localrepo: Add ReadObjectInfo helper

Sometimes it's useful to quickly look up an object's info based on a
revision (which can include a path).

2 files changed, 62 insertions, 0 deletions

diff --git a/internal/git/localrepo/objects.go b/internal/git/localrepo/objects.go
index c9fb2345b..7586886af 100644
--- a/internal/git/localrepo/objects.go
+++ b/internal/git/localrepo/objects.go
@@ -185,6 +185,25 @@ type InvalidObjectError string
 
 func (err InvalidObjectError) Error() string { return fmt.Sprintf("invalid object %q", string(err)) }
 
+// ReadObjectInfo attempts to read the object info based on a revision.
+func (repo *Repo) ReadObjectInfo(ctx context.Context, rev git.Revision) (*catfile.ObjectInfo, error) {
+	infoReader, cleanup, err := repo.catfileCache.ObjectInfoReader(ctx, repo)
+	if err != nil {
+		return nil, fmt.Errorf("getting object info reader: %w", err)
+	}
+	defer cleanup()
+
+	objectInfo, err := infoReader.Info(ctx, rev)
+	if err != nil {
+		if catfile.IsNotFound(err) {
+			return nil, InvalidObjectError(rev)
+		}
+		return nil, fmt.Errorf("getting object info %w", err)
+	}
+
+	return objectInfo, nil
+}
+
 // ReadObject reads an object from the repository's object database. InvalidObjectError
 // is returned if the oid does not refer to a valid object.
 func (repo *Repo) ReadObject(ctx context.Context, oid git.ObjectID) ([]byte, error) {
diff --git a/internal/git/localrepo/objects_test.go b/internal/git/localrepo/objects_test.go
index c57c66c1b..107ab1f92 100644
--- a/internal/git/localrepo/objects_test.go
+++ b/internal/git/localrepo/objects_test.go
@@ -280,6 +280,49 @@ func testRepoReadObject(t *testing.T, ctx context.Context) {
 	}
 }
 
+func TestRepoReadObjectInfo(t *testing.T) {
+	t.Parallel()
+
+	ctx := testhelper.Context(t)
+	cfg, repo, repoPath := setupRepo(t)
+	blobID := gittest.WriteBlob(t, cfg, repoPath, []byte("content"))
+	objectHash, err := repo.ObjectHash(ctx)
+	require.NoError(t, err)
+
+	for _, tc := range []struct {
+		desc               string
+		oid                git.ObjectID
+		content            string
+		expectedErr        error
+		expectedObjectInfo catfile.ObjectInfo
+	}{
+		{
+			desc:        "missing object",
+			oid:         git.ObjectID("abcdefg"),
+			expectedErr: InvalidObjectError("abcdefg"),
+		},
+		{
+			desc:    "valid object",
+			oid:     blobID,
+			content: "content",
+			expectedObjectInfo: catfile.ObjectInfo{
+				Oid:    blobID,
+				Type:   "blob",
+				Size:   7,
+				Format: objectHash.Format,
+			},
+		},
+	} {
+		t.Run(tc.desc, func(t *testing.T) {
+			info, err := repo.ReadObjectInfo(ctx, git.Revision(tc.oid))
+			require.Equal(t, tc.expectedErr, err)
+			if tc.expectedErr == nil {
+				require.Equal(t, tc.expectedObjectInfo, *info)
+			}
+		})
+	}
+}
+
 func TestRepo_ReadObject_catfileCount(t *testing.T) {
 	t.Parallel()