From 9da0c1c8844103a661139f652b6337ff15d3f280 Mon Sep 17 00:00:00 2001
From: Jan Oberhauser <jan.oberhauser@gmail.com>
Date: Fri, 3 Apr 2020 19:37:28 +0200
Subject: [PATCH] :zap: Display errors in expressions

---
 packages/editor-ui/src/components/ExpressionInput.vue |  6 +++---
 packages/workflow/src/Workflow.ts                     | 10 +++-------
 2 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/packages/editor-ui/src/components/ExpressionInput.vue b/packages/editor-ui/src/components/ExpressionInput.vue
index 7ee68be5af..543eb12f22 100644
--- a/packages/editor-ui/src/components/ExpressionInput.vue
+++ b/packages/editor-ui/src/components/ExpressionInput.vue
@@ -166,11 +166,11 @@ export default mixins(
 				let returnValue;
 				try {
 					returnValue = this.resolveExpression(`=${variableName}`);
-				} catch (e) {
-					return 'invalid';
+				} catch (error) {
+					return `[invalid (${error.message})]`;
 				}
 				if (returnValue === undefined) {
-					return 'not found';
+					return '[not found]';
 				}
 
 				return returnValue;
diff --git a/packages/workflow/src/Workflow.ts b/packages/workflow/src/Workflow.ts
index a63060913c..816c009a1f 100644
--- a/packages/workflow/src/Workflow.ts
+++ b/packages/workflow/src/Workflow.ts
@@ -156,7 +156,8 @@ export class Workflow {
 	 * @memberof Workflow
 	 */
 	convertObjectValueToString(value: object): string {
-		return `[Object: ${JSON.stringify(value)}]`;
+		const typeName = Array.isArray(value) ? 'Array' : 'Object';
+		return `[${typeName}: ${JSON.stringify(value)}]`;
 	}
 
 
@@ -906,18 +907,13 @@ export class Workflow {
 		try {
 			const returnValue = tmpl.tmpl(parameterValue, data);
 			if (returnValue !== null && typeof returnValue === 'object') {
-				if (Object.keys(returnValue).length === 0) {
-					// When expression is incomplete it returns a Proxy which causes problems.
-					// Catch it with this code and return a proper error.
-					throw new Error('Expression is not valid.');
-				}
 				if (returnObjectAsString === true)  {
 					return this.convertObjectValueToString(returnValue);
 				}
 			}
 			return returnValue;
 		} catch (e) {
-			throw new Error('Expression is not valid.');
+			throw new Error(`Expression is not valid: ${e.message}`);
 		}
 	}