Optional zeebe:input and zeebe:output

src/provider/cloud-element-templates/CreateHelper.js

@@ -74,3 +74,20 @@ export function createTaskDefinitionWithType(value, bpmnFactory) {
     type: value
   });
 }
+
+/**
+ * Retrieves whether an element should be updated for a given property.
+ *
+ * That matches once
+ * a) the property value is not empty, or
+ * b) the property is not optional
+ *
+ * @param {String} value
+ * @param {Object} property
+ * @returns {Boolean}
+ */
+export function shouldUpdate(value, property) {
+  const { optional } = property;
+
+  return value || !optional;
+}

src/provider/cloud-element-templates/cmd/ChangeElementTemplateHandler.js

@@ -11,7 +11,8 @@ import {
   createInputParameter,
   createOutputParameter,
   createTaskDefinitionWithType,
-  createTaskHeader
+  createTaskHeader,
+  shouldUpdate
 } from '../CreateHelper';
 
 import {
@@ -279,7 +280,23 @@ export default class ChangeElementTemplateHandler {
       // (2) update old inputs and outputs
       if (oldProperty && oldInputOrOutput) {
 
+        // (2a) exclude old inputs and outputs from cleanup, unless
+        // a) optional and has empty value, and
+        // b) not changed
+        if (
+          shouldUpdate(newPropertyValue, newProperty) ||
+          propertyChanged(oldInputOrOutput, oldProperty)
+        ) {
+          if (is(oldInputOrOutput, 'zeebe:Input')) {
+            remove(oldInputs, oldInputOrOutput);
+          } else {
+            remove(oldOutputs, oldInputOrOutput);
+          }
+        }
+
+        // (2a) do updates (unless changed)
         if (!propertyChanged(oldInputOrOutput, oldProperty)) {
+
           if (is(oldInputOrOutput, 'zeebe:Input')) {
             properties = {
               source: newPropertyValue
@@ -296,16 +313,10 @@ export default class ChangeElementTemplateHandler {
             properties
           });
         }
-
-        if (is(oldInputOrOutput, 'zeebe:Input')) {
-          remove(oldInputs, oldInputOrOutput);
-        } else {
-          remove(oldOutputs, oldInputOrOutput);
-        }
       }
 
-      // (3) add new inputs and outputs
-      else {
+      // (3) add new inputs and outputs (unless optional)
+      else if (shouldUpdate(newPropertyValue, newProperty)) {
         if (newBindingType === 'zeebe:input') {
           propertyName = 'inputParameters';
 

src/provider/cloud-element-templates/properties/CustomProperties.js

@@ -31,7 +31,8 @@ import {
   createInputParameter,
   createOutputParameter,
   createTaskDefinitionWithType,
-  createTaskHeader
+  createTaskHeader,
+  shouldUpdate
 } from '../CreateHelper';
 
 import { createElement } from '../../../utils/ElementUtil';
@@ -337,6 +338,7 @@ function propertyGetter(element, property) {
 
     const {
       binding,
+      optional,
       value: defaultValue = ''
     } = property;
 
@@ -384,7 +386,8 @@ function propertyGetter(element, property) {
           return inputParameter.get('source');
         }
 
-        return defaultValue;
+        // allow empty values for optional parameters
+        return optional ? '' : defaultValue;
       }
 
       // zeebe:Output
@@ -395,7 +398,8 @@ function propertyGetter(element, property) {
           return outputParameter.get('target');
         }
 
-        return defaultValue;
+        // allow empty values for optional parameters
+        return optional ? '' : defaultValue;
       }
     }
 
@@ -425,7 +429,9 @@ function propertySetter(bpmnFactory, commandStack, element, property) {
   return function setValue(value) {
     let businessObject = getBusinessObject(element);
 
-    const { binding } = property;
+    const {
+      binding
+    } = property;
 
     const {
       name,
@@ -539,35 +545,41 @@ function propertySetter(bpmnFactory, commandStack, element, property) {
       // zeebe:Input
       if (type === ZEBBE_INPUT_TYPE) {
         const oldZeebeInputParameter = findInputParameter(ioMapping, binding);
-
-        const newZeebeInputParameter = createInputParameter(binding, value, bpmnFactory);
-
         const values = ioMapping.get('inputParameters').filter((value) => value !== oldZeebeInputParameter);
 
+        // do not persist empty parameters when configured as <optional>
+        if (shouldUpdate(value, property)) {
+          const newZeebeInputParameter = createInputParameter(binding, value, bpmnFactory);
+          values.push(newZeebeInputParameter);
+        }
+
         commands.push({
           cmd: 'element.updateModdleProperties',
           context: {
             element,
             moddleElement: ioMapping,
-            properties: { inputParameters: [ ...values, newZeebeInputParameter ] }
+            properties: { inputParameters: [ ...values ] }
           }
         });
       }
 
       // zeebe:Output
       if (type === ZEEBE_OUTPUT_TYPE) {
         const oldZeebeOutputParameter = findOutputParameter(ioMapping, binding);
-
-        const newZeebeOutputParameter = createOutputParameter(binding, value, bpmnFactory);
-
         const values = ioMapping.get('outputParameters').filter((value) => value !== oldZeebeOutputParameter);
 
+        // do not persist empty parameters when configured as <optional>
+        if (shouldUpdate(value, property)) {
+          const newZeebeOutputParameter = createOutputParameter(binding, value, bpmnFactory);
+          values.push(newZeebeOutputParameter);
+        }
+
         commands.push({
           cmd: 'element.updateModdleProperties',
           context: {
             element,
             moddleElement: ioMapping,
-            properties: { 'outputParameters': [ ...values, newZeebeOutputParameter ] }
+            properties: { 'outputParameters': [ ...values ] }
           }
         });
       }