fix(lockfile): better lockfile stringify error

.changeset/odd-ears-judge.md

@@ -0,0 +1,5 @@
+---
+"@pnpm/lockfile-file": patch
+---
+
+Print a better when stringifying a lockfile object fails.

packages/lockfile-file/src/write.ts

@@ -1,3 +1,4 @@
+import PnpmError from '@pnpm/error'
 import logger from './logger'
 import { DEPENDENCIES_FIELDS } from '@pnpm/types'
 import { Lockfile, ProjectSnapshot } from '@pnpm/lockfile-types'
@@ -56,11 +57,48 @@ function writeLockfile (
     return rimraf(lockfilePath)
   }
 
-  const yamlDoc = yaml.safeDump(normalizeLockfile(wantedLockfile, opts?.forceSharedFormat === true), LOCKFILE_YAML_FORMAT)
+  const yamlDoc = yamlStringify(wantedLockfile, opts?.forceSharedFormat === true)
 
   return writeFileAtomic(lockfilePath, yamlDoc)
 }
 
+function yamlStringify (lockfile: Lockfile, forceSharedFormat: boolean) {
+  try {
+    return yaml.safeDump(
+      normalizeLockfile(lockfile, forceSharedFormat),
+      LOCKFILE_YAML_FORMAT
+    )
+  } catch (err) {
+    if (err.message.includes('[object Undefined]')) {
+      const brokenValuePath = findBrokenRecord(lockfile)
+      if (brokenValuePath) {
+        throw new PnpmError('LOCKFILE_STRINGIFY', `Failed to stringify the lockfile object. Undefined value at: ${brokenValuePath}`)
+      }
+    }
+    throw err
+  }
+}
+
+function findBrokenRecord (obj: Object): string | null {
+  for (let [key, value] of Object.entries(obj)) {
+    if (key === '.') key = '[.]'
+    switch (typeof value) {
+    case 'undefined': {
+      return key
+    }
+    case 'object': {
+      const brokenKey = findBrokenRecord(value)
+      if (!brokenKey) break
+      if (brokenKey.startsWith('[')) {
+        return `${key}${brokenKey}`
+      }
+      return `${key}.${brokenKey}`
+    }
+    }
+  }
+  return null
+}
+
 function isEmptyLockfile (lockfile: Lockfile) {
   return R.values(lockfile.importers).every((importer) => R.isEmpty(importer.specifiers ?? {}) && R.isEmpty(importer.dependencies ?? {}))
 }
@@ -128,7 +166,7 @@ export default function writeLockfiles (
   }
 
   const forceSharedFormat = opts?.forceSharedFormat === true
-  const yamlDoc = yaml.safeDump(normalizeLockfile(opts.wantedLockfile, forceSharedFormat), LOCKFILE_YAML_FORMAT)
+  const yamlDoc = yamlStringify(opts.wantedLockfile, forceSharedFormat)
 
   // in most cases the `pnpm-lock.yaml` and `node_modules/.pnpm-lock.yaml` are equal
   // in those cases the YAML document can be stringified only once for both files
@@ -148,7 +186,7 @@ export default function writeLockfiles (
     prefix: opts.wantedLockfileDir,
   })
 
-  const currentYamlDoc = yaml.safeDump(normalizeLockfile(opts.currentLockfile, forceSharedFormat), LOCKFILE_YAML_FORMAT)
+  const currentYamlDoc = yamlStringify(opts.currentLockfile, forceSharedFormat)
 
   return Promise.all([
     writeFileAtomic(wantedLockfilePath, yamlDoc),

packages/lockfile-file/test/write.ts

@@ -1,4 +1,5 @@
 import { LOCKFILE_VERSION, WANTED_LOCKFILE } from '@pnpm/constants'
+import PnpmError from '@pnpm/error'
 import {
   readCurrentLockfile,
   readWantedLockfile,
@@ -138,3 +139,46 @@ test('write does not use yaml anchors/aliases', async () => {
   expect(lockfileContent).not.toMatch('&')
   expect(lockfileContent).not.toMatch('*')
 })
+
+test('writeLockfiles() fails with meaningful error, when an invalid lockfile object is passed in', async () => {
+  const projectPath = tempy.directory()
+  const wantedLockfile = {
+    importers: {
+      '.': {
+        dependencies: {
+          'is-negative': '1.0.0',
+          'is-positive': '1.0.0',
+        },
+        // eslint-disable-next-line
+        specifiers: undefined as any,
+      },
+    },
+    lockfileVersion: LOCKFILE_VERSION,
+    packages: {
+      '/is-negative/1.0.0': {
+        dependencies: {
+          'is-positive': '2.0.0',
+        },
+        resolution: {
+          integrity: 'sha1-ChbBDewTLAqLCzb793Fo5VDvg/g=',
+        },
+      },
+      '/is-positive/1.0.0': {
+        resolution: {
+          integrity: 'sha1-ChbBDewTLAqLCzb793Fo5VDvg/g=',
+        },
+      },
+      '/is-positive/2.0.0': {
+        resolution: {
+          integrity: 'sha1-ChbBDewTLAqLCzb793Fo5VDvg/g=',
+        },
+      },
+    },
+  }
+  expect(() => writeLockfiles({
+    currentLockfile: wantedLockfile,
+    currentLockfileDir: projectPath,
+    wantedLockfile,
+    wantedLockfileDir: projectPath,
+  })).toThrow(new PnpmError('LOCKFILE_STRINGIFY', 'Failed to stringify the lockfile object. Undefined value at: importers[.].specifiers'))
+})