Plugins: Tidy up CLI code (#67813)

* more tidying

* move some things around

* more tidying

* fix linter

pkg/plugins/plugins.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"io/fs"
 	"path"
 	"runtime"
@@ -24,6 +25,7 @@ var (
 	ErrFileNotExist              = errors.New("file does not exist")
 	ErrPluginFileRead            = errors.New("file could not be read")
 	ErrUninstallInvalidPluginDir = errors.New("cannot recognize as plugin folder")
+	ErrInvalidPluginJSON         = errors.New("did not find valid type or id properties in plugin.json")
 )
 
 type Plugin struct {
@@ -139,6 +141,44 @@ type JSONData struct {
 	Executable string `json:"executable,omitempty"`
 }
 
+func ReadPluginJSON(reader io.Reader) (JSONData, error) {
+	plugin := JSONData{}
+	if err := json.NewDecoder(reader).Decode(&plugin); err != nil {
+		return JSONData{}, err
+	}
+
+	if err := validatePluginJSON(plugin); err != nil {
+		return JSONData{}, err
+	}
+
+	if plugin.ID == "grafana-piechart-panel" {
+		plugin.Name = "Pie Chart (old)"
+	}
+
+	if len(plugin.Dependencies.Plugins) == 0 {
+		plugin.Dependencies.Plugins = []Dependency{}
+	}
+
+	if plugin.Dependencies.GrafanaVersion == "" {
+		plugin.Dependencies.GrafanaVersion = "*"
+	}
+
+	for _, include := range plugin.Includes {
+		if include.Role == "" {
+			include.Role = org.RoleViewer
+		}
+	}
+
+	return plugin, nil
+}
+
+func validatePluginJSON(data JSONData) error {
+	if data.ID == "" || !data.Type.IsValid() {
+		return ErrInvalidPluginJSON
+	}
+	return nil
+}
+
 func (d JSONData) DashboardIncludes() []*Includes {
 	result := []*Includes{}
 	for _, include := range d.Includes {