Global Default Configuration Is Always Overridden

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Global Default Configuration is Always Overridden: Understanding the Issue and Potential Solutions

Introduction

When working with the django-tomselect library, it's essential to understand how the default configuration is handled, especially when it comes to overriding settings in specific form fields. In this article, we'll delve into the expected behavior, actual behavior, and potential solutions to the issue of global default configuration being overridden.

Expected Behavior

When a default configuration is defined in settings.py, as shown below:

TOMSELECT = {
    ...
    "DEFAULT_CONFIG": {
        ...
        "use_htmx": True,
    }
}

And we create a form field with custom configurations:

gender = TomSelectChoiceField(
    config=TomSelectConfig(
        url="autocomplete:gender",
        placeholder="Select a Gender",
    )
)

We expect any default configuration from the settings that are not explicitly overridden in the form field to be included in the field's final configuration. In the example above, this means that the gender field should retain use_htmx=True as part of its configuration when the field is being built.

Actual Behavior

However, the actual behavior is different from the expected behavior. The use_htmx setting remains False when built. This is likely caused by the initialisation of the TomSelectConfig class, which initialises all fields with default values. As a result, when the following lines within the Mixins execute, it merges the global configuration with the specified configuration, and everything with a default value gets overridden by the “fresh” TomSelectConfig instance:

# Merge with GLOBAL_DEFAULT_CONFIG
base_config = GLOBAL_DEFAULT_CONFIG
if config and not isinstance(config, TomSelectConfig):
    config = TomSelectConfig(**config)
final_config = merge_configs(base_config, config)
self.config = final_config

Note that this behavior works fine for fields set to None, but not for boolean values or data that has already been initialized.

Potential Solution

When a dict is passed to the config=, existing configuration is updated based on the values unpacked from the dictionary:

gender = TomSelectChoiceField(
    config={
        "url": "autocomplete:gender",
        "placeholder": "Select a Gender",
    }
)

This approach ensures that the default configuration is not overridden, and the field's final configuration includes the specified settings.

Specifications

To reproduce the issue, ensure that you're using the following specifications:

  • Version: Django 5.0.12
  • Python: 3.12.9
  • django-tomselect: 2025.2.3
  • Platform: macOS

Conclusion

In conclusion, the global default configuration is always overridden when creating form fields with custom configurations. However, by passing a dict to the config= parameter, we can update the existing configuration and avoid overriding the default settings. This approach ensures that the field's final configuration includes the specified settings, while retaining the default configuration that's not explicitly overridden.

Troubleshooting Tips

If you're experiencing issues with the global default configuration being overridden, try the following troubleshooting tips:

  1. Check the settings.py file to ensure that the default configuration is defined correctly.
  2. Verify that the form field is created with the correct configuration, including any custom settings.
  3. Use the dict approach to update the existing configuration, as shown in the potential solution section.
  4. Review the django-tomselect documentation to ensure that you're using the library correctly.

By following these troubleshooting tips and understanding the potential solution, you should be able to resolve the issue of global default configuration being overridden and create form fields with custom configurations that include the specified settings.
Global Default Configuration is Always Overridden: Q&A

Q: What is the expected behavior when creating a form field with custom configurations?

A: When creating a form field with custom configurations, we expect any default configuration from the settings that are not explicitly overridden in the form field to be included in the field's final configuration.

Q: What is the actual behavior when creating a form field with custom configurations?

A: The actual behavior is that the default configuration from the settings is overridden by the custom configuration, even if the custom configuration does not explicitly override the default setting.

Q: Why is the default configuration being overridden?

A: The default configuration is being overridden because of the way the TomSelectConfig class is initialized. When a custom configuration is passed to the form field, it creates a new instance of TomSelectConfig with default values, which then overrides the default configuration from the settings.

Q: How can I prevent the default configuration from being overridden?

A: To prevent the default configuration from being overridden, you can pass a dict to the config= parameter, which will update the existing configuration instead of creating a new instance of TomSelectConfig.

Q: What is the difference between passing a dict and passing a TomSelectConfig instance to the config= parameter?

A: When passing a TomSelectConfig instance, it creates a new instance with default values, which then overrides the default configuration from the settings. When passing a dict, it updates the existing configuration without creating a new instance.

Q: Can I use both the default configuration and custom configuration in the same form field?

A: Yes, you can use both the default configuration and custom configuration in the same form field. By passing a dict to the config= parameter, you can update the existing configuration with the custom settings, while still retaining the default configuration.

Q: How do I know if the default configuration is being overridden?

A: You can check the form field's configuration by printing it out or using a debugger. If the default configuration is being overridden, you will see that the default setting is not present in the final configuration.

Q: Can I use this approach with other form fields or widgets?

A: Yes, this approach can be used with other form fields or widgets that use the config= parameter. However, you should check the documentation for each widget to ensure that it supports passing a dict to the config= parameter.

Q: Are there any other ways to prevent the default configuration from being overridden?

A: Yes, you can also use the merge_configs function to merge the default configuration with the custom configuration, instead of creating a new instance of TomSelectConfig. However, this approach may require more complex code and may not be as straightforward as passing a dict to the config= parameter.