[Forwardport] Fixed issue with lib-line-height mixin failing when value of 'normal'…

[mage2pratik]

Original Pull Request

#18168

Description

This fixes an issue with the lib-line-height LESS mixin that results in an error during compilation if a value of "normal" is passed in.

Issue Reproduction Steps

1. Introduce any LESS, in a theme or module file, that uses the mixin .lib-line-height with a value of "normal."
2. Compile LESS, whether with Grunt, with browser compilation in developer mode, or via a setup:static-content:deploy.
3. The following error is thrown during LESS compilation: "SyntaxError: Operation on an invalid type in …"

Alternate Reproduction Steps

A common scenario that will cause this is if the mixin .lib-inline-block-space-item is used without parameters, as "normal" is passed in as the default value for @_line-height, which is then passed to .lib-line-height.

Additional Information

This issue became more prominent/likely in 2.2.6, because previously the definition of .lib-inline-block-space-item used a simple "line-height: @_line-height" declaration, whereas now it calls .lib-line-height with the value.

The first definition of .lib-line-height - with the guard "when not (@heightValue = false) and not (ispercentage(@heightValue)" - is the one that is matched if "normal" is passed in. This definition uses the mixin .lib-font-size-value, which does mathematical calculations on the value that are not valid for a value of "normal."

Fix

Placed additional guards on the first definition of .lib-line-height so that it does not match the value of "normal," and added a new definition that matches this value, avoiding the .lib-font-size-value call.

[magento-engcom-team]

Hi @sidolov, thank you for the review.
ENGCOM-3100 has been created to process this Pull Request

[magento-engcom-team]

Hi @mage2pratik. Thank you for your contribution.
We will aim to release these changes as part of 2.3.1.
Please check the release notes for final confirmation.