fix: propagate error cause when throwing PnpmError in @pnpm/npm-resolver (#10990)

* fix: show error cause when failing to read metadata

* fix: correct changeset package name and add cause assertion tests

- Fix changeset to reference @pnpm/resolving.npm-resolver (not @pnpm/npm-resolver)
- Add PnpmError cause unit tests in @pnpm/error
- Fix npm-resolver tests to actually verify cause on thrown errors
  (.toThrow() only checks message, not cause/hint/code properties)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Zoltan Kochan <z@kochan.io>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.changeset/deep-ads-hope.md

@@ -0,0 +1,5 @@
+---
+"@pnpm/resolving.npm-resolver": patch
+---
+
+When package metadata is malformed or can't be fetched, the error thrown will now show the originating error.

.changeset/stale-regions-like.md

@@ -0,0 +1,5 @@
+---
+"@pnpm/error": minor
+---
+
+The `PnpmError` class now accepts an optional `cause` argument.

core/error/src/index.ts

@@ -12,9 +12,10 @@ export class PnpmError extends Error {
     opts?: {
       attempts?: number
       hint?: string
+      cause?: unknown
     }
   ) {
-    super(message)
+    super(message, { cause: opts?.cause })
     this.code = code.startsWith('ERR_PNPM_') ? code : `ERR_PNPM_${code}`
     this.hint = opts?.hint
     this.attempts = opts?.attempts

core/error/test/index.ts

@@ -1,4 +1,22 @@
-import { FetchError } from '@pnpm/error'
+import { FetchError, PnpmError } from '@pnpm/error'
+
+test('PnpmError exposes cause when provided', () => {
+  const cause = new Error('original failure')
+  const error = new PnpmError('TEST_CODE', 'something went wrong', { cause })
+  expect(error.cause).toBe(cause)
+  expect(error.message).toBe('something went wrong')
+  expect(error.code).toBe('ERR_PNPM_TEST_CODE')
+})
+
+test('PnpmError cause is undefined when omitted', () => {
+  const error = new PnpmError('TEST_CODE', 'something went wrong')
+  expect(error.cause).toBeUndefined()
+})
+
+test('PnpmError cause works with non-Error values', () => {
+  const error = new PnpmError('TEST_CODE', 'something went wrong', { cause: 'string cause' })
+  expect(error.cause).toBe('string cause')
+})
 
 test('FetchError escapes auth tokens', () => {
   const error = new FetchError(

resolving/npm-resolver/src/fetch.ts

@@ -86,7 +86,7 @@ export async function fetchMetadataFromFromRegistry (
           timeout: fetchOpts.timeout,
         }) as RegistryResponse
       } catch (error: any) { // eslint-disable-line
-        reject(new PnpmError('META_FETCH_FAIL', `GET ${uri}: ${error.message as string}`, { attempts: attempt }))
+        reject(new PnpmError('META_FETCH_FAIL', `GET ${uri}: ${error.message as string}`, { attempts: attempt, cause: error }))
         return
       }
       if (response.status >= 400) {

resolving/npm-resolver/src/pickPackageFromMeta.ts

@@ -90,7 +90,7 @@ export function pickPackageFromMeta (
     }
     throw new PnpmError('MALFORMED_METADATA',
       `Received malformed metadata for "${spec.name}"`,
-      { hint: 'This might mean that the package was unpublished from the registry' }
+      { hint: 'This might mean that the package was unpublished from the registry', cause: err }
     )
   }
 }

resolving/npm-resolver/test/index.ts

@@ -865,8 +865,19 @@ test('error is thrown when registry not responding', async () => {
       default: notExistingRegistry,
     },
   })
-  await expect(resolveFromNpm({ alias: notExistingPackage, bareSpecifier: '1.0.0' }, {})).rejects
-    .toThrow(new PnpmError('META_FETCH_FAIL', `GET ${notExistingRegistry}/${notExistingPackage}: request to ${notExistingRegistry}/${notExistingPackage} failed, reason: getaddrinfo ENOTFOUND not-existing.pnpm.io`, { attempts: 1 }))
+
+  let thrown: any // eslint-disable-line
+  try {
+    await resolveFromNpm({ alias: notExistingPackage, bareSpecifier: '1.0.0' }, {})
+  } catch (err) {
+    thrown = err
+  }
+  expect(thrown).toBeTruthy()
+  expect(thrown.code).toBe('ERR_PNPM_META_FETCH_FAIL')
+  expect(thrown.message).toContain(`GET ${notExistingRegistry}/${notExistingPackage}:`)
+  expect(thrown.message).toContain('ENOTFOUND')
+  expect(thrown.cause).toBeTruthy()
+  expect(thrown.cause.code).toBe('ENOTFOUND')
 })
 
 test('extra info is shown if package has valid semver appended', async () => {
@@ -1961,10 +1972,18 @@ test('request to a package with no dist-tags', async () => {
     registries,
   })
 
-  await expect(resolveFromNpm({ alias: 'is-positive' }, {})).rejects
-    .toThrow(
-      new PnpmError('MALFORMED_METADATA', 'Received malformed metadata for "is-positive"')
-    )
+  let thrown: any // eslint-disable-line
+  try {
+    await resolveFromNpm({ alias: 'is-positive' }, {})
+  } catch (err) {
+    thrown = err
+  }
+  expect(thrown).toBeTruthy()
+  expect(thrown.code).toBe('ERR_PNPM_MALFORMED_METADATA')
+  expect(thrown.message).toBe('Received malformed metadata for "is-positive"')
+  expect(thrown.hint).toBe('This might mean that the package was unpublished from the registry')
+  expect(thrown.cause).toBeTruthy()
+  expect(thrown.cause.message).toContain("Cannot read properties of undefined (reading 'latest')")
 })
 
 test('resolveFromNpm() does not fail if the meta file contains no integrity information', async () => {