pkg/osutil: make VerboseError nest other errors

After this change it fits more naturally into the Go's error
functionality.

5 files changed, 13 insertions, 21 deletions

diff --git a/pkg/bisect/bisect.go b/pkg/bisect/bisect.go
index c4b2ebf50..55a5d44f7 100644
--- a/pkg/bisect/bisect.go
+++ b/pkg/bisect/bisect.go
@@ -658,7 +658,7 @@ func (env *env) test() (*testResult, error) {
 		var verr *osutil.VerboseError
 		var kerr *build.KernelError
 		if errors.As(err, &verr) {
-			errInfo += verr.Title
+			errInfo += verr.Error()
 			env.saveDebugFile(current.Hash, 0, verr.Output)
 		} else if errors.As(err, &kerr) {
 			errInfo += string(kerr.Report)
diff --git a/pkg/build/freebsd.go b/pkg/build/freebsd.go
index 5de09738a..4b403d587 100644
--- a/pkg/build/freebsd.go
+++ b/pkg/build/freebsd.go
@@ -54,7 +54,7 @@ options 	DIAGNOSTIC
 		// because FreeBSD's build doesn't correctly order the two
 		// targets. Its output is useful for debugging though, so
 		// include it here.
-		return ImageDetails{}, osutil.PrependContext(string(output), err)
+		return ImageDetails{}, fmt.Errorf("%s: %w", string(output), err)
 	}
 
 	kernelObjDir := filepath.Join(objPrefix, params.KernelDir,
diff --git a/pkg/cover/report_test.go b/pkg/cover/report_test.go
index 96b634cc6..c3d3231fb 100644
--- a/pkg/cover/report_test.go
+++ b/pkg/cover/report_test.go
@@ -11,6 +11,7 @@ import (
 	"bytes"
 	"encoding/csv"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -283,7 +284,8 @@ func buildTestBinary(t *testing.T, target *targets.Target, test *Test, dir strin
 	}
 	if _, err := osutil.RunCmd(time.Hour, "", target.CCompiler, ldflags...); err != nil {
 		// Arm linker in the env image has a bug when linking a clang-produced files.
-		if regexp.MustCompile(`arm-linux-gnueabi.* assertion fail`).MatchString(err.Error()) {
+		var vErr *osutil.VerboseError
+		if errors.As(err, &vErr) && regexp.MustCompile(`arm-linux-gnueabi.* assertion fail`).Match(vErr.Output) {
 			t.Skipf("skipping test, broken arm linker (%v)", err)
 		}
 		t.Fatal(err)
diff --git a/pkg/instance/instance.go b/pkg/instance/instance.go
index 51802acf9..b4460e3ab 100644
--- a/pkg/instance/instance.go
+++ b/pkg/instance/instance.go
@@ -568,7 +568,7 @@ func RunSmokeTest(cfg *mgrconfig.Config) (*report.Report, error) {
 			var verboseErr *osutil.VerboseError
 			if errors.As(retErr, &verboseErr) {
 				// Include more details into the report.
-				prefix := fmt.Sprintf("%s, exit code %d\n\n", verboseErr.Title, verboseErr.ExitCode)
+				prefix := fmt.Sprintf("%s, exit code %d\n\n", verboseErr, verboseErr.ExitCode)
 				output = append([]byte(prefix), output...)
 			}
 			rep := &report.Report{
diff --git a/pkg/osutil/osutil.go b/pkg/osutil/osutil.go
index d16a76cb7..1379e8c23 100644
--- a/pkg/osutil/osutil.go
+++ b/pkg/osutil/osutil.go
@@ -65,9 +65,9 @@ func Run(timeout time.Duration, cmd *exec.Cmd) ([]byte, error) {
 	err := cmd.Wait()
 	close(done)
 	if err != nil {
-		text := fmt.Sprintf("failed to run %q: %v", cmd.Args, err)
+		retErr := fmt.Errorf("failed to run %q: %w", cmd.Args, err)
 		if <-timedout {
-			text = fmt.Sprintf("timedout after %v %q", timeout, cmd.Args)
+			retErr = fmt.Errorf("timedout after %v %q", timeout, cmd.Args)
 		}
 		exitCode := cmd.ProcessState.ExitCode()
 		var exitErr *exec.ExitError
@@ -77,7 +77,7 @@ func Run(timeout time.Duration, cmd *exec.Cmd) ([]byte, error) {
 			}
 		}
 		return output.Bytes(), &VerboseError{
-			Title:    text,
+			Err:      retErr,
 			Output:   output.Bytes(),
 			ExitCode: exitCode,
 		}
@@ -111,27 +111,17 @@ func GraciousCommand(bin string, args ...string) *exec.Cmd {
 }
 
 type VerboseError struct {
-	Title    string
+	Err      error
 	Output   []byte
 	ExitCode int
 }
 
 func (err *VerboseError) Error() string {
-	if len(err.Output) == 0 {
-		return err.Title
-	}
-	return fmt.Sprintf("%v\n%s", err.Title, err.Output)
+	return err.Err.Error()
 }
 
-func PrependContext(ctx string, err error) error {
-	var verboseError *VerboseError
-	switch {
-	case errors.As(err, &verboseError):
-		verboseError.Title = fmt.Sprintf("%v: %v", ctx, verboseError.Title)
-		return verboseError
-	default:
-		return fmt.Errorf("%v: %w", ctx, err)
-	}
+func (err *VerboseError) Unwrap() error {
+	return err.Err
 }
 
 func IsDir(name string) bool {