feat: force node 15 for lerna when npm lockfileVersion=2

lib/manager/npm/post-update/lerna.ts

@@ -79,7 +79,8 @@ export async function generateLockFiles(
       lernaCommand = lernaCommand.replace('--ignore-scripts ', '');
     }
     lernaCommand += cmdOptions;
-    const tagConstraint = await getNodeConstraint(config);
+    const allowUnstable = true; // lerna will pick the default installed npm@6 unless we use node@>=15
+    const tagConstraint = await getNodeConstraint(config, allowUnstable);
     const execOptions: ExecOptions = {
       cwd,
       extraEnv: {

lib/manager/npm/post-update/node-version.spec.ts

@@ -28,6 +28,33 @@ describe('getNodeConstraint', () => {
     const node16IsStable = isStable('16.100.0');
     expect(isAugmentedRange || node16IsStable).toBe(true);
   });
+  it('forces node 15 if v2 lockfile detected and constraint allows', async () => {
+    fs.readLocalFile.mockResolvedValueOnce(null);
+    fs.readLocalFile.mockResolvedValueOnce(null);
+    fs.readLocalFile.mockResolvedValueOnce('{"lockfileVersion":2}');
+    const res = await getNodeConstraint({
+      ...config,
+      constraints: { node: '>= 12.16.0' },
+    });
+    const isAugmentedRange = res === '>=15';
+    const node16IsStable = isStable('16.100.0');
+    expect(isAugmentedRange || node16IsStable).toBe(true);
+  });
+  it('forces node 15 if v2 lockfile detected and no constraint', async () => {
+    fs.readLocalFile.mockResolvedValueOnce(null);
+    fs.readLocalFile.mockResolvedValueOnce(null);
+    fs.readLocalFile.mockResolvedValueOnce('{"lockfileVersion":2}');
+    const res = await getNodeConstraint(
+      {
+        ...config,
+        constraints: {},
+      },
+      true
+    );
+    const isAugmentedRange = res === '>=15';
+    const node16IsStable = isStable('16.100.0');
+    expect(isAugmentedRange || node16IsStable).toBe(true);
+  });
   it('returns .node-version value', async () => {
     fs.readLocalFile = jest.fn();
     fs.readLocalFile.mockResolvedValueOnce(null);

lib/manager/npm/post-update/node-version.ts

@@ -29,26 +29,42 @@ function getPackageJsonConstraint(config: PostUpdateConfig): string | null {
 }
 
 export async function getNodeConstraint(
-  config: PostUpdateConfig
+  config: PostUpdateConfig,
+  allowUnstable = false
 ): Promise<string> | null {
   const { packageFile } = config;
   let constraint =
     (await getNodeFile(getSiblingFileName(packageFile, '.nvmrc'))) ||
     (await getNodeFile(getSiblingFileName(packageFile, '.node-version'))) ||
     getPackageJsonConstraint(config);
+  let lockfileVersion = 1;
+  try {
+    const lockFileName = getSiblingFileName(packageFile, 'package-lock.json');
+    lockfileVersion = JSON.parse(await readLocalFile(lockFileName, 'utf8'))
+      .lockfileVersion;
+  } catch (err) {
+    // do nothing
+  }
   // Avoid using node 15 if node 14 also satisfies the same constraint
   // Remove this once node 16 is LTS
   if (constraint) {
     if (
       validRange(constraint) &&
       satisfies('14.100.0', constraint) &&
       satisfies('15.100.0', constraint) &&
-      !isStable('16.100.0') && // this should return false as soon as Node 16 is LTS
-      validRange(`${constraint} <15`)
+      !isStable('16.100.0')
     ) {
-      logger.debug('Augmenting constraint to avoid node 15');
-      constraint = `${constraint} <15`;
+      if (lockfileVersion === 2) {
+        logger.debug('Forcing node 15 to ensure lockfileVersion=2 is used');
+        constraint = '>=15';
+      } else if (validRange(`${constraint} <15`)) {
+        logger.debug('Augmenting constraint to avoid node 15');
+        constraint = `${constraint} <15`;
+      }
     }
+  } else if (allowUnstable && lockfileVersion === 2) {
+    logger.debug('Using node >=15 for lockfileVersion=2');
+    constraint = '>=15';
   } else {
     logger.debug('No node constraint found - using latest');
   }