Upgrade to 2.1 breaks grunt theme fallback?

Question

Since the upgrade to 2.1 I get the following error on grunt exec:mytheme:

$ grunt exec:mytheme
Running "exec:mytheme" (exec) task
Running "clean:mytheme" (clean) task
>> 231 paths cleaned.

Done, without errors.


Execution Time (2016-06-27 18:20:12 UTC)
loading tasks                217ms  ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 70%
loading grunt-contrib-clean    4ms  ▇ 1%
clean:mytheme             88ms  ▇▇▇▇▇▇▇▇▇▇ 28%
Total 312ms

Processed Area: frontend, Locale: de_DE, Theme: Mytheme/default, File type: less.
>> [InvalidArgumentException]                                                                                                                                                      
>>   Verify entered values of the argument and options. Unable to get content for 'frontend/Mytheme/default/de_DE/Magento_Theme/css/source/module/_collapsible_navigation.less'
>> dev:source-theme:deploy [--type="..."] [--locale="..."] [--area="..."] [--theme="..."] [file1] ... [fileN]
>> Exited with code: 1.
Warning: Task "exec:mytheme" failed. Use --force to continue.

Aborted due to warnings.


Execution Time (2016-06-27 18:20:11 UTC)
loading tasks     281ms  ▇▇▇▇▇▇▇▇ 5%
exec:mytheme   5.7s  ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 95%
Total 6s

I did not overwrite _collapsible_navigation.less.

This is my themes.js for grunt:

'use strict';

/**
 * Define Themes
 *
 * area: area, one of (frontend|adminhtml|doc),
 * name: theme name in format Vendor/theme-name,
 * locale: locale,
 * files: [
 * 'css/styles-m',
 * 'css/styles-l'
 * ],
 * dsl: dynamic stylesheet language (less|sass)
 *
 */
module.exports = {
      blank: {
          area: 'frontend',
          name: 'Magento/blank',
          locale: 'en_US',
          files: [
              'css/styles-m',
              'css/styles-l',
              'css/email',
              'css/email-inline'
          ],
          dsl: 'less'
      },
      luma: {
          area: 'frontend',
          name: 'Magento/luma',
          locale: 'en_US',
          files: [
              'css/styles-m',
              'css/styles-l'
          ],
          dsl: 'less'
      },
      backend: {
          area: 'adminhtml',
          name: 'Magento/backend',
          locale: 'en_US',
          files: [
              'css/styles-old',
              'css/styles'
          ],
          dsl: 'less'
      },
      mytheme: {
          area: 'frontend',
          name: 'Mytheme/default',
          locale: 'de_DE',
          files: [
              'css/styles-m',
              'css/styles-l'
          ],
          dsl: 'less'
      }
};

Edit

There is a @import 'module/_collapsible_navigation.less'; in app/design/frontend/Mytheme/default/Magento_Theme/web/css/source/_module.less and I did not copy the _collapsible_navigation.less - but I think it should be loaded via the fallback system from Luma (as it was before the upgrade).

If I copy the module/_collapsible_navigation.less to my theme, it works.

Is this intended?

Answer 1

I was able to fix the problem by using

//@magento_import 'module/_collapsible_navigation.less';

In my overwritten Magento_Theme/module.less

(found on http://inchoo.net/magento-2/css-preprocessing-in-magento-2/)

I have no clue, why a simple @import worked in Magento 2.0 though ..