From 37f5996a9965a663602772171589eb593044b7fa Mon Sep 17 00:00:00 2001
From: Subhash Chandra <tmayad+github@gmail.com>
Date: Sun, 19 Jan 2020 09:31:56 +0530
Subject: [PATCH 1/2] Added overwrite option to merge node

---
 packages/nodes-base/nodes/Merge.node.ts | 35 ++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/packages/nodes-base/nodes/Merge.node.ts b/packages/nodes-base/nodes/Merge.node.ts
index d63d5020a2..becf1ff17f 100644
--- a/packages/nodes-base/nodes/Merge.node.ts
+++ b/packages/nodes-base/nodes/Merge.node.ts
@@ -159,6 +159,34 @@ export class Merge implements INodeType {
 				default: 'input1',
 				description: 'Defines of which input the data should be used as output of node.',
 			},
+			{
+				displayName: 'Overwrite',
+				name: 'overwrite',
+				type: 'options',
+				displayOptions: {
+					show: {
+						mode: [
+							'mergeByKey',
+						],
+					},
+				},
+				options: [
+					{
+						name: 'Always',
+						value: 'always',
+					},
+					{
+						name: 'If Missing',
+						value: 'undefined',
+					},
+					{
+						name: 'If Blank',
+						value: 'blank'
+					},
+				],
+				default: 'always',
+				description: 'Select when to overwrite the values from Input1 with values from Input 2.',
+			}
 		]
 	};
 
@@ -263,6 +291,7 @@ export class Merge implements INodeType {
 
 			const propertyName1 = this.getNodeParameter('propertyName1', 0) as string;
 			const propertyName2 = this.getNodeParameter('propertyName2', 0) as string;
+			const overwrite = this.getNodeParameter('overwrite', 0) as string;
 
 			const dataInput2 = this.getInputData(1);
 			if (!dataInput2 || !propertyName1 || !propertyName2) {
@@ -354,7 +383,11 @@ export class Merge implements INodeType {
 
 						for (key of Object.keys(copyData[referenceValue as string].json)) {
 							// TODO: Currently only copies json data and no binary one
-							entry.json[key] = copyData[referenceValue as string].json[key];
+							let value = copyData[referenceValue as string].json[key];
+
+							if (overwrite === 'always' || (overwrite === 'undefined' && ['null', 'undefined'].includes(typeof value)) || (overwrite === 'blank' && !value)) {
+								entry.json[key] = value
+							}
 						}
 					} else {
 						// For "keepKeyMatches" we add it as it is

From c5d4c6a1d318f782b44d3fb0c6795d108b37d3dc Mon Sep 17 00:00:00 2001
From: Jan Oberhauser <jan.oberhauser@gmail.com>
Date: Sun, 19 Jan 2020 14:01:10 -0600
Subject: [PATCH 2/2] :zap: Fix overwrite option on Merge-Node

---
 packages/nodes-base/nodes/Merge.node.ts | 26 +++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/packages/nodes-base/nodes/Merge.node.ts b/packages/nodes-base/nodes/Merge.node.ts
index 644cee2101..59bf4cc185 100644
--- a/packages/nodes-base/nodes/Merge.node.ts
+++ b/packages/nodes-base/nodes/Merge.node.ts
@@ -179,14 +179,17 @@ export class Merge implements INodeType {
 					{
 						name: 'Always',
 						value: 'always',
+						description: 'Always overwrites everything.',
+					},
+					{
+						name: 'If Blank',
+						value: 'blank',
+						description: 'Overwrites only values of "null", "undefined" or empty string.',
 					},
 					{
 						name: 'If Missing',
 						value: 'undefined',
-					},
-					{
-						name: 'If Blank',
-						value: 'blank'
+						description: 'Only adds values which do not exist yet.',
 					},
 				],
 				default: 'always',
@@ -404,11 +407,18 @@ export class Merge implements INodeType {
 						entry = JSON.parse(JSON.stringify(entry));
 
 						for (key of Object.keys(copyData[referenceValue as string].json)) {
-							// TODO: Currently only copies json data and no binary one
-							let value = copyData[referenceValue as string].json[key];
+							if (key === propertyName2) {
+								continue;
+							}
 
-							if (overwrite === 'always' || (overwrite === 'undefined' && ['null', 'undefined'].includes(typeof value)) || (overwrite === 'blank' && !value)) {
-								entry.json[key] = value
+							// TODO: Currently only copies json data and no binary one
+							const value = copyData[referenceValue as string].json[key];
+							if (
+								overwrite === 'always' ||
+								(overwrite === 'undefined' && !entry.json.hasOwnProperty(key)) ||
+								(overwrite === 'blank' && [null, undefined, ''].includes(entry.json[key] as string))
+							) {
+								entry.json[key] = value;
 							}
 						}
 					} else {