cmd/go/internal/modfetch/codehost: remove invariantly-empty return value from Repo.ReadZip

Previously, codehost.Repo.ReadZip returned an 'actualSubdir' value
that was the empty string in all current implementations.

Updates #26092

Change-Id: I6708dd0f13ba88bcf1a1fb405e9d818fd6f9197e
Reviewed-on: https://go-review.googlesource.com/c/go/+/203277
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

src/cmd/go/internal/modfetch/codehost/codehost.go

@@ -73,11 +73,10 @@ type Repo interface {
 	// ReadZip downloads a zip file for the subdir subdirectory
 	// of the given revision to a new file in a given temporary directory.
 	// It should refuse to read more than maxSize bytes.
-	// It returns a ReadCloser for a streamed copy of the zip file,
-	// along with the actual subdirectory (possibly shorter than subdir)
-	// contained in the zip file. All files in the zip file are expected to be
+	// It returns a ReadCloser for a streamed copy of the zip file.
+	// All files in the zip file are expected to be
 	// nested in a single top-level directory, whose name is not specified.
-	ReadZip(rev, subdir string, maxSize int64) (zip io.ReadCloser, actualSubdir string, err error)
+	ReadZip(rev, subdir string, maxSize int64) (zip io.ReadCloser, err error)
 
 	// RecentTag returns the most recent tag on rev or one of its predecessors
 	// with the given prefix and major version.

src/cmd/go/internal/modfetch/codehost/git.go

@@ -795,7 +795,7 @@ func (r *gitRepo) DescendsFrom(rev, tag string) (bool, error) {
 	return false, err
 }
 
-func (r *gitRepo) ReadZip(rev, subdir string, maxSize int64) (zip io.ReadCloser, actualSubdir string, err error) {
+func (r *gitRepo) ReadZip(rev, subdir string, maxSize int64) (zip io.ReadCloser, err error) {
 	// TODO: Use maxSize or drop it.
 	args := []string{}
 	if subdir != "" {
@@ -803,17 +803,17 @@ func (r *gitRepo) ReadZip(rev, subdir string, maxSize int64) (zip io.ReadCloser,
 	}
 	info, err := r.Stat(rev) // download rev into local git repo
 	if err != nil {
-		return nil, "", err
+		return nil, err
 	}
 
 	unlock, err := r.mu.Lock()
 	if err != nil {
-		return nil, "", err
+		return nil, err
 	}
 	defer unlock()
 
 	if err := ensureGitAttributes(r.dir); err != nil {
-		return nil, "", err
+		return nil, err
 	}
 
 	// Incredibly, git produces different archives depending on whether
@@ -824,12 +824,12 @@ func (r *gitRepo) ReadZip(rev, subdir string, maxSize int64) (zip io.ReadCloser,
 	archive, err := Run(r.dir, "git", "-c", "core.autocrlf=input", "-c", "core.eol=lf", "archive", "--format=zip", "--prefix=prefix/", info.Name, args)
 	if err != nil {
 		if bytes.Contains(err.(*RunError).Stderr, []byte("did not match any files")) {
-			return nil, "", os.ErrNotExist
+			return nil, os.ErrNotExist
 		}
-		return nil, "", err
+		return nil, err
 	}
 
-	return ioutil.NopCloser(bytes.NewReader(archive)), "", nil
+	return ioutil.NopCloser(bytes.NewReader(archive)), nil
 }
 
 // ensureGitAttributes makes sure export-subst and export-ignore features are

src/cmd/go/internal/modfetch/codehost/git_test.go

@@ -246,12 +246,11 @@ func TestReadFile(t *testing.T) {
 }
 
 var readZipTests = []struct {
-	repo         string
-	rev          string
-	subdir       string
-	actualSubdir string
-	err          string
-	files        map[string]uint64
+	repo   string
+	rev    string
+	subdir string
+	err    string
+	files  map[string]uint64
 }{
 	{
 		repo:   gitrepo1,
@@ -408,7 +407,7 @@ func TestReadZip(t *testing.T) {
 			if err != nil {
 				t.Fatal(err)
 			}
-			rc, actualSubdir, err := r.ReadZip(tt.rev, tt.subdir, 100000)
+			rc, err := r.ReadZip(tt.rev, tt.subdir, 100000)
 			if err != nil {
 				if tt.err == "" {
 					t.Fatalf("ReadZip: unexpected error %v", err)
@@ -425,9 +424,6 @@ func TestReadZip(t *testing.T) {
 			if tt.err != "" {
 				t.Fatalf("ReadZip: no error, wanted %v", tt.err)
 			}
-			if actualSubdir != tt.actualSubdir {
-				t.Fatalf("ReadZip: actualSubdir = %q, want %q", actualSubdir, tt.actualSubdir)
-			}
 			zipdata, err := ioutil.ReadAll(rc)
 			if err != nil {
 				t.Fatal(err)

src/cmd/go/internal/modfetch/codehost/shell.go

@@ -109,7 +109,7 @@ func main() {
 			if subdir == "-" {
 				subdir = ""
 			}
-			rc, _, err := repo.ReadZip(f[1], subdir, 10<<20)
+			rc, err := repo.ReadZip(f[1], subdir, 10<<20)
 			if err != nil {
 				fmt.Fprintf(os.Stderr, "?%s\n", err)
 				continue

src/cmd/go/internal/modfetch/codehost/vcs.go

@@ -417,14 +417,14 @@ func (r *vcsRepo) DescendsFrom(rev, tag string) (bool, error) {
 	return false, vcsErrorf("DescendsFrom not implemented")
 }
 
-func (r *vcsRepo) ReadZip(rev, subdir string, maxSize int64) (zip io.ReadCloser, actualSubdir string, err error) {
+func (r *vcsRepo) ReadZip(rev, subdir string, maxSize int64) (zip io.ReadCloser, err error) {
 	if r.cmd.readZip == nil {
-		return nil, "", vcsErrorf("ReadZip not implemented for %s", r.cmd.vcs)
+		return nil, vcsErrorf("ReadZip not implemented for %s", r.cmd.vcs)
 	}
 
 	unlock, err := r.mu.Lock()
 	if err != nil {
-		return nil, "", err
+		return nil, err
 	}
 	defer unlock()
 
@@ -433,7 +433,7 @@ func (r *vcsRepo) ReadZip(rev, subdir string, maxSize int64) (zip io.ReadCloser,
 	}
 	f, err := ioutil.TempFile("", "go-readzip-*.zip")
 	if err != nil {
-		return nil, "", err
+		return nil, err
 	}
 	if r.cmd.vcs == "fossil" {
 		// If you run
@@ -454,9 +454,9 @@ func (r *vcsRepo) ReadZip(rev, subdir string, maxSize int64) (zip io.ReadCloser,
 	if err != nil {
 		f.Close()
 		os.Remove(f.Name())
-		return nil, "", err
+		return nil, err
 	}
-	return &deleteCloser{f}, "", nil
+	return &deleteCloser{f}, nil
 }
 
 // deleteCloser is a file that gets deleted on Close.

src/cmd/go/internal/modfetch/coderepo.go

@@ -780,19 +780,16 @@ func (r *codeRepo) Zip(dst io.Writer, version string) error {
 		}
 	}
 
-	rev, dir, _, err := r.findDir(version)
+	rev, subdir, _, err := r.findDir(version)
 	if err != nil {
 		return err
 	}
-	dl, actualDir, err := r.code.ReadZip(rev, dir, codehost.MaxZipFile)
+	dl, err := r.code.ReadZip(rev, subdir, codehost.MaxZipFile)
 	if err != nil {
 		return err
 	}
 	defer dl.Close()
-	if actualDir != "" && !hasPathPrefix(dir, actualDir) {
-		return fmt.Errorf("internal error: downloading %v %v: dir=%q but actualDir=%q", r.modPath, rev, dir, actualDir)
-	}
-	subdir := strings.Trim(strings.TrimPrefix(dir, actualDir), "/")
+	subdir = strings.Trim(subdir, "/")
 
 	// Spool to local file.
 	f, err := ioutil.TempFile("", "go-codehost-")