Wrong "As low as" price display for configurable products when FPT is enabled

[twosg]

Preconditions and environment

• Magento 2.4.8-beta2 and newer
• 829e6a3

Steps to reproduce

1. At tax configuration, set "Catalog Prices" to "Excl. tax"
2. Set "Display Product Prices In Catalog" to "Incl. tax"
3. Enable FPT
4. Add a tax rule to calculate any amount of tax for the default tax destination country, for the default customer tax and the default product tax class
5. Go to any category page with configurable products within or to a product page of a configurable product

The "default" price (when no child product is selected yet) is shown with doubled taxes

Example:
Product Price: 100.00
19% tax applied = 119.00

But the price is displayed as 141.61 (It takes the 119.00 and adds 19% on top)

Expected result

"As low as" Price is shown correctly:

Actual result

Additional information

Cause is 829e6a3:

Specifically the Plugin for FinalPriceResolver. If it is disabled, the bug does not occur:

<type name="Magento\ConfigurableProduct\Pricing\Price\FinalPriceResolver">
        <plugin name="configurableProductPriceAdjustment" type="Magento\Weee\Plugin\ConfigurableProduct\Pricing\FinalPriceResolver" disabled="true"/>
    </type>

Of course it may be an issue more deeply in the calculation process, but as far as I understand it, the plugin is taking up the wrong price for its calculation or does not consider the Catalog Prices setting properly.

Release note

No response

Triage and priority

• Severity: S0 - Affects critical data or functionality and leaves users without workaround.
• Severity: S1 - Affects critical data or functionality and forces users to employ a workaround.
• Severity: S2 - Affects non-critical data or functionality and forces users to employ a workaround.
• Severity: S3 - Affects non-critical data or functionality and does not force users to employ a workaround.
• Severity: S4 - Affects aesthetics, professional look and feel, “quality” or “usability”.

[m2-assistant]

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[m2-assistant]

Hi @engcom-November. Thank you for working on this issue.
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[engcom-November]

Hello @twosg ,

Thank you for your report and collaboration.

Could you please confirm whether this issue is being caused by the use of Fixed Product Tax (FPT)?

In the meantime, we are marking this ticket as "Issue: Needs Update" pending your confirmation.

Thank you!

[Mendsft]

Hi @engcom-November ,I can confirm that the issue is related to the fixed product tax (FPT).
When this option is enabled, the issue can be reproduced, even if the configurable product does not have any FPT attributes.
Once disabled, everything works correctly.

[twosg]

Hello @engcom-November,
Yes it is caused by simply having FPT enabled, as @Mendsft explained.

[engcom-November]

Hello @twosg ,

Thank you for your report and collaboration.

We attempted to reproduce the issue in the latest 2.4-develop instances by following the provided steps and preconditions. We are able to reproduce the issue.

Steps to Reproduce:

• At tax configuration, set "Catalog Prices" to "Excl. tax"
• Set "Display Product Prices In Catalog" to "Incl. tax"
• Enable FPT
• Add a tax rule to calculate any amount of tax for the default tax destination country, for the default customer tax and the default product tax class
• Go to any category page with configurable products within or to a product page of a configurable product

We followed the preconditions and steps as provided and encountered the issue. Therefore, we are marking this ticket as "Issue: Confirmed."

Thank you!