Fix retry logic since exec.Cmd cannot be reused

Author: Jonas Falck

cmd_apply.go

@@ -26,14 +26,14 @@ func (cmd CmdApply) Usage() string {
 }
 
 func ApplyRule(outputs Outputs, rule Rule) error {
-	var cmds []*exec.Cmd
+	var cmds commands
 	var err error
 
 	switch {
 	case rule.ConfigureSingle != "" || len(rule.ConfigureRow) > 0 || len(rule.ConfigureColumn) > 0:
 		cmds, err = BuildCommandOutputRow(rule, outputs)
 	case rule.ConfigureCommand != "":
-		cmds = []*exec.Cmd{exec.Command("sh", "-c", rule.ConfigureCommand)}
+		cmds = commands{command{"sh", "-c", rule.ConfigureCommand}}
 	default:
 		return fmt.Errorf("no output configuration for rule %v", rule.Name)
 	}
@@ -45,7 +45,7 @@ func ApplyRule(outputs Outputs, rule Rule) error {
 	foundError := false
 	for _, cmd := range cmds {
 		for i := 0; i < 4; i++ {
-			err = RunCommand(cmd)
+			err = RunCommand(cmd.Cmd())
 			if err == nil {
 				break
 			}

randr.go

@@ -496,11 +496,25 @@ func DetectOutputs() (Outputs, error) {
 	return RandrParse(bytes.NewReader(output))
 }
 
+type (
+	commands []command
+	command  []string
+)
+
+func (c command) Cmd() *exec.Cmd {
+	return exec.Command(c[0], c[1:]...) // #nosec
+}
+
+func newCommand(cmd string, args ...string) command {
+	c := command{cmd}
+	return append(c, args...)
+}
+
 // BuildCommandOutputRow return a sequence of calls to `xrandr` to configure
 // all named outputs in a row, left to right, given the currently active
 // Outputs and a list of output names, optionally followed by "@" and the
 // desired mode, e.g. LVDS1@1377x768.
-func BuildCommandOutputRow(rule Rule, current Outputs) ([]*exec.Cmd, error) {
+func BuildCommandOutputRow(rule Rule, current Outputs) (commands, error) {
 	var outputs []string
 	var row bool
 
@@ -606,18 +620,17 @@ func BuildCommandOutputRow(rule Rule, current Outputs) ([]*exec.Cmd, error) {
 		for _, enableArgs := range enableOutputArgs {
 			args = append(args, enableArgs...)
 		}
-		cmd := exec.Command(command, args...)
-		return []*exec.Cmd{cmd}, nil
+		return commands{newCommand(command, args...)}, nil
 	}
 
 	V("splitting the configuration into several calls to xrandr\n")
 
 	// otherwise return several calls to xrandr
-	cmds := []*exec.Cmd{}
+	cmds := commands{}
 
 	// disable an output
 	if len(disableOutputArgs) > 0 {
-		cmds = append(cmds, exec.Command(command, disableOutputArgs[0]...))
+		cmds = append(cmds, newCommand(command, disableOutputArgs[0]...))
 		disableOutputArgs = disableOutputArgs[1:]
 	}
 
@@ -633,7 +646,7 @@ func BuildCommandOutputRow(rule Rule, current Outputs) ([]*exec.Cmd, error) {
 			enableOutputArgs = enableOutputArgs[1:]
 		}
 
-		cmds = append(cmds, exec.Command(command, args...))
+		cmds = append(cmds, newCommand(command, args...))
 	}
 
 	return cmds, nil

rule.go

@@ -26,14 +26,20 @@ type Rule struct {
 }
 
 func (r Rule) OutputsDiff(old Rule) Outputs {
-	outputs := []string{r.ConfigureSingle}
+	outputs := []string{}
+	if r.ConfigureSingle != "" {
+		outputs = append(outputs, r.ConfigureSingle)
+	}
 	outputs = append(outputs, r.ConfigureRow...)
 	outputs = append(outputs, r.ConfigureColumn...)
 	for k, v := range outputs {
 		outputs[k] = strings.SplitN(v, "@", 2)[0]
 	}
 
-	outputsOld := []string{old.ConfigureSingle}
+	outputsOld := []string{}
+	if old.ConfigureSingle != "" {
+		outputsOld = append(outputsOld, old.ConfigureSingle)
+	}
 	outputsOld = append(outputsOld, old.ConfigureRow...)
 	outputsOld = append(outputsOld, old.ConfigureColumn...)
 	for k, v := range outputsOld {