When creating a module, I got the following error message:

The website encountered an unexpected error. Please try again later.

InvalidArgumentException: The form argument \Drupal\my_module\Form\MyForm is not a valid form. in Drupal\Core\Form\FormBuilder->getFormId() (line 190 of core/lib/Drupal/Core/Form/FormBuilder.php).

The issue was that my form filename was not correct (it should be named MyForm.php, but if it's called MyForm_Wrong.php or something like that, the system can't find it. The error message should therefore be:

The website encountered an unexpected error. Please try again later.

InvalidArgumentException: The form argument \Drupal\my_module\Form\MyForm is not a valid form. in Drupal\Core\Form\FormBuilder->getFormId() (line 190 of core/lib/Drupal/Core/Form/FormBuilder.php). Reason: Expected form file (MyForm.php) not found in folder: my_module/src/Form

This post solved my problem, and this person also suggested a better error message should have been given: https://drupal.stackexchange.com/questions/199828/call-a-custom-form-in-node-template

p.s. apologies if I assigned this to the incorrect component. I made a guess at user.modules.

As ever, huge thanks :)

Comments

CatsFromStonehenge created an issue. See original summary.

cilefen’s picture

cilefen CreditAttribution: cilefen commented
Title: Unclear error message for module » Throw a specific exception in FormBuilder if a form class cannot be loaded because the developer did not put the file in the correct path to be autoloaded
Version: 8.2.x-dev » 8.4.x-dev
Component: user.module » forms system
Issue tags: -modules, -error message +DX (Developer Experience)

Before adding tags read the issue tag guidelines. Feature requests go in 8.4.x at this phase. This is the forms system.

Version: 8.4.x-dev » 8.5.x-dev

Drupal 8.4.0-alpha1 will be released the week of July 31, 2017, which means new developments and disruptive changes should now be targeted against the 8.5.x-dev branch. For more information see the Drupal 8 minor version schedule and the Allowed changes during the Drupal 8 release cycle.

Version: 8.5.x-dev » 8.6.x-dev

Drupal 8.5.0-alpha1 will be released the week of January 17, 2018, which means new developments and disruptive changes should now be targeted against the 8.6.x-dev branch. For more information see the Drupal 8 minor version schedule and the Allowed changes during the Drupal 8 release cycle.

Version: 8.6.x-dev » 8.7.x-dev

Drupal 8.6.0-alpha1 will be released the week of July 16, 2018, which means new developments and disruptive changes should now be targeted against the 8.7.x-dev branch. For more information see the Drupal 8 minor version schedule and the Allowed changes during the Drupal 8 release cycle.

Version: 8.7.x-dev » 8.8.x-dev

Drupal 8.7.0-alpha1 will be released the week of March 11, 2019, which means new developments and disruptive changes should now be targeted against the 8.8.x-dev branch. For more information see the Drupal 8 minor version schedule and the Allowed changes during the Drupal 8 release cycle.

Version: 8.8.x-dev » 8.9.x-dev

Drupal 8.8.0-alpha1 will be released the week of October 14th, 2019, which means new developments and disruptive changes should now be targeted against the 8.9.x-dev branch. (Any changes to 8.9.x will also be committed to 9.0.x in preparation for Drupal 9’s release, but some changes like significant feature additions will be deferred to 9.1.x.). For more information see the Drupal 8 and 9 minor version schedule and the Allowed changes during the Drupal 8 and 9 release cycles.

Version: 8.9.x-dev » 9.1.x-dev

Drupal 8.9.0-beta1 was released on March 20, 2020. 8.9.x is the final, long-term support (LTS) minor release of Drupal 8, which means new developments and disruptive changes should now be targeted against the 9.1.x-dev branch. For more information see the Drupal 8 and 9 minor version schedule and the Allowed changes during the Drupal 8 and 9 release cycles.

Ramya Balasubramanian’s picture

Ramya Balasubramanian CreditAttribution: Ramya Balasubramanian at Srijan | A Material+ Company for Drupal India Association commented
Assigned: Unassigned » Ramya Balasubramanian
Ramya Balasubramanian’s picture

Ramya Balasubramanian CreditAttribution: Ramya Balasubramanian at Srijan | A Material+ Company for Drupal India Association commented
Assigned: Ramya Balasubramanian » Unassigned

I can't able to reproduce the issues. So I am unassigning this ticket.

Version: 9.1.x-dev » 9.2.x-dev

Drupal 9.1.0-alpha1 will be released the week of October 19, 2020, which means new developments and disruptive changes should now be targeted for the 9.2.x-dev branch. For more information see the Drupal 9 minor version schedule and the Allowed changes during the Drupal 9 release cycle.

Version: 9.2.x-dev » 9.3.x-dev

Drupal 9.2.0-alpha1 will be released the week of May 3, 2021, which means new developments and disruptive changes should now be targeted for the 9.3.x-dev branch. For more information see the Drupal core minor version schedule and the Allowed changes during the Drupal core release cycle.

Version: 9.3.x-dev » 9.4.x-dev

Drupal 9.3.0-rc1 was released on November 26, 2021, which means new developments and disruptive changes should now be targeted for the 9.4.x-dev branch. For more information see the Drupal core minor version schedule and the Allowed changes during the Drupal core release cycle.

Version: 9.4.x-dev » 9.5.x-dev

Drupal 9.4.0-alpha1 was released on May 6, 2022, which means new developments and disruptive changes should now be targeted for the 9.5.x-dev branch. For more information see the Drupal core minor version schedule and the Allowed changes during the Drupal core release cycle.

Version: 9.5.x-dev » 10.1.x-dev

Drupal 9.5.0-beta2 and Drupal 10.0.0-beta2 were released on September 29, 2022, which means new developments and disruptive changes should now be targeted for the 10.1.x-dev branch. For more information see the Drupal core minor version schedule and the Allowed changes during the Drupal core release cycle.

Version: 10.1.x-dev » 11.x-dev

Drupal core is moving towards using a “main” branch. As an interim step, a new 11.x branch has been opened, as Drupal.org infrastructure cannot currently fully support a branch named main. New developments and disruptive changes should now be targeted for the 11.x branch, which currently accepts only minor-version allowed changes. For more information, see the Drupal core minor version schedule and the Allowed changes during the Drupal core release cycle.