fix(core): Make node execution order configurable, and backward-compatible (#6507)

* fix(core): Make node execution order configurable, and backward-compatible

* ⚡ Also add new Merge-Node behaviour

* ⚡ Fix typo

* Fix lint issue

* update labels

* rename legacy to v0

* remove the unnecessary log

* default all new workflows to use v1 execution-order

* remove the controller changes

* clone default settings to avoid it getting modified

---------

Co-authored-by: Jan Oberhauser <jan.oberhauser@gmail.com>

packages/editor-ui/src/components/WorkflowSettings.vue

@@ -13,6 +13,31 @@
 	>
 		<template #content>
 			<div v-loading="isLoading" class="workflow-settings" data-test-id="workflow-settings-dialog">
+				<el-row>
+					<el-col :span="10" class="setting-name">
+						{{ $locale.baseText('workflowSettings.executionOrder') + ':' }}
+					</el-col>
+					<el-col :span="14" class="ignore-key-press">
+						<n8n-select
+							v-model="workflowSettings.executionOrder"
+							placeholder="Select Execution Order"
+							size="medium"
+							filterable
+							:disabled="readOnlyEnv"
+							:limit-popper-width="true"
+							data-test-id="workflow-settings-execution-order"
+						>
+							<n8n-option
+								v-for="option in executionOrderOptions"
+								:key="option.key"
+								:label="option.value"
+								:value="option.key"
+							>
+							</n8n-option>
+						</n8n-select>
+					</el-col>
+				</el-row>
+
 				<el-row>
 					<el-col :span="10" class="setting-name">
 						{{ $locale.baseText('workflowSettings.errorWorkflow') + ':' }}
@@ -421,9 +446,14 @@ export default defineComponent({
 			saveDataSuccessExecutionOptions: [] as Array<{ key: string; value: string }>,
 			saveExecutionProgressOptions: [] as Array<{ key: string | boolean; value: string }>,
 			saveManualOptions: [] as Array<{ key: string | boolean; value: string }>,
+			executionOrderOptions: [
+				{ key: 'v0', value: 'v0 (legacy)' },
+				{ key: 'v1', value: 'v1 (recommended)' },
+			] as Array<{ key: string; value: string }>,
 			timezones: [] as Array<{ key: string; value: string }>,
 			workflowSettings: {} as IWorkflowSettings,
 			workflows: [] as IWorkflowShortResponse[],
+			executionOrder: 'v0',
 			executionTimeout: 0,
 			maxExecutionTimeout: 0,
 			timeoutHMS: { hours: 0, minutes: 0, seconds: 0 } as ITimeoutHMS,
@@ -535,6 +565,9 @@ export default defineComponent({
 		if (workflowSettings.maxExecutionTimeout === undefined) {
 			workflowSettings.maxExecutionTimeout = this.rootStore.maxExecutionTimeout;
 		}
+		if (workflowSettings.executionOrder === undefined) {
+			workflowSettings.executionOrder = 'v0';
+		}
 
 		this.workflowSettings = workflowSettings;
 		this.timeoutHMS = this.convertToHMS(workflowSettings.executionTimeout);