Generated by SassMeister.com.

input.scss

@function button() {
    @return (
      id: 'mat-button',
      something: 'xxx',
    )
}

@mixin button-theme($theme) {
    .mat-button {
        color: blue;
    }
}


@mixin theme($theme, $components) {
    
    @each $component in $components {
        @if (map-get($component, 'id') == 'mat-button') {
            @include button-theme($theme);
        }
    }
}

app {
    background: black;
}

@include theme((), (
  button(),
))

output.css

app {
  background: black;
}

.mat-button {
  color: blue;
}

settings.json

{
  "sass": {
    "compiler": "dart-sass/1.32.12",
    "extensions": {},
    "syntax": "SCSS",
    "outputStyle": "expanded"
  },
  "autoprefixer": false
}