Merge lp:~sergiusens/goget-ubuntu-touch/ErrExec into lp:goget-ubuntu-touch

[Sergio Schvezov]

Better errors when executing commands in diskimage

[John Lenton (chipaca)]

I wonder how many times we're going to recreate this pattern before we make it part of our toolset.

review: Approve

=== modified file 'diskimage/common.go'
--- diskimage/common.go	2015-07-09 10:00:18 +0000
+++ diskimage/common.go	2015-07-10 17:13:52 +0000
@@ -343,13 +343,15 @@
 	}
 
 	for _, part := range img.parts {
-		if err := exec.Command("dmsetup", "clear", part.loop).Run(); err != nil {
-			return err
+		dmsetupCmd := []string{"dmsetup", "clear", part.loop}
+		if out, err := exec.Command(dmsetupCmd[0], dmsetupCmd[1:]...).CombinedOutput(); err != nil {
+			return &ErrExec{command: dmsetupCmd, output: out}
 		}
 	}
 
-	if err := exec.Command("kpartx", "-ds", img.location).Run(); err != nil {
-		return err
+	kpartxCmd := []string{"kpartx", "-ds", img.location}
+	if out, err := exec.Command(kpartxCmd[0], kpartxCmd[1:]...).CombinedOutput(); err != nil {
+		return &ErrExec{command: kpartxCmd, output: out}
 	}
 
 	unmapPartitions(img.parts)
@@ -377,7 +379,7 @@
 		dev := filepath.Join("/dev/mapper", part.loop)
 
 		if part.fs == fsFat32 {
-			cmd := []string{"-F", "32", "-n", string(part.label)}
+			cmd := []string{"mkfs.vfat", "-F", "32", "-n", string(part.label)}
 
 			size, err := sectorSize(dev)
 			if err != nil {
@@ -390,12 +392,13 @@
 
 			cmd = append(cmd, "-S", size, dev)
 
-			if out, err := exec.Command("mkfs.vfat", cmd...).CombinedOutput(); err != nil {
-				return fmt.Errorf("unable to create filesystem: %s", out)
+			if out, err := exec.Command(cmd[0], cmd[1:]...).CombinedOutput(); err != nil {
+				return &ErrExec{command: cmd, output: out}
 			}
 		} else {
-			if out, err := exec.Command("mkfs.ext4", "-F", "-L", string(part.label), dev).CombinedOutput(); err != nil {
-				return fmt.Errorf("unable to create filesystem: %s", out)
+			cmd := []string{"mkfs.ext4", "-F", "-L", string(part.label), dev}
+			if out, err := exec.Command(cmd[0], cmd[1:]...).CombinedOutput(); err != nil {
+				return &ErrExec{command: cmd, output: out}
 			}
 		}
 	}

=== modified file 'diskimage/errors.go'
--- diskimage/errors.go	2015-06-15 15:15:39 +0000
+++ diskimage/errors.go	2015-07-10 17:13:52 +0000
@@ -7,7 +7,10 @@
 //
 package diskimage
 
-import "fmt"
+import (
+	"fmt"
+	"strings"
+)
 
 // ErrMount represents a mount error
 type ErrMount struct {
@@ -30,3 +33,13 @@
 func (e ErrMapCount) Error() string {
 	return fmt.Sprintf("expected %d partitons but found %d", e.expectedParts, e.foundParts)
 }
+
+// ErrExec is an error from an external command
+type ErrExec struct {
+	output  []byte
+	command []string
+}
+
+func (e ErrExec) Error() string {
+	return fmt.Sprintf("error while executing external command %s: %s", strings.Join(e.command, " "), e.output)
+}