Fix a bug in the SFTP backend that would cause an error when overwriting existing files

internal/adapters/ssh/backend_test.go

@@ -0,0 +1,125 @@
+package ssh
+
+import (
+	"errors"
+	"os"
+	"testing"
+
+	"github.com/pkg/sftp"
+)
+
+func TestRenamePromotedFileUsesPlainRenameWithoutOverwrite(t *testing.T) {
+	client := &recordingRenamer{}
+	if err := renamePromotedFile(client, "temp", "index.html", false); err != nil {
+		t.Fatalf("renamePromotedFile() error = %v", err)
+	}
+	if got, want := client.calls, []string{"rename temp index.html"}; !equalStrings(got, want) {
+		t.Fatalf("calls = %q, want %q", got, want)
+	}
+}
+
+func TestRenamePromotedFileUsesPosixRenameForOverwrite(t *testing.T) {
+	client := &recordingRenamer{}
+	if err := renamePromotedFile(client, "temp", "index.html", true); err != nil {
+		t.Fatalf("renamePromotedFile() error = %v", err)
+	}
+	if got, want := client.calls, []string{"posix temp index.html"}; !equalStrings(got, want) {
+		t.Fatalf("calls = %q, want %q", got, want)
+	}
+}
+
+func TestRenamePromotedFileFallsBackWhenReplaceRenameUnsupported(t *testing.T) {
+	for _, err := range []error{
+		sftp.ErrSSHFxOpUnsupported,
+		sftp.ErrSSHFxFailure,
+		&sftp.StatusError{Code: uint32(sftp.ErrSSHFxOpUnsupported)},
+		&sftp.StatusError{Code: uint32(sftp.ErrSSHFxFailure)},
+	} {
+		t.Run(err.Error(), func(t *testing.T) {
+			client := &recordingRenamer{posixErr: err}
+			if err := renamePromotedFile(client, "temp", "index.html", true); err != nil {
+				t.Fatalf("renamePromotedFile() error = %v", err)
+			}
+			want := []string{"posix temp index.html", "remove index.html", "rename temp index.html"}
+			if got := client.calls; !equalStrings(got, want) {
+				t.Fatalf("calls = %q, want %q", got, want)
+			}
+		})
+	}
+}
+
+func TestRenamePromotedFileIgnoresMissingTargetDuringFallback(t *testing.T) {
+	client := &recordingRenamer{
+		posixErr: sftp.ErrSSHFxOpUnsupported,
+		removeErr: &os.PathError{
+			Op:   "remove",
+			Path: "index.html",
+			Err:  os.ErrNotExist,
+		},
+	}
+	if err := renamePromotedFile(client, "temp", "index.html", true); err != nil {
+		t.Fatalf("renamePromotedFile() error = %v", err)
+	}
+	want := []string{"posix temp index.html", "remove index.html", "rename temp index.html"}
+	if got := client.calls; !equalStrings(got, want) {
+		t.Fatalf("calls = %q, want %q", got, want)
+	}
+}
+
+func TestRenamePromotedFileDoesNotFallbackForPermissionError(t *testing.T) {
+	client := &recordingRenamer{posixErr: sftp.ErrSSHFxPermissionDenied}
+	if err := renamePromotedFile(client, "temp", "index.html", true); !errors.Is(err, sftp.ErrSSHFxPermissionDenied) {
+		t.Fatalf("renamePromotedFile() error = %v, want permission denied", err)
+	}
+	if got, want := client.calls, []string{"posix temp index.html"}; !equalStrings(got, want) {
+		t.Fatalf("calls = %q, want %q", got, want)
+	}
+}
+
+func TestRenamePromotedFileReturnsRemoveFallbackError(t *testing.T) {
+	client := &recordingRenamer{
+		posixErr:  sftp.ErrSSHFxOpUnsupported,
+		removeErr: sftp.ErrSSHFxPermissionDenied,
+	}
+	if err := renamePromotedFile(client, "temp", "index.html", true); !errors.Is(err, sftp.ErrSSHFxPermissionDenied) {
+		t.Fatalf("renamePromotedFile() error = %v, want permission denied", err)
+	}
+	want := []string{"posix temp index.html", "remove index.html"}
+	if got := client.calls; !equalStrings(got, want) {
+		t.Fatalf("calls = %q, want %q", got, want)
+	}
+}
+
+type recordingRenamer struct {
+	calls     []string
+	posixErr  error
+	renameErr error
+	removeErr error
+}
+
+func (r *recordingRenamer) PosixRename(oldname, newname string) error {
+	r.calls = append(r.calls, "posix "+oldname+" "+newname)
+	return r.posixErr
+}
+
+func (r *recordingRenamer) Rename(oldname, newname string) error {
+	r.calls = append(r.calls, "rename "+oldname+" "+newname)
+	return r.renameErr
+}
+
+func (r *recordingRenamer) Remove(path string) error {
+	r.calls = append(r.calls, "remove "+path)
+	return r.removeErr
+}
+
+func equalStrings(a, b []string) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for index := range a {
+		if a[index] != b[index] {
+			return false
+		}
+	}
+	return true
+}