Improve error message when function or trigger not import in engine (#…

…218)

Improve the error message when function or trigger not installed in engine

app/instances.go

@@ -87,7 +87,7 @@ func (a *App) createTriggers(tConfigs []*trigger.Config, runner action.Runner) (
 			var ok bool
 			ref, ok = support.GetAliasRef("trigger", tConfig.Ref)
 			if !ok {
-				return nil, fmt.Errorf("trigger [%s]'s 'ref' [%s] not imported", tConfig.Id, tConfig.Ref)
+				return nil, fmt.Errorf("unable to start trigger [%s], ref alias '%s' has no corresponding installed trigger", tConfig.Id, tConfig.Ref)
 			}
 		}
 

data/expression/script/gocc/ast/function.go

@@ -20,7 +20,7 @@ func NewFuncExpr(name interface{}, args interface{}) (Expr, error) {
 
 	f := function.Get(funcName)
 	if f == nil {
-		return nil, fmt.Errorf("function '%s' not registered", funcName)
+		return nil, fmt.Errorf("unable to parse expression, function [%s] is not installed", funcName)
 	}
 	fe := &funcExpr{f: f}