Keep temporary directory in case of failure

cmd/mkuimage/main.go

@@ -18,6 +18,7 @@
 	"github.com/dustin/go-humanize"
 	"github.com/u-root/gobusybox/src/pkg/golang"
 	"github.com/u-root/mkuimage/uimage"
+	"github.com/u-root/mkuimage/uimage/builder"
 	"github.com/u-root/mkuimage/uimage/uflags"
 	"github.com/u-root/uio/llog"
 )
@@ -137,19 +138,20 @@
 			v, recommendedVersions, recommendedVersions[0])
 	}
 
+	keepTempDir := f.KeepTempDir
 	if f.TempDir == "" {
 		var err error
 		f.TempDir, err = os.MkdirTemp("", "u-root")
 		if err != nil {
 			return err
 		}
-		if f.KeepTempDir {
-			defer func() {
+		defer func() {
+			if keepTempDir {
 				l.Infof("Keeping temp dir %s", f.TempDir)
-			}()
-		} else {
-			defer os.RemoveAll(f.TempDir)
-		}
+			} else {
+				os.RemoveAll(f.TempDir)
+			}
+		}()
 	} else if _, err := os.Stat(f.TempDir); os.IsNotExist(err) {
 		if err := os.MkdirAll(f.TempDir, 0o755); err != nil {
 			return fmt.Errorf("temporary directory %q did not exist; tried to mkdir but failed: %v", f.TempDir, err)
@@ -166,5 +168,11 @@
 	if err != nil {
 		return err
 	}
-	return uimage.Create(l, append(m, more...)...)
+
+	err = uimage.Create(l, append(m, more...)...)
+	if errors.Is(err, builder.ErrBusyboxFailed) {
+		l.Errorf("Preserving temp dir due to busybox build error")
+		keepTempDir = true
+	}
+	return err
 }

uimage/builder/builder.go

@@ -24,6 +24,7 @@ var (
 
 // Possible build errors.
 var (
+	ErrBusyboxFailed  = errors.New("gobusybox build failed")
 	ErrEnvMissing     = errors.New("must specify Go build environment")
 	ErrTempDirMissing = errors.New("must supply temporary directory for build")
 	ErrNoGoFiles      = errors.New("could not find package directory")

uimage/builder/gbb.go

@@ -80,12 +80,12 @@
 		var errGopath *bb.ErrGopathBuild
 		var errGomod *bb.ErrModuleBuild
 		if errors.As(err, &errGopath) {
-			return fmt.Errorf("preserving bb generated source directory at %s due to error. To reproduce build, `cd %s` and `GO111MODULE=off GOPATH=%s go build`: %w", opts.TempDir, errGopath.CmdDir, errGopath.GOPATH, err)
+			return fmt.Errorf("%w: to reproduce build, `cd %s` and `GO111MODULE=off GOPATH=%s go build`: %w", ErrBusyboxFailed, errGopath.CmdDir, errGopath.GOPATH, err)
 		}
 		if errors.As(err, &errGomod) {
-			return fmt.Errorf("preserving bb generated source directory at %s due to error. To debug build, `cd %s` and use `go build` to build, or `go mod [why|tidy|graph]` to debug dependencies, or `go list -m all` to list all dependency versions:\n%w", opts.TempDir, errGomod.CmdDir, err)
+			return fmt.Errorf("%w: to debug build, `cd %s` and use `go build` to build, or `go mod [why|tidy|graph]` to debug dependencies, or `go list -m all` to list all dependency versions:\n%w", ErrBusyboxFailed, errGomod.CmdDir, err)
 		}
-		return fmt.Errorf("preserving bb generated source directory at %s due to error:\n%w", opts.TempDir, err)
+		return fmt.Errorf("%w: %w", ErrBusyboxFailed, err)
 	}
 
 	if err := af.AddFile(bbPath, "bbin/bb"); err != nil {

uimage/uimage.go

@@ -647,7 +647,7 @@
 			BinaryDir: cmds.TargetDir(),
 		}
 		if err := cmds.Builder.Build(l, files, bOpts); err != nil {
-			return fmt.Errorf("error building: %v", err)
+			return fmt.Errorf("error building: %w", err)
 		}
 	}