errors: Use `errors.As()` for type assertion

Currently for type assertion of errors, we use the `err.(<Interface>)`
form. This works, but is not compatible with wrapped errors. So let's
use `errors.As()` instead.

11 files changed, 48 insertions, 27 deletions

diff --git a/cmd/gitaly/main_test.go b/cmd/gitaly/main_test.go
index b649c10aa..339d7cbd6 100644
--- a/cmd/gitaly/main_test.go
+++ b/cmd/gitaly/main_test.go
@@ -2,6 +2,7 @@ package main
 
 import (
 	"bytes"
+	"errors"
 	"os/exec"
 	"testing"
 
@@ -63,8 +64,9 @@ func TestGitalyCLI(t *testing.T) {
 			err := cmd.Run()
 
 			exitCode := 0
-			if err != nil {
-				exitCode = err.(*exec.ExitError).ExitCode()
+			var exitErr *exec.ExitError
+			if errors.As(err, &exitErr) {
+				exitCode = exitErr.ExitCode()
 			}
 
 			assert.Equal(t, tc.exitCode, exitCode)
diff --git a/internal/backup/sink_test.go b/internal/backup/sink_test.go
index 9ff6f3f8a..5eb337147 100644
--- a/internal/backup/sink_test.go
+++ b/internal/backup/sink_test.go
@@ -2,6 +2,7 @@ package backup
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -24,8 +25,8 @@ func TestResolveSink(t *testing.T) {
 			sssink, ok := sink.(*StorageServiceSink)
 			require.True(t, ok)
 			_, err := sssink.bucket.List(nil).Next(ctx)
-			ierr, ok := err.(interface{ Unwrap() error })
-			require.True(t, ok)
+			var ierr interface{ Unwrap() error }
+			require.True(t, errors.As(err, &ierr))
 			terr := ierr.Unwrap()
 			require.Contains(t, terr.Error(), expErrMsg)
 		}
diff --git a/internal/cli/praefect/subcmd_track_repositories.go b/internal/cli/praefect/subcmd_track_repositories.go
index 9de4ddfbf..bde162108 100644
--- a/internal/cli/praefect/subcmd_track_repositories.go
+++ b/internal/cli/praefect/subcmd_track_repositories.go
@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -215,10 +216,11 @@ func printInvalidRequests(w io.Writer, repoErrs []invalidRequest, pathLines map[
 	for _, l := range repoErrs {
 		fmt.Fprintf(w, "  line %v, relative_path: %q, replica_path: %q\n", l.line, l.relativePath, l.replicaPath)
 		for _, err := range l.errs {
-			if dup, ok := err.(*dupPathError); ok {
+			var dupPathErr *dupPathError
+			if errors.As(err, &dupPathErr) {
 				// The complete set of duplicate reqNums won't be known until input is
 				// fully processed, fetch them now.
-				err = &dupPathError{path: dup.path, reqNums: pathLines[dup.path]}
+				err = &dupPathError{path: dupPathErr.path, reqNums: pathLines[dupPathErr.path]}
 			}
 			fmt.Fprintf(w, "    %v\n", err)
 		}
diff --git a/internal/git/gittest/command.go b/internal/git/gittest/command.go
index 30d276961..c5eef143c 100644
--- a/internal/git/gittest/command.go
+++ b/internal/git/gittest/command.go
@@ -2,6 +2,7 @@ package gittest
 
 import (
 	"context"
+	"errors"
 	"io"
 	"os"
 	"os/exec"
@@ -67,11 +68,12 @@ func ExecOpts(tb testing.TB, cfg config.Cfg, execCfg ExecConfig, args ...string)
 
 func handleExecErr(tb testing.TB, cfg config.Cfg, execCfg ExecConfig, args []string, err error) {
 	var stderr []byte
-	if ee, ok := err.(*exec.ExitError); ok {
-		if execCfg.ExpectedExitCode == ee.ExitCode() {
+	var exitErr *exec.ExitError
+	if errors.As(err, &exitErr) {
+		if execCfg.ExpectedExitCode == exitErr.ExitCode() {
 			return
 		}
-		stderr = ee.Stderr
+		stderr = exitErr.Stderr
 	}
 	tb.Log(cfg.Git.BinPath, args)
 	if len(stderr) > 0 {
diff --git a/internal/git/objectpool/disconnect_test.go b/internal/git/objectpool/disconnect_test.go
index ff1b0f0d0..6774c9dfc 100644
--- a/internal/git/objectpool/disconnect_test.go
+++ b/internal/git/objectpool/disconnect_test.go
@@ -431,9 +431,11 @@ func TestRemoveAlternatesIfOk(t *testing.T) {
 		altBackup := altPath + ".backup"
 		err = removeAlternatesIfOk(ctx, repo, altPath, altBackup, logger, nil)
 		require.Error(t, err, "removeAlternatesIfOk should fail")
-		require.IsType(t, &connectivityError{}, err, "error must be because of connectivity check")
-		connectivityErr := err.(*connectivityError)
-		require.IsType(t, &exec.ExitError{}, connectivityErr.error, "error must be because of fsck")
+
+		var connectivityErr *connectivityError
+		require.True(t, errors.As(err, &connectivityErr), "error must be because of connectivity check")
+		var exitError *exec.ExitError
+		require.True(t, errors.As(connectivityErr.error, &exitError), "error must be because of fsck")
 
 		// We expect objects/info/alternates to have been restored when
 		// removeAlternatesIfOk returned.
diff --git a/internal/gitaly/service/cleanup/apply_bfg_object_map_stream.go b/internal/gitaly/service/cleanup/apply_bfg_object_map_stream.go
index 5ecf4967f..0c13d57eb 100644
--- a/internal/gitaly/service/cleanup/apply_bfg_object_map_stream.go
+++ b/internal/gitaly/service/cleanup/apply_bfg_object_map_stream.go
@@ -1,6 +1,7 @@
 package cleanup
 
 import (
+	"errors"
 	"io"
 
 	"gitlab.com/gitlab-org/gitaly/v16/internal/gitaly/storage"
@@ -52,7 +53,8 @@ func (s *server) ApplyBfgObjectMapStream(server gitalypb.CleanupService_ApplyBfg
 	}
 
 	if err := cleaner.applyObjectMap(ctx, reader.streamReader()); err != nil {
-		if invalidErr, ok := err.(errInvalidObjectMap); ok {
+		var invalidErr errInvalidObjectMap
+		if errors.As(err, &invalidErr) {
 			return structerr.NewInvalidArgument("%w", invalidErr)
 		}
 
diff --git a/internal/grpc/dnsresolver/resolver.go b/internal/grpc/dnsresolver/resolver.go
index 28396582b..df21fb198 100644
--- a/internal/grpc/dnsresolver/resolver.go
+++ b/internal/grpc/dnsresolver/resolver.go
@@ -2,6 +2,7 @@ package dnsresolver
 
 import (
 	"context"
+	"errors"
 	"net"
 	"sync"
 	"time"
@@ -131,7 +132,8 @@ func (d *dnsResolver) resolve() (*resolver.State, error) {
 //     Backoff).
 //   - Other errors should be suppressed (they may represent the absence of a TXT record).
 func handleDNSError(err error) error {
-	if dnsErr, ok := err.(*net.DNSError); ok && !dnsErr.IsTimeout && !dnsErr.IsTemporary {
+	var dnsErr *net.DNSError
+	if errors.As(err, &dnsErr) && !dnsErr.IsTimeout && !dnsErr.IsTemporary {
 		return nil
 	}
 
diff --git a/internal/streamcache/cache_test.go b/internal/streamcache/cache_test.go
index f3a1bd57b..c8fdc82a6 100644
--- a/internal/streamcache/cache_test.go
+++ b/internal/streamcache/cache_test.go
@@ -365,8 +365,10 @@ func TestCache_unWriteableFile(t *testing.T) {
 		_, err := io.WriteString(w, "hello")
 		return err
 	})
-	require.IsType(t, &os.PathError{}, err)
-	require.Equal(t, "write", err.(*os.PathError).Op)
+
+	var pathErr *os.PathError
+	require.True(t, errors.As(err, &pathErr))
+	require.Equal(t, "write", pathErr.Op)
 }
 
 func TestCache_unCloseableFile(t *testing.T) {
@@ -385,8 +387,10 @@ func TestCache_unCloseableFile(t *testing.T) {
 	}
 
 	_, _, err := c.Fetch(ctx, "key", io.Discard, func(w io.Writer) error { return nil })
-	require.IsType(t, &os.PathError{}, err)
-	require.Equal(t, "close", err.(*os.PathError).Op)
+
+	var pathErr *os.PathError
+	require.True(t, errors.As(err, &pathErr))
+	require.Equal(t, "close", pathErr.Op)
 }
 
 func TestCache_cannotOpenFileForReading(t *testing.T) {
@@ -406,8 +410,9 @@ func TestCache_cannotOpenFileForReading(t *testing.T) {
 
 	_, _, err := c.Fetch(ctx, "key", io.Discard, func(w io.Writer) error { return nil })
 	err = errors.Unwrap(err)
-	require.IsType(t, &os.PathError{}, err)
-	require.Equal(t, "open", err.(*os.PathError).Op)
+	var pathErr *os.PathError
+	require.True(t, errors.As(err, &pathErr))
+	require.Equal(t, "open", pathErr.Op)
 }
 
 func TestWaiter(t *testing.T) {
diff --git a/internal/structerr/error.go b/internal/structerr/error.go
index e0c5dd0c7..70cc9a58e 100644
--- a/internal/structerr/error.go
+++ b/internal/structerr/error.go
@@ -262,7 +262,8 @@ func (e Error) GRPCStatus() *status.Status {
 func (e Error) errorChain() []Error {
 	var result []Error
 	for err := error(e); err != nil; err = errors.Unwrap(err) {
-		if structErr, ok := err.(Error); ok {
+		var structErr Error
+		if errors.As(err, &structErr) {
 			result = append(result, structErr)
 		}
 	}
diff --git a/internal/testhelper/leakage.go b/internal/testhelper/leakage.go
index 7a9c4006a..5aef11923 100644
--- a/internal/testhelper/leakage.go
+++ b/internal/testhelper/leakage.go
@@ -1,6 +1,7 @@
 package testhelper
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"os/exec"
@@ -81,13 +82,13 @@ func mustFindNoRunningChildProcess() error {
 		return fmt.Errorf("found running child processes %s:\n%s", pidsComma, psOut)
 	}
 
-	exitError, ok := err.(*exec.ExitError)
-	if !ok {
+	var exitErr *exec.ExitError
+	if !errors.As(err, &exitErr) {
 		//nolint:gitaly-linters
 		return fmt.Errorf("expected ExitError, got %T", err)
 	}
 
-	if exitError.ExitCode() == 1 {
+	if exitErr.ExitCode() == 1 {
 		return nil
 	}
 
diff --git a/internal/testhelper/testhelper.go b/internal/testhelper/testhelper.go
index 6de813fb6..67905f67e 100644
--- a/internal/testhelper/testhelper.go
+++ b/internal/testhelper/testhelper.go
@@ -129,9 +129,10 @@ func MustRunCommand(tb testing.TB, stdin io.Reader, name string, args ...string)
 	}
 
 	output, err := cmd.Output()
-	if err != nil {
-		stderr := err.(*exec.ExitError).Stderr
-		require.NoError(tb, err, "%s %s: %s", name, args, stderr)
+
+	var exitErr *exec.ExitError
+	if errors.As(err, &exitErr) {
+		require.NoError(tb, err, "%s %s: %s", name, args, exitErr.Stderr)
 	}
 
 	return output