setup:static-content:deploy fails with errors which makes no sense

[Eddcapone]

Preconditions (*)

1. 2.4.1 (i had this bug with any version since I started with magento 2)

Steps to reproduce (*)

If I execute php bin/magento setup:static-content:deploy then I get alot of errors like:

Compilation from source: /home/company/staging.company.de/app/design/frontend/company/fresh/web/css/source/_mixins/fx.less
variable @theme__color__primary is undefined in file /home/company/staging.company.de/var/view_preprocessed/pub/static/frontend/company/fresh/de_DE/css/source/_mixins/fx.less in fx.less on line 3, column 12
1| .link_hover {
2|     cursor: pointer;
3|     color: @theme__color__primary;
4|     text-decoration: underline;
5|     text-decoration-color: @theme__color__primary;
6| }

It says that @theme__color__primary is undefined in the file fx.less,
so I checked if that is true:

This is my _extend.less file:

// Variables
@import 'lib/extend/variables/_layout';
@import 'lib/extend/variables/_colors';

@import '_variables/elements/button';
@import '_variables/responsive';
@import '_variables/icons';
@import '_variables/colors';                     // <-- @theme__color__primary is defined here
@import '_variables/header';
@import '_variables/typographie';
    // Extensions
    @import '_variables/amasty/checkout';

// Mixins
@import '_mixins/fonts';
@import '_mixins/fx';                            // <-- Error is getting thrown here
@import '_mixins/elements/button';

As you can see, the file _variables/colors.less which contains the variable is loaded before _mixins/fx.less, so why is the error thrown?

_variables/colors.less

@defaultBackgroundColor: #EFF1F2;
@color-company-orange-alt: #FF7712;
@theme__color__primary: @color-company-orange-alt; 

Expected result (*)

It should compile without errors

Actual result (*)

It throws errors.

---

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• Severity: S4 - Affects aesthetics, professional look and feel, “quality” or “usability”.

[m2-assistant]

Hi @Eddcapone. Thank you for your report.
To help us process this issue please make sure that you provided the following information:

• Summary of the issue
• Information on your environment
• Steps to reproduce
• Expected and actual results

Please make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce. To deploy vanilla Magento instance on our environment, please, add a comment to the issue:

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[Eddcapone]

If I am using grunt refresh in a environment with deploy mode set to developer , then it works without any errors. Why does it fail in production mode with php bin/magento setup:static-content:deploy -f ?

[hostep]

Does it fail on a particular theme? Maybe Magento/blank ?
I've seen failures like that which can happen when you try to use a variable defined in a custom theme from inside a module, then compiling the Magento/blank theme will break since it doesn't know that variable.

Magento's SCD command compiles your custom theme + its parent themes, so that could be a possible explanation here.
This behavior can be changed in Magento 2.4.2 btw, where you can specify a new --no-parent flag which got introduced by #30090

Not sure if this is helpful though, I'm not a frontend developer, so I might be mistaken here

[Eddcapone]

@hostep, I figured it out that the bug is related to the filename. I have to add an underscore _ in front of the files where the problem occurs. I am confused as why this is necessary and why I never had to do this when using grunt refresh.

So I changed _variables/colors.less to _variables/_colors.less and _mixins/fx to _mixins/_fx.less
Of course I also changed it in the file _extend.less

I am puzzled why the filename caused the bug, I was not able to find anything about it in the documentation.

I hope someone from the magento team can answer this, maybe the bug is unknown to them.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed after 14 days if no further activity occurs. Is this issue still relevant? If so, what is blocking it? Is there anything you can do to help move it forward? Thank you for your contributions!

[Eddcapone]

The question still remains. Where is the documentation for the underscore prefix for the style filename?