Please consider adding back the woocommerce_product_default_attributes filter

[jnachtigall]

There used to be a woocommerce_product_default_attributes filter for the default variation attributes. I used this in 2.6 for programatically selecting a certain a certain product variation. (e.g. 3 different variants, but 2 of them are sold out, so we select the only one being not sold out).

This filter does not work anymore in WC 3 since it has been move to a deprecated method that is not called any more from core:

woocommerce/includes/legacy/abstract-wc-legacy-product.php

Lines 157 to 166 in 3522857

	/**
	* If set, get the default attributes for a variable product.
	*
	* @deprecated 3.0.0
	* @return array
	*/
	public function get_variation_default_attributes() {
	wc_deprecated_function( 'WC_Product_Variable::get_variation_default_attributes', '3.0', 'WC_Product::get_default_attributes' );
	return apply_filters( 'woocommerce_product_default_attributes', $this->get_default_attributes(), $this );
	}

I cannot find any upgrade, migration or changelog notes on how to do handle the removal of this filter.

At Stackoverflow a user suggests to use the woocommerce_before_add_to_cart_form action to get the default variation, mangle it and then set them back to the product. This seems overly complicated and a filter should be there for this.

Would you consider adding the old woocommerce_product_default_attributes or a filter with a new name back to either public function get_variation_default_attributes():

woocommerce/includes/class-wc-product-variable.php

Lines 235 to 240 in d5e98e8

	public function get_variation_default_attribute( $attribute_name ) {
	$defaults = $this->get_default_attributes();
	$attribute_name = sanitize_title( $attribute_name );
	return isset( $defaults[ $attribute_name ] ) ? $defaults[ $attribute_name ] : '';
	}

or get_default_attributes():

woocommerce/includes/abstracts/abstract-wc-product.php

Lines 526 to 535 in 28a4e88

	/**
	* Get default attributes.
	*
	* @since 3.0.0
	* @param string $context What the value is for. Valid values are view and edit.
	* @return array
	*/
	public function get_default_attributes( $context = 'view' ) {
	return $this->get_prop( 'default_attributes', $context );
	}

?

Otherwise I'll go down the action road but as said there should be a filter for this.

[lomars]

You can use the filter woocommerce_product_get_default_attributes which has 2 arguments $attributes and $product.

So no need to add back woocommerce_product_default_attributes filter hook.

[jnachtigall]

@lomars thanks so much, this works! The 2 arguments are even the same like for the old filter, so in fact it looks like it was more or less just renamed.

FWIW, I find it strange that this filter can neither be found on GitHub nor on the hooks API docs. That's and also with DDG is where I search for 1h or so without finding...

I'll change the subject, so maybe to docs could be made to include this filter, too.
Edit: No, I'll file a separate bug instead :)

[lomars]

This hook can not be referenced as it's a dynamic hook

Explanations:

Since Woocommerce 3 and new introduced CRUDS setter methods, when a method is using get_prop() WC_Data method, a dynamic hook based on the object type and the method name can be used (essentially for frontend: "view" context)…

See this line $value = apply_filters( $this->get_hook_prefix() . $prop, $value, $this ); in

woocommerce/includes/abstracts/abstract-wc-data.php

Lines 600 to 623 in b2e4052

	/**
	* Gets a prop for a getter method.
	*
	* Gets the value from either current pending changes, or the data itself.
	* Context controls what happens to the value before it's returned.
	*
	* @since 3.0.0
	* @param string $prop Name of prop to get.
	* @param string $context What the value is for. Valid values are view and edit.
	* @return mixed
	*/
	protected function get_prop( $prop, $context = 'view' ) {
	$value = null;
	if ( array_key_exists( $prop, $this->data ) ) {
	$value = array_key_exists( $prop, $this->changes ) ? $this->changes[ $prop ] : $this->data[ $prop ];
	if ( 'view' === $context ) {
	$value = apply_filters( $this->get_hook_prefix() . $prop, $value, $this );
	}
	}
	return $value;
	}

and this linereturn 'woocommerce_' . $this->object_type . '_get_'; in

woocommerce/includes/abstracts/abstract-wc-data.php

Lines 590 to 598 in b2e4052

	/**
	* Prefix for action and filter hooks on data.
	*
	* @since 3.0.0
	* @return string
	*/
	protected function get_hook_prefix() {
	return 'woocommerce_' . $this->object_type . '_get_';
	}

So the filter hook is dynamically made this way (where $this->object_type is equal to 'product'):
'woocommerce_' . $this->object_type . '_get_' . 'default_attributes'

with 2 arguments:

• $default_attributes (the property value that replace $value)
• $product (the class instance object that replace $this)…

Related update on StackOverFlow