Complete exported macros in #[macro_use($0)]

crates/ide-completion/src/completions/attribute.rs

@@ -26,6 +26,7 @@ mod cfg;
 mod derive;
 mod lint;
 mod repr;
+mod macro_use;
 
 pub(crate) use self::derive::complete_derive_path;
 
@@ -35,6 +36,7 @@ pub(crate) fn complete_known_attribute_input(
     ctx: &CompletionContext<'_>,
     &colon_prefix: &bool,
     fake_attribute_under_caret: &ast::Attr,
+    extern_crate: Option<&ast::ExternCrate>,
 ) -> Option<()> {
     let attribute = fake_attribute_under_caret;
     let name_ref = match attribute.path() {
@@ -66,6 +68,9 @@ pub(crate) fn complete_known_attribute_input(
             lint::complete_lint(acc, ctx, colon_prefix, &existing_lints, &lints);
         }
         "cfg" => cfg::complete_cfg(acc, ctx),
+        "macro_use" => {
+            macro_use::complete_macro_use(acc, ctx, extern_crate, &parse_tt_as_comma_sep_paths(tt)?)
+        }
         _ => (),
     }
     Some(())

crates/ide-completion/src/completions/attribute/macro_use.rs

@@ -0,0 +1,34 @@
+use hir::ModuleDef;
+use ide_db::SymbolKind;
+use syntax::ast;
+
+use crate::{context::CompletionContext, item::CompletionItem, Completions};
+
+pub(super) fn complete_macro_use(
+    acc: &mut Completions,
+    ctx: &CompletionContext<'_>,
+    extern_crate: Option<&ast::ExternCrate>,
+    existing_imports: &[ast::Path],
+) {
+    let Some(extern_crate) = extern_crate else { return };
+    let Some(extern_crate) = ctx.sema.to_def(extern_crate) else { return };
+    let Some(krate) = extern_crate.resolved_crate(ctx.db) else { return };
+
+    for mod_def in krate.root_module().declarations(ctx.db) {
+        if let ModuleDef::Macro(mac) = mod_def {
+            let mac_name = mac.name(ctx.db);
+            let Some(mac_name) = mac_name.as_str() else { continue };
+
+            let existing_import = existing_imports
+                .iter()
+                .filter_map(|p| p.as_single_name_ref())
+                .find(|n| n.text() == mac_name);
+            if existing_import.is_some() {
+                continue;
+            }
+
+            let item = CompletionItem::new(SymbolKind::Macro, ctx.source_range(), mac_name);
+            item.add_to(acc, ctx.db);
+        }
+    }
+}

crates/ide-completion/src/context.rs

@@ -371,6 +371,7 @@ pub(super) enum CompletionAnalysis {
     UnexpandedAttrTT {
         colon_prefix: bool,
         fake_attribute_under_caret: Option<ast::Attr>,
+        extern_crate: Option<ast::ExternCrate>,
     },
 }
 

crates/ide-completion/src/context/analysis.rs

@@ -254,11 +254,13 @@ fn analyze(
             {
                 let colon_prefix = previous_non_trivia_token(self_token.clone())
                     .map_or(false, |it| T![:] == it.kind());
+
                 CompletionAnalysis::UnexpandedAttrTT {
                     fake_attribute_under_caret: fake_ident_token
                         .parent_ancestors()
                         .find_map(ast::Attr::cast),
                     colon_prefix,
+                    extern_crate: p.ancestors().find_map(ast::ExternCrate::cast),
                 }
             } else {
                 return None;

crates/ide-completion/src/lib.rs

@@ -211,12 +211,14 @@ pub fn completions(
             CompletionAnalysis::UnexpandedAttrTT {
                 colon_prefix,
                 fake_attribute_under_caret: Some(attr),
+                extern_crate,
             } => {
                 completions::attribute::complete_known_attribute_input(
                     acc,
                     ctx,
                     colon_prefix,
                     attr,
+                    extern_crate.as_ref(),
                 );
             }
             CompletionAnalysis::UnexpandedAttrTT { .. } | CompletionAnalysis::String { .. } => (),

crates/ide-completion/src/tests/attribute.rs

@@ -1067,3 +1067,82 @@ mod repr {
         );
     }
 }
+
+mod macro_use {
+    use super::*;
+
+    #[test]
+    fn completes_macros() {
+        check(
+            r#"
+//- /dep.rs crate:dep
+#[macro_export]
+macro_rules! foo {
+    () => {};
+}
+
+#[macro_export]
+macro_rules! bar {
+    () => {};
+}
+
+//- /main.rs crate:main deps:dep
+#[macro_use($0)]
+extern crate dep;
+"#,
+            expect![[r#"
+                ma bar
+                ma foo
+            "#]],
+        )
+    }
+
+    #[test]
+    fn only_completes_exported_macros() {
+        check(
+            r#"
+//- /dep.rs crate:dep
+#[macro_export]
+macro_rules! foo {
+    () => {};
+}
+
+macro_rules! bar {
+    () => {};
+}
+
+//- /main.rs crate:main deps:dep
+#[macro_use($0)]
+extern crate dep;
+"#,
+            expect![[r#"
+                ma foo
+            "#]],
+        )
+    }
+
+    #[test]
+    fn does_not_completes_already_imported_macros() {
+        check(
+            r#"
+//- /dep.rs crate:dep
+#[macro_export]
+macro_rules! foo {
+    () => {};
+}
+
+#[macro_export]
+macro_rules! bar {
+    () => {};
+}
+
+//- /main.rs crate:main deps:dep
+#[macro_use(foo, $0)]
+extern crate dep;
+"#,
+            expect![[r#"
+                ma bar
+            "#]],
+        )
+    }
+}