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

[CNanninga]

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-cicd2]

All committers have signed the CLA.

[magento-engcom-team]

Hi @CNanninga. Thank you for your contribution
Here is some useful tips how you can test your changes using Magento test environment.
Add the comment under your pull request to deploy test or vanilla Magento instance:

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[magento-engcom-team]

@CNanninga thank you for contributing. Please accept Community Contributors team invitation here to gain extended permissions for this repository.

[CNanninga]

@magento-engcom-team - I followed the link, but didn't get any indication that an action was completed. (Just got redirected to the repository home page.)

[dmanners]

Hi @CNanninga I can see next to your name it now says 'Member' which is what the link should setup so it looks to have worked fine.

[magento-engcom-team]

Hi @CNanninga. Thank you for your contribution.
We will aim to release these changes as part of 2.2.8.
Please check the release notes for final confirmation.

Please, consider to port this solution to 2.3 release line.
You may use Porting tool to port commits automatically.