Merge PluginError into Result

Signed-off-by: Deep Debroy <ddebroy@apple.com>

client.go

@@ -108,20 +108,27 @@ func (c *Client) invokePlugin(ctx context.Context, name string, r *types.Request
 	cmd.Stderr = os.Stderr
 
 	out, err := cmd.Output()
+	msg := "output:"
+	if len(out) > 0 {
+		msg = fmt.Sprintf("%s %q", msg, out)
+	} else {
+		msg = fmt.Sprintf("%s <empty>", msg)
+	}
 	if err != nil {
-		// ExitError is returned when there is a non-zero exit status
-		if _, ok := err.(*exec.ExitError); ok {
-			var pe types.PluginError
-			if err := json.Unmarshal(out, &pe); err != nil {
-				return nil, errors.Wrapf(err, "%s: %s", name, out)
-			}
-			return nil, &pe
+		if exitErr, ok := err.(*exec.ExitError); ok {
+			// ExitError is returned when there is a non-zero exit status
+			msg = fmt.Sprintf("%s exit code: %d", msg, exitErr.ExitCode())
+		} else {
+			// plugin did not get a chance to run, return exec err
+			return nil, err
 		}
-		return nil, errors.Wrapf(err, "%s: %s", name, out)
 	}
 	var result types.Result
 	if err := json.Unmarshal(out, &result); err != nil {
-		return nil, err
+		return nil, errors.Errorf("failed to unmarshal plugin output: %s: %s", err.Error(), msg)
+	}
+	if result.Err() != nil {
+		return nil, result.Err()
 	}
 	return &result, nil
 }

skel/skel.go

@@ -31,15 +31,19 @@ func Run(ctx context.Context, plugin Plugin) error {
 	case "invoke":
 		result, err := plugin.Invoke(ctx, &request)
 		if err != nil {
-			pe := types.NewPluginError(plugin.Type(), err)
-			if err := enc.Encode(pe); err != nil {
-				return err
-			}
-			return pe
+			// if the plugin sets ErrorMessage we ignore it
+			result = request.NewResult(plugin.Type())
+			result.Error = err.Error()
+		}
+		if err := enc.Encode(result); err != nil {
+			return errors.Wrap(err, "unable to encode plugin error to stdout")
 		}
-		out = result
 	default:
-		return errors.New("undefined arg")
+		result := request.NewResult(plugin.Type())
+		result.Error = fmt.Sprintf("invalid arg %s", os.Args[1])
+		if err := enc.Encode(result); err != nil {
+			return errors.Wrap(err, "unable to encode invalid parameter error to stdout")
+		}
 	}
-	return enc.Encode(out)
+	return nil
 }

types/v1/types.go

@@ -2,7 +2,7 @@ package v1
 
 import (
 	"encoding/json"
-	"fmt"
+	"github.com/pkg/errors"
 )
 
 // Plugin type and configuration
@@ -81,27 +81,6 @@ type Request struct {
 	Results []*Result `json:"results,omitempty"`
 }
 
-// NewPluginError returns a plugin error
-func NewPluginError(name string, err error) error {
-	return &PluginError{
-		Plugin:  name,
-		Message: err.Error(),
-	}
-}
-
-// PluginError for specific plugin execution
-type PluginError struct {
-	// Plugin name
-	Plugin string `json:"plugin"`
-	// Message for the error
-	Message string `json:"message"`
-}
-
-// Error as a string
-func (p *PluginError) Error() string {
-	return fmt.Sprintf("%s: %s", p.Plugin, p.Message)
-}
-
 // IsSandbox returns true if the request is for a sandbox
 func (r *Request) IsSandbox() bool {
 	return r.ID == r.SandboxID
@@ -122,6 +101,16 @@ type Result struct {
 	Plugin string `json:"plugin"`
 	// Version of the plugin
 	Version string `json:"version"`
+	// Error message in case of failures
+	Error string `json:"error"`
 	// Metadata specific to actions taken by the plugin
 	Metadata map[string]string `json:"metadata,omitempty"`
 }
+
+// Err creates an Error object if ErrorMessage is populated
+func (r *Result) Err() error {
+	if r.Error != "" {
+		return errors.New(r.Error)
+	}
+	return nil
+}