[MM-24753] Improves error message when plugin crashes during slash command (#15334)

Co-authored-by: Ali Farooq <ali.farooq0@pm.me>
Co-authored-by: Ben Schumacher <ben.schumacher@mattermost.com>

app/plugin_commands.go

@@ -4,6 +4,7 @@
 package app
 
 import (
+	"fmt"
 	"net/http"
 	"net/url"
 	"strings"
@@ -136,6 +137,11 @@ func (a *App) tryExecutePluginCommand(args *model.CommandArgs) (*model.Command,
 		return nil, nil, nil
 	}
 
+	// Checking if plugin is working or not
+	if err := pluginsEnvironment.PerformHealthCheck(matched.PluginId); err != nil {
+		return matched.Command, nil, model.NewAppError("ExecutePluginCommand", "model.plugin_command_error.error.app_error", map[string]interface{}{"Command": trigger}, "err= Plugin has recently crashed: "+matched.PluginId, http.StatusInternalServerError)
+	}
+
 	pluginHooks, err := pluginsEnvironment.HooksForPlugin(matched.PluginId)
 	if err != nil {
 		return matched.Command, nil, model.NewAppError("ExecutePluginCommand", "model.plugin_command.error.app_error", nil, "err="+err.Error(), http.StatusInternalServerError)
@@ -150,5 +156,11 @@ func (a *App) tryExecutePluginCommand(args *model.CommandArgs) (*model.Command,
 	}
 
 	response, appErr := pluginHooks.ExecuteCommand(a.PluginContext(), args)
+
+	// Checking if plugin crashed after running the command
+	if err := pluginsEnvironment.PerformHealthCheck(matched.PluginId); err != nil {
+		errMessage := fmt.Sprintf("err= Plugin %s crashed due to /%s command", matched.PluginId, trigger)
+		return matched.Command, nil, model.NewAppError("ExecutePluginCommand", "model.plugin_command_crash.error.app_error", map[string]interface{}{"Command": trigger, "PluginId": matched.PluginId}, errMessage, http.StatusInternalServerError)
+	}
 	return matched.Command, response, appErr
 }