fix: plugin error message

cmd/notation/plugin/list.go

@@ -16,7 +16,10 @@
 import (
 	"errors"
 	"fmt"
+	"io/fs"
 	"os"
+	"runtime"
+	"syscall"
 	"text/tabwriter"
 
 	"github.com/notaryproject/notation-go/dir"
@@ -68,7 +71,27 @@
 			}
 		}
 		fmt.Fprintf(tw, "%s\t%s\t%s\t%v\t%v\t\n",
-			n, metaData.Description, metaData.Version, metaData.Capabilities, err)
+			n, metaData.Description, metaData.Version, metaData.Capabilities, userFriendlyError(err))
 	}
 	return tw.Flush()
 }
+
+// userFriendlyError optimizes the error message for the user.
+func userFriendlyError(err error) error {
+	if err == nil {
+		return nil
+	}
+	var pathError *fs.PathError
+	if errors.As(err, &pathError) {
+		// for plugin does not exist
+		if errors.Is(pathError, fs.ErrNotExist) {
+			return fmt.Errorf("%w. Each plugin executable must be located under $PLUGIN_DIRECTORY/{plugin-name} directory, with executable named as notation-{plugin-name}", pathError)
+		}
+
+		// for plugin is not executable
+		if pathError.Op == "fork/exec" && pathError.Err == syscall.Errno(8) {
+			return fmt.Errorf("%w. Please ensure that the plugin executable file is compatible with %s/%s", pathError, runtime.GOOS, runtime.GOARCH)
+		}
+	}
+	return err
+}

test/e2e/suite/plugin/list.go

@@ -14,6 +14,9 @@
 package plugin
 
 import (
+	"os"
+	"runtime"
+
 	. "github.com/notaryproject/notation/test/e2e/internal/notation"
 	"github.com/notaryproject/notation/test/e2e/internal/utils"
 	. "github.com/onsi/ginkgo/v2"
@@ -37,4 +40,41 @@ var _ = Describe("notation plugin list", func() {
 				MatchKeyWords("ERROR", "<nil>")
 		})
 	})
+
+	It("missing plugin binary", func() {
+		Host(nil, func(notation *utils.ExecOpts, _ *Artifact, vhost *utils.VirtualHost) {
+			// create azure-kv plugin directory
+			pluginDir := vhost.AbsolutePath(NotationDirName, "plugins", "azure-kv")
+			if err := os.MkdirAll(pluginDir, os.ModePerm); err != nil {
+				Fail(err.Error())
+			}
+
+			notation.Exec("plugin", "list").
+				MatchKeyWords("azure-kv").
+				MatchKeyWords("no such file or directory")
+		})
+	})
+
+	It("with invalid binary file", func() {
+		Host(nil, func(notation *utils.ExecOpts, _ *Artifact, vhost *utils.VirtualHost) {
+			// create azure-kv plugin directory
+			pluginDir := vhost.AbsolutePath(NotationDirName, "plugins", "azure-kv")
+			if err := os.MkdirAll(pluginDir, os.ModePerm); err != nil {
+				Fail(err.Error())
+			}
+
+			// create invalid plugin binary
+			invalidPluginBinary := vhost.AbsolutePath(NotationDirName, "plugins", "azure-kv", "notation-azure-kv")
+			if runtime.GOOS == "windows" {
+				invalidPluginBinary += ".exe"
+			}
+			if err := os.WriteFile(invalidPluginBinary, []byte("invalid"), 0755); err != nil {
+				Fail(err.Error())
+			}
+
+			notation.Exec("plugin", "list").
+				MatchKeyWords("azure-kv").
+				MatchKeyWords("exec format error")
+		})
+	})
 })