Angular v13 Sass issue (SassError: Can't find stylesheet to import)

Hello, I have recently updated @mat-datetimepicker/core to v9.0.2 and I’m getting following error from sass-loader (Note: The build is working with v7.0.1).

Error

./src/styles.scss.webpack[javascript/auto]!=!./node_modules/css-loader/dist/cjs.js??ruleSet[1].rules[6].rules[0].oneOf[0].use[1]!./node_modules/postcss-loader/dist/cjs.js??ruleSet[1].rules[6].rules[0].oneOf[0].use[2]!./node_modules/resolve-url-loader/index.js??ruleSet[1].rules[6].rules[1].use[0]!./node_modules/sass-loader/dist/cjs.js??ruleSet[1].rules[6].rules[1].use[1]!./src/styles.scss - Error: Module build failed (from ./node_modules/sass-loader/dist/cjs.js):
SassError: Can't find stylesheet to import.
  ╷
6 │ @import "~@mat-datetimepicker/core/datetimepicker/datetimepicker-theme.scss";
  │         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  ╵
  src/theme/_angular.scss 6:9  @import
  src/theme/_main.scss 1:9     @import
  src/styles.scss 1:9          root stylesheet

./src/styles.scss - Error: Module build failed (from ./node_modules/mini-css-extract-plugin/dist/loader.js):
HookWebpackError: Module build failed (from ./node_modules/sass-loader/dist/cjs.js):
SassError: Can't find stylesheet to import.

Version

     _                      _                 ____ _     ___
    / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
   / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
  / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
 /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
                |___/


Angular CLI: 13.1.2
Node: 12.22.1
Package Manager: npm 6.14.12
OS: win32 x64

Angular: 13.1.1
... animations, cdk, common, compiler, compiler-cli, core, forms
... localize, material, material-moment-adapter
... platform-browser, platform-browser-dynamic, router

Package                         Version
---------------------------------------------------------       
@angular-devkit/architect       0.1301.2
@angular-devkit/build-angular   13.1.2
@angular-devkit/core            13.1.2
@angular-devkit/schematics      13.1.2
@angular/cli                    13.1.2
@angular/flex-layout            13.0.0-beta.36
@schematics/angular             13.1.2
rxjs                            7.5.1
typescript                      4.5.4

I don’t know what is causing this issue, you will find below my styles.scss:

@use '@angular/material' as mat;

@import "~@mat-datetimepicker/core/datetimepicker/datetimepicker-theme.scss";

@include mat.core();

@include mat-datetimepicker-theme($app-light-theme);
@include mat.all-component-themes($app-light-theme);

[bbortt]

@alexis-landrieu-avanade I’ve added the export flag and that seems to work (tested it using your sample)! fix released in v9.0.22. thanks much for your help.

[alexis-landrieu-avanade]

@bbortt I think the Theming part of the README.md file must be updated,

Theming

@use '@mat-datetimepicker/core/datetimepicker/datetimepicker-theme' as matdp;

// Using the $theme variable from the pre-built theme you can call the theming function
@include matdp.mat-datetimepicker-theme($theme);

@JorgeAlcarazKuv see full example