Validates creating a new user

- If a new user is created and neither the username, first name nor last name is set, a hint is displayed and the user is still in the creating mode.
- Also prevents that the client queries a user that does not exist.

client/src/app/shared/validators/one-of-validator.ts

@@ -0,0 +1,27 @@
+import { ValidationErrors, AbstractControl } from '@angular/forms';
+
+/**
+ * Custom validator class
+ * Several strings can be passed as `keys` of the form group.
+ * This validator ensures that at least one of the fields behind the given keys has a value.
+ */
+export class OneOfValidator {
+    /**
+     * Function to confirm that at least one of the given form controls has a valid value.
+     *
+     * @param keys Undefined amount of form control names.
+     *
+     * @returns An error if all of these form controls have no valid values or null if at least one is filled.
+     */
+    public static validation(...keys: string[]): (control: AbstractControl) => ValidationErrors | null {
+        return (control: AbstractControl): ValidationErrors | null => {
+            const formControls = keys.map(key => control.get(key));
+
+            const noOneSet = formControls.every(
+                formControl => (formControl && formControl.value === '') || !formControl
+            );
+
+            return noOneSet ? { noOneSet: true } : null;
+        };
+    }
+}

client/src/app/site/users/components/user-detail/user-detail.component.ts

@@ -15,6 +15,7 @@ import { UserRepositoryService } from 'app/core/repositories/users/user-reposito
 import { ViewUser } from '../../models/view-user';
 import { ViewGroup } from '../../models/view-group';
 import { GroupRepositoryService } from 'app/core/repositories/users/group-repository.service';
+import { OneOfValidator } from 'app/shared/validators/one-of-validator';
 
 /**
  * Users detail component for both new and existing users
@@ -226,7 +227,8 @@ export class UserDetailComponent extends BaseViewComponent implements OnInit {
      * initialize the form with default values
      */
     public createForm(): void {
-        this.personalInfoForm = this.formBuilder.group({
+        this.personalInfoForm = this.formBuilder.group(
+            {
                 username: [''],
                 title: [''],
                 first_name: [''],
@@ -243,7 +245,11 @@ export class UserDetailComponent extends BaseViewComponent implements OnInit {
                 comment: [''],
                 is_active: [true],
                 default_password: ['']
-        });
+            },
+            {
+                validators: OneOfValidator.validation('username', 'first_name', 'last_name')
+            }
+        );
 
         // patch the form only for existing users
         if (!this.newUser) {
@@ -342,11 +348,26 @@ export class UserDetailComponent extends BaseViewComponent implements OnInit {
      * Save / Submit a user
      */
     public async saveUser(): Promise<void> {
+        if (this.personalInfoForm.invalid) {
+            let hint = '';
+            if (this.personalInfoForm.errors) {
+                hint = 'At least one of username, first name or last name has to be set.';
+            } else {
+                for (const formControl in this.personalInfoForm.controls) {
+                    if (this.personalInfoForm.get(formControl).errors) {
+                        hint = formControl + ' is incorrect.';
+                    }
+                }
+            }
+            this.raiseError(this.translate.instant(hint));
+            return;
+        }
         try {
             if (this.newUser) {
+                await this.repo.create(this.personalInfoForm.value).then(() => {
                     this.newUser = false;
-                await this.repo.create(this.personalInfoForm.value);
                     this.router.navigate([`./users/`]);
+                }, this.raiseError);
             } else {
                 // TODO (Issue #3962): We need a waiting-State, so if autoupdates come before the response,
                 // the user is also updated.