Flow doesn't trigger a new production bundle upon changes in imported CSS files

[mshabarov]

Description of the bug

Vaadin Flow builds a new production bundle if there is a change in frontend/themes/my-theme/styles.css:

Detected changed frontend files:
 - themes/my-theme/styles.css

In the same time, it doesn't build a bundle, when the changes are in the imported CSS file, e.g.:
themes/my-theme/styles.css:

@import url('./shared/layout.css');

and these changes are not reflected in the application.

Note: if an application uses a default pre-compiled prod bundle, the changes are reflected and added to a bundle.

Workaround: force production build or delete prod bundle from src/main/bundles/

Expected behavior

Production bundle should take into account changes in imported CSS files.

Minimal reproducible example

Any Flow application that requires a new production bundle.
themes/my-theme/styles.css:

@import url('./shared/layout.css');

themes/my-theme/shared/layout.css:

body {
    background-color: #ffff00;
}

Versions

• Vaadin / Flow version: 24.3.9 (and most likely later)