Currency rate applying twice for configurable products

[sergeynezbritskiy]

Description

When I set up multiple currencies and go to product page, then switching from default currency will cause applying currency rate twice (for configurable products only)

Preconditions

• Create configurable product with two configurations with prices NOK 10 000 and NOK 5 000 respectively.

Steps to reproduce

• Go to frontend product page, I see price 5 000 NOK, but when switch currency to EUR, i see price 50 EUR.
• Setup multiple curencies: NOK (default, base currency), EUR.
• Configured currency rate 1 NOK = 0.1000 EUR
• Go to created product page on frontend
• Change store currency from NOK to EUR

Expected result

Price should be displayed 500.00 EUR

Actual result

Product price displayed 50.00 EUR

Additional information

I even can see some price blinking when page is loading from 500.00 to 50.00, you can see it on the video below https://www.screencast.com/t/IqRI8tMkYJi
So price for configurations is calculating correctly, and seems like it is calculating twice for configurable product price.
The same issues with other currencies.
Tested on Magento versions: 2.1.6 and 2.1.7 (2.1.6 - fresh vesion of Magento with default theme Luma)
OS: Ubuntu Ubuntu 14.04.5 LTS and Windows 10 x64
PHP 5.6.30
Apache 2.4

[veloraven]

@sergeynezbritskiy thank you for your feedback.
Please, format this issue according to the Issue reporting guidelines: with steps to reproduce, actual result and expected result.

[sergeynezbritskiy]

@veloraven done

[VasylShvorak]

@sergeynezbritskiy Thanks for reporting this issue. Created internal issue MAGETWO-71029 to investigate and track this issue.

[Danielc3]

Hello,

I have some more information on this issue. It seems that conversion is happening twice due to it happening in the price classes e.g. RegularPrice.php which gets cached via a class variable and it is also happening when getting the JSON config for the price box (\Magento\Catalog\Block\Product\View::getJsonConfig).

My fix for this was simply to create an after plugin for getJsonConfig and to modify the price amounts that are returned to not be converted again.