options = {
@@ -26,10 +27,14 @@ export const ci = async () => {
 	}
 
 	if (existsSync('pnpm-lock.yaml')) {
-		const pnpmVersion = guessPnpmVersion(
-			parseVersionString<NodeVersion>(process.versions.node),
-			await getPnpmLockVersion(),
+		const pnpmVersion = (
+			detectPnpmVersionFromPackageManager()
+			|| guessPnpmVersion(
+				parseVersionString<NodeVersion>(process.versions.node),
+				await getPnpmLockVersion(),
+			)
 		);
+
 		return spawnSync(
 			'npx',
 			[`pnpm${pnpmVersion}`, 'i', '--frozen-lockfile'],

src/utils/detect-pnpm-version-from-package-manager.ts

@@ -0,0 +1,20 @@
+import { readFileSync } from 'fs';
+
+/**
+ * This is specific to pnpm because it's the only package manager with
+ * incompatibility between the lockfile and the package manager version.
+ *
+ * The source of truth is still the lock file type because `npm ci` only
+ * installs from the lock file.
+ *
+ * That's to say if there's a package-lock.json, but the packageManager
+ * is pnpm, then we'll still use npm.
+ */
+export const detectPnpmVersionFromPackageManager = () => {
+	try {
+		const { packageManager } = JSON.parse(readFileSync('package.json', 'utf8'));
+		if (packageManager.startsWith('pnpm')) {
+			return packageManager.slice(4);
+		}
+	} catch {}
+};

tests/fixtures/pnpm-package-manager/package.json

@@ -0,0 +1,6 @@
+{
+	"packageManager": "pnpm@8.0.0",
+	"dependencies": {
+		"test-package": "^0.0.1"
+	}
+}

tests/index.ts

@@ -7,7 +7,7 @@ const ciBinaryPath = path.resolve('dist/cli.js');
 const ci = (cwd: string) => execa(ciBinaryPath, [], { cwd });
 
 describe('ci', ({ describe, runTestSuite }) => {
-	describe('lock file', ({ test }) => {
+	describe('lock file', ({ test, describe }) => {
 		test('npm', async ({ onTestFinish }) => {
 			const fixture = await createFixture('tests/fixtures/npm');
 			onTestFinish(async () => await fixture.rm());
@@ -16,23 +16,35 @@ describe('ci', ({ describe, runTestSuite }) => {
 			expect(stdout).toMatch('added 1 package, and audited 2 packages');
 		});
 
-		test('pnpm', async ({ onTestFinish }) => {
-			const fixture = await createFixture('tests/fixtures/pnpm');
-			onTestFinish(async () => await fixture.rm());
-
-			const { stdout } = await ci(fixture.path);
-
-			// pnpm changed "Lockfile is up-to-date" to "Lockfile is up to date"
-			expect(stdout).toMatch('Lockfile is up');
-		});
-
 		test('yarn', async ({ onTestFinish }) => {
 			const fixture = await createFixture('tests/fixtures/yarn');
 			onTestFinish(async () => await fixture.rm());
 
 			const { stdout } = await ci(fixture.path);
 			expect(stdout).toMatch('YN0000: Done in');
 		});
+
+		describe('pnpm', ({ test }) => {
+			test('detect veresion', async ({ onTestFinish }) => {
+				const fixture = await createFixture('tests/fixtures/pnpm');
+				onTestFinish(async () => await fixture.rm());
+
+				const { stdout } = await ci(fixture.path);
+
+				// pnpm changed "Lockfile is up-to-date" to "Lockfile is up to date"
+				expect(stdout).toMatch('Lockfile is up');
+			});
+
+			test('packageManager', async ({ onTestFinish }) => {
+				const fixture = await createFixture('tests/fixtures/pnpm-package-manager');
+				onTestFinish(async () => await fixture.rm());
+
+				const { stdout } = await ci(fixture.path);
+
+				// pnpm changed "Lockfile is up-to-date" to "Lockfile is up to date"
+				expect(stdout).toMatch('Lockfile is up');
+			});
+		});
 	});
 
 	runTestSuite(import('./get-pnpm-version.spec.js'));