# Silence the Sass @import deprecation for the Bootstrap import chain

- Status: accepted
- Date: 2026-04-26

## Context and Problem Statement

Bootstrap 5 relies on Sass's `@import` rule and `!default` variable overrides: our custom `_variable.scss` must be loaded before Bootstrap's `variables.scss` so that Bootstrap picks up our values via the `!default` mechanism. Dart Sass 1.80+ deprecates `@import` in favour of the `@use` module system. How should the deprecation be addressed?

## Decision Drivers

- Bootstrap 5's `!default` override mechanism is incompatible with `@use` module scopes — variables loaded via `@use` do not flow into Bootstrap's module scope.
- Other Dart Sass deprecations (`color.red/green/blue()`, global `if()`) were fixed properly.

## Considered Options

- Silence the `@import` deprecation via `angular.json`
- Migrate to `@use` with `@use "bootstrap" with (...)`
- Wait for Bootstrap 6

## Decision Outcome

Chosen option: "Silence the `@import` deprecation via `angular.json`", because the `@use` migration is blocked by Bootstrap 5's architecture and Bootstrap 6 (which adopts `@use` natively) is not yet released.

The deprecation is suppressed in `angular.json` via `stylePreprocessorOptions.sass.silenceDeprecations: ["import"]`. The existing `@import`-based Bootstrap loading chain is kept intact. All other Dart Sass deprecations are fixed properly.

### Positive Consequences

- Bootstrap customisation works correctly with no behaviour change.
- No risk of introducing regressions by attempting an incompatible migration now.

### Negative Consequences

- Deprecation is silenced rather than fixed. `@import` will be removed in Dart Sass 3.0.

## Pros and Cons of the Options

### Silence the `@import` deprecation

- Good, because no behaviour change — existing variable overrides continue to work.
- Bad, because the underlying issue is deferred, not resolved.

### Migrate to `@use` with `@use "bootstrap" with (...)`

- Good, because fully resolves the deprecation.
- Bad, because requires rewriting all Bootstrap variable overrides using `with ()` syntax — significant effort.
- Bad, because the `with ()` syntax has limitations compared to `!default` chaining.

### Wait for Bootstrap 6

- Good, because Bootstrap 6 adopts `@use` natively — migration path will be documented by the Bootstrap team.
- Bad, because Bootstrap 6 release date is unknown; deferring means living with the silenced warning.

## Links

- Related to [ADR 0003](0003-dual-ui-library-progressive-migration.md)
- Future action: when Bootstrap 6 is released with `@use` support, migrate the import chain, remove the `silenceDeprecations` entry, and supersede this ADR.
