Print a warning when importing Sass files (vercel/turborepo#4789)

### Description


![image](https://user-images.githubusercontent.com/1621758/235940115-a8958bbb-76df-4353-b3e7-231231960623.png)

### Testing Instructions

See [Next.js PR](#49151)

link WEB-981

crates/turbopack/src/lib.rs

@@ -54,6 +54,7 @@ pub mod rebase;
 pub mod resolve;
 pub mod resolve_options_context;
 pub mod transition;
+pub(crate) mod unsupported_sass;
 
 pub use turbopack_css as css;
 pub use turbopack_ecmascript as ecmascript;

crates/turbopack/src/resolve.rs

@@ -14,7 +14,10 @@ use turbopack_ecmascript::typescript::resolve::{
     apply_tsconfig_resolve_options, tsconfig, tsconfig_resolve_options,
 };
 
-use crate::resolve_options_context::ResolveOptionsContextVc;
+use crate::{
+    resolve_options_context::ResolveOptionsContextVc,
+    unsupported_sass::UnsupportedSassResolvePluginVc,
+};
 
 const NODE_EXTERNALS: [&str; 51] = [
     "assert",
@@ -109,6 +112,9 @@ async fn base_resolve_options(
     }
     let import_map = import_map.cell();
 
+    let mut plugins = opt.plugins.clone();
+    plugins.push(UnsupportedSassResolvePluginVc::new(root).as_resolve_plugin());
+
     Ok(ResolveOptions {
         extensions: if let Some(environment) = emulating {
             environment.resolve_extensions().await?.clone_value()
@@ -220,7 +226,7 @@ async fn base_resolve_options(
         },
         import_map: Some(import_map),
         resolved_map: opt.resolved_map,
-        plugins: opt.plugins.clone(),
+        plugins,
         ..Default::default()
     }
     .into())

crates/turbopack/src/unsupported_sass.rs

@@ -0,0 +1,90 @@
+//! TODO(WEB-741) Remove this file once Sass is supported.
+
+use anyhow::Result;
+use turbo_tasks::primitives::StringVc;
+use turbo_tasks_fs::{glob::GlobVc, FileSystemPathVc};
+use turbopack_core::{
+    issue::{Issue, IssueSeverity, IssueSeverityVc, IssueVc},
+    resolve::{
+        parse::RequestVc,
+        plugin::{ResolvePlugin, ResolvePluginConditionVc, ResolvePluginVc},
+        ResolveResultOptionVc,
+    },
+};
+
+/// Resolve plugins that warns when importing a sass file.
+#[turbo_tasks::value]
+pub(crate) struct UnsupportedSassResolvePlugin {
+    root: FileSystemPathVc,
+}
+
+#[turbo_tasks::value_impl]
+impl UnsupportedSassResolvePluginVc {
+    #[turbo_tasks::function]
+    pub fn new(root: FileSystemPathVc) -> Self {
+        UnsupportedSassResolvePlugin { root }.cell()
+    }
+}
+
+#[turbo_tasks::value_impl]
+impl ResolvePlugin for UnsupportedSassResolvePlugin {
+    #[turbo_tasks::function]
+    fn after_resolve_condition(&self) -> ResolvePluginConditionVc {
+        ResolvePluginConditionVc::new(self.root.root(), GlobVc::new("**/*.{sass,scss}"))
+    }
+
+    #[turbo_tasks::function]
+    async fn after_resolve(
+        &self,
+        fs_path: FileSystemPathVc,
+        context: FileSystemPathVc,
+        request: RequestVc,
+    ) -> Result<ResolveResultOptionVc> {
+        let extension = fs_path.extension().await?;
+        if ["sass", "scss"].iter().any(|ext| ext == &*extension) {
+            UnsupportedSassModuleIssue { context, request }
+                .cell()
+                .as_issue()
+                .emit();
+        }
+
+        Ok(ResolveResultOptionVc::none())
+    }
+}
+
+#[turbo_tasks::value(shared)]
+struct UnsupportedSassModuleIssue {
+    context: FileSystemPathVc,
+    request: RequestVc,
+}
+
+#[turbo_tasks::value_impl]
+impl Issue for UnsupportedSassModuleIssue {
+    #[turbo_tasks::function]
+    fn severity(&self) -> IssueSeverityVc {
+        IssueSeverity::Warning.into()
+    }
+
+    #[turbo_tasks::function]
+    fn category(&self) -> StringVc {
+        StringVc::cell("resolve".to_string())
+    }
+
+    #[turbo_tasks::function]
+    async fn title(&self) -> Result<StringVc> {
+        Ok(StringVc::cell(format!(
+            "Unsupported Sass request: {}",
+            self.request.await?.request().as_deref().unwrap_or("N/A")
+        )))
+    }
+
+    #[turbo_tasks::function]
+    fn context(&self) -> FileSystemPathVc {
+        self.context
+    }
+
+    #[turbo_tasks::function]
+    fn description(&self) -> StringVc {
+        StringVc::cell("Turbopack does not yet support importing Sass modules.".to_string())
+    }
+}