ref: Always use structured errors in FindTag RPC

With 453ac57fc (ref: Fix `Internal` errors in `FindTag()` when tag
doesn't exist, 2022-08-01) we have adapted the FindTag RPC to return a
`NotFound` error instead of an `Internal` one when the tag wasn't found
in order to clearly label this error condition as expected.

This code has been rolled out to production on August 2nd without any
observed negative fallout. Remove the feature flag guarding it.

Changelog: changed

3 files changed, 23 insertions, 48 deletions

diff --git a/internal/gitaly/service/ref/find_tag.go b/internal/gitaly/service/ref/find_tag.go
index b23b50b3e..a96e9db78 100644
--- a/internal/gitaly/service/ref/find_tag.go
+++ b/internal/gitaly/service/ref/find_tag.go
@@ -10,7 +10,6 @@ import (
 	"gitlab.com/gitlab-org/gitaly/v15/internal/git"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/git/catfile"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/helper"
-	"gitlab.com/gitlab-org/gitaly/v15/internal/metadata/featureflag"
 	"gitlab.com/gitlab-org/gitaly/v15/proto/go/gitalypb"
 )
 
@@ -95,25 +94,21 @@ func (s *server) findTag(ctx context.Context, repo git.RepositoryExecutor, tagNa
 			return nil, err
 		}
 	} else {
-		if featureflag.FindTagStructuredError.IsEnabled(ctx) {
-			detailedErr, err := helper.ErrWithDetails(
-				helper.ErrNotFoundf("tag does not exist"),
-				&gitalypb.FindTagError{
-					Error: &gitalypb.FindTagError_TagNotFound{
-						TagNotFound: &gitalypb.ReferenceNotFoundError{
-							ReferenceName: []byte(fmt.Sprintf("refs/tags/%s", tagName)),
-						},
+		detailedErr, err := helper.ErrWithDetails(
+			helper.ErrNotFoundf("tag does not exist"),
+			&gitalypb.FindTagError{
+				Error: &gitalypb.FindTagError_TagNotFound{
+					TagNotFound: &gitalypb.ReferenceNotFoundError{
+						ReferenceName: []byte(fmt.Sprintf("refs/tags/%s", tagName)),
 					},
 				},
-			)
-			if err != nil {
-				return nil, helper.ErrInternalf("generating detailed error: %w", err)
-			}
-
-			return nil, detailedErr
+			},
+		)
+		if err != nil {
+			return nil, helper.ErrInternalf("generating detailed error: %w", err)
 		}
 
-		return nil, errors.New("no tag found")
+		return nil, detailedErr
 	}
 
 	if err = tagCmd.Wait(); err != nil {
diff --git a/internal/gitaly/service/ref/find_tag_test.go b/internal/gitaly/service/ref/find_tag_test.go
index aeeaf9c56..9baebb4e3 100644
--- a/internal/gitaly/service/ref/find_tag_test.go
+++ b/internal/gitaly/service/ref/find_tag_test.go
@@ -3,7 +3,6 @@
 package ref
 
 import (
-	"context"
 	"fmt"
 	"strings"
 	"testing"
@@ -15,7 +14,6 @@ import (
 	"gitlab.com/gitlab-org/gitaly/v15/internal/git/localrepo"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/git/updateref"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/helper"
-	"gitlab.com/gitlab-org/gitaly/v15/internal/metadata/featureflag"
 	"gitlab.com/gitlab-org/gitaly/v15/internal/testhelper"
 	"gitlab.com/gitlab-org/gitaly/v15/proto/go/gitalypb"
 	"google.golang.org/grpc/codes"
@@ -263,12 +261,8 @@ func TestFindTag_nestedTag(t *testing.T) {
 
 func TestFindTag_notFound(t *testing.T) {
 	t.Parallel()
-	testhelper.NewFeatureSets(featureflag.FindTagStructuredError).Run(t, testFindTagNotFound)
-}
-
-func testFindTagNotFound(t *testing.T, ctx context.Context) {
-	t.Parallel()
 
+	ctx := testhelper.Context(t)
 	cfg, client := setupRefServiceWithoutRepo(t)
 	repoProto, _ := gittest.CreateRepository(ctx, t, cfg)
 
@@ -277,23 +271,19 @@ func testFindTagNotFound(t *testing.T, ctx context.Context) {
 		TagName:    []byte("does-not-exist"),
 	})
 	require.Nil(t, response)
-	if featureflag.FindTagStructuredError.IsEnabled(ctx) {
-		expectedErr, errGeneratingDetails := helper.ErrWithDetails(
-			helper.ErrNotFoundf("tag does not exist"),
-			&gitalypb.FindTagError{
-				Error: &gitalypb.FindTagError_TagNotFound{
-					TagNotFound: &gitalypb.ReferenceNotFoundError{
-						ReferenceName: []byte("refs/tags/does-not-exist"),
-					},
+
+	expectedErr, errGeneratingDetails := helper.ErrWithDetails(
+		helper.ErrNotFoundf("tag does not exist"),
+		&gitalypb.FindTagError{
+			Error: &gitalypb.FindTagError_TagNotFound{
+				TagNotFound: &gitalypb.ReferenceNotFoundError{
+					ReferenceName: []byte("refs/tags/does-not-exist"),
 				},
 			},
-		)
-		require.NoError(t, errGeneratingDetails)
-
-		testhelper.RequireGrpcError(t, expectedErr, err)
-	} else {
-		testhelper.RequireGrpcError(t, helper.ErrInternalf("no tag found"), err)
-	}
+		},
+	)
+	require.NoError(t, errGeneratingDetails)
+	testhelper.RequireGrpcError(t, expectedErr, err)
 }
 
 func TestFindTag_invalidRequest(t *testing.T) {
diff --git a/internal/metadata/featureflag/ff_find_tag_structured_error.go b/internal/metadata/featureflag/ff_find_tag_structured_error.go
deleted file mode 100644
index 900f1eefc..000000000
--- a/internal/metadata/featureflag/ff_find_tag_structured_error.go
+++ /dev/null
@@ -1,10 +0,0 @@
-package featureflag
-
-// FindTagStructuredError enables the use of structured errors for the FindTag RPC in case the tag
-// could not be found.
-var FindTagStructuredError = NewFeatureFlag(
-	"find_tag_structured_error",
-	"v15.3.0",
-	"https://gitlab.com/gitlab-org/gitaly/-/issues/4398",
-	false,
-)