Disallow empty inputs on required input parameters in simplified workflow form

This is another attempt at
https://github.com/galaxyproject/galaxy/issues/13220, but taking into
account
https://github.com/galaxyproject/galaxy/issues/13220#issuecomment-1068054414
by limiting this to the simplified workflow form, where we can assume
input parameter optionality to have the correct meaning.

This makes it harder to submit a mandatory text parameter that can be
empty, but that is (at this point at least) a very fringe requirement.

If really needed you can make the parameter optional (and use pick_value
to fill in an empty string if null is not OK as a value).

client/src/components/Form/FormDisplay.vue

@@ -79,6 +79,10 @@ export default {
             type: Boolean,
             default: false,
         },
+        allowEmptyValueOnRequiredInput: {
+            type: Boolean,
+            default: false,
+        },
     },
     data() {
         return {
@@ -89,7 +93,7 @@ export default {
     },
     computed: {
         validation() {
-            return validateInputs(this.formIndex, this.formData);
+            return validateInputs(this.formIndex, this.formData, this.allowEmptyValueOnRequiredInput);
         },
     },
     watch: {

client/src/components/Form/utilities.js

@@ -104,7 +104,7 @@ export function matchInputs(index, response) {
  * @param{dict}   index     - Index of input elements
  * @param{dict}   values    - Dictionary of parameter values
  */
-export function validateInputs(index, values) {
+export function validateInputs(index, values, allowEmptyValueOnRequiredInput = false) {
     let batchN = -1;
     let batchSrc = null;
     for (const inputId in values) {
@@ -113,8 +113,10 @@ export function validateInputs(index, values) {
         if (!inputDef || inputDef.step_linked) {
             continue;
         }
-        if (inputValue == null && !inputDef.optional && inputDef.type != "hidden") {
-            return [inputId, "Please provide a value for this option."];
+        if (!inputDef.optional && inputDef.type != "hidden") {
+            if (inputValue == null || (allowEmptyValueOnRequiredInput && inputValue === "")) {
+                return [inputId, "Please provide a value for this option."];
+            }
         }
         if (inputDef.wp_linked && inputDef.text_value == inputValue) {
             return [inputId, "Please provide a value for this workflow parameter."];

client/src/components/Workflow/Run/WorkflowRunFormSimple.vue

@@ -43,7 +43,11 @@
                 </b-dropdown-form>
             </b-dropdown>
         </div>
-        <FormDisplay :inputs="formInputs" @onChange="onChange" @onValidation="onValidation" />
+        <FormDisplay
+            :inputs="formInputs"
+            :allowEmptyValueOnRequiredInput="true"
+            @onChange="onChange"
+            @onValidation="onValidation" />
         <!-- Options to default one way or the other, disable if admins want, etc.. -->
         <a href="#" class="workflow-expand-form-link" @click="$emit('showAdvanced')">Expand to full workflow form.</a>
     </div>
@@ -137,6 +141,8 @@ export default {
         onValidation(validation) {
             if (validation) {
                 Vue.set(this.stepValidations, validation[0], validation[1]);
+            } else {
+                this.stepValidations = {};
             }
         },
         reuseAllowed(user) {