[backend/filestate] Don't unwrap go-cloud errors (#8455)

* Don't unwrap go-cloud errors

* Remove unused func

* Add changelog entry

Co-authored-by: Ian Wahbe <ian@wahbe.com>

CHANGELOG_PENDING.md

@@ -16,3 +16,6 @@
 
 - [codegen/typescript] - Respect default values in Pulumi object types.
   [#8400](https://github.com/pulumi/pulumi/pull/8400)
+
+- [cli] - Catch expected errors in filestate backend stacks.
+  [#8455](https://github.com/pulumi/pulumi/pull/8455)

pkg/backend/filestate/backend.go

@@ -323,7 +323,7 @@ func (b *localBackend) GetStack(ctx context.Context, stackRef backend.StackRefer
 	snapshot, path, err := b.getStack(stackName)
 
 	switch {
-	case gcerrors.Code(drillError(err)) == gcerrors.NotFound:
+	case gcerrors.Code(err) == gcerrors.NotFound:
 		return nil, nil
 	case err != nil:
 		return nil, err
@@ -882,12 +882,3 @@ func (b *localBackend) UpdateStackTags(ctx context.Context,
 	// The local backend does not currently persist tags.
 	return errors.New("stack tags not supported in --local mode")
 }
-
-// Returns the original error in the chain. If `err` is nil, nil is returned.
-func drillError(err error) error {
-	e := err
-	for errors.Unwrap(e) != nil {
-		e = errors.Unwrap(e)
-	}
-	return e
-}

pkg/backend/filestate/backend_test.go

@@ -187,3 +187,20 @@ func TestListStacksWithMultiplePassphrases(t *testing.T) {
 	}
 
 }
+
+func TestDrillError(t *testing.T) {
+	// Login to a temp dir filestate backend
+	tmpDir, err := ioutil.TempDir("", "filestatebackend")
+	assert.NoError(t, err)
+	b, err := New(cmdutil.Diag(), "file://"+filepath.ToSlash(tmpDir))
+	assert.NoError(t, err)
+	ctx := context.Background()
+
+	// Get a non-existent stack and expect a nil error because it won't be found.
+	stackRef, err := b.ParseStackReference("dev")
+	if err != nil {
+		t.Fatalf("unexpected error %v when parsing stack reference", err)
+	}
+	_, err = b.GetStack(ctx, stackRef)
+	assert.Nil(t, err)
+}

pkg/backend/filestate/state.go

@@ -323,7 +323,7 @@ func (b *localBackend) getHistory(name tokens.QName, pageSize int, page int) ([]
 	allFiles, err := listBucket(b.bucket, dir)
 	if err != nil {
 		// History doesn't exist until a stack has been updated.
-		if gcerrors.Code(drillError(err)) == gcerrors.NotFound {
+		if gcerrors.Code(err) == gcerrors.NotFound {
 			return nil, nil
 		}
 		return nil, err
@@ -391,7 +391,7 @@ func (b *localBackend) renameHistory(oldName tokens.QName, newName tokens.QName)
 	allFiles, err := listBucket(b.bucket, oldHistory)
 	if err != nil {
 		// if there's nothing there, we don't really need to do a rename.
-		if gcerrors.Code(drillError(err)) == gcerrors.NotFound {
+		if gcerrors.Code(err) == gcerrors.NotFound {
 			return nil
 		}
 		return err