1 files changed, 343 insertions, 0 deletions

diff --git a/crates/ide_assists/src/handlers/merge_imports.rs b/crates/ide_assists/src/handlers/merge_imports.rs
new file mode 100644
index 000000000..7bd7e1e36
--- /dev/null
+++ b/crates/ide_assists/src/handlers/merge_imports.rs
@@ -0,0 +1,343 @@
+use ide_db::helpers::insert_use::{try_merge_imports, try_merge_trees, MergeBehavior};
+use syntax::{
+    algo::{neighbor, SyntaxRewriter},
+    ast, AstNode,
+};
+
+use crate::{
+    assist_context::{AssistContext, Assists},
+    utils::next_prev,
+    AssistId, AssistKind,
+};
+
+// Assist: merge_imports
+//
+// Merges two imports with a common prefix.
+//
+// ```
+// use std::$0fmt::Formatter;
+// use std::io;
+// ```
+// ->
+// ```
+// use std::{fmt::Formatter, io};
+// ```
+pub(crate) fn merge_imports(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let tree: ast::UseTree = ctx.find_node_at_offset()?;
+    let mut rewriter = SyntaxRewriter::default();
+    let mut offset = ctx.offset();
+
+    if let Some(use_item) = tree.syntax().parent().and_then(ast::Use::cast) {
+        let (merged, to_delete) =
+            next_prev().filter_map(|dir| neighbor(&use_item, dir)).find_map(|use_item2| {
+                try_merge_imports(&use_item, &use_item2, MergeBehavior::Full).zip(Some(use_item2))
+            })?;
+
+        rewriter.replace_ast(&use_item, &merged);
+        rewriter += to_delete.remove();
+
+        if to_delete.syntax().text_range().end() < offset {
+            offset -= to_delete.syntax().text_range().len();
+        }
+    } else {
+        let (merged, to_delete) =
+            next_prev().filter_map(|dir| neighbor(&tree, dir)).find_map(|use_tree| {
+                try_merge_trees(&tree, &use_tree, MergeBehavior::Full).zip(Some(use_tree))
+            })?;
+
+        rewriter.replace_ast(&tree, &merged);
+        rewriter += to_delete.remove();
+
+        if to_delete.syntax().text_range().end() < offset {
+            offset -= to_delete.syntax().text_range().len();
+        }
+    };
+
+    let target = tree.syntax().text_range();
+    acc.add(
+        AssistId("merge_imports", AssistKind::RefactorRewrite),
+        "Merge imports",
+        target,
+        |builder| {
+            builder.rewrite(rewriter);
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    #[test]
+    fn test_merge_equal() {
+        check_assist(
+            merge_imports,
+            r"
+use std::fmt$0::{Display, Debug};
+use std::fmt::{Display, Debug};
+",
+            r"
+use std::fmt::{Debug, Display};
+",
+        )
+    }
+
+    #[test]
+    fn test_merge_first() {
+        check_assist(
+            merge_imports,
+            r"
+use std::fmt$0::Debug;
+use std::fmt::Display;
+",
+            r"
+use std::fmt::{Debug, Display};
+",
+        )
+    }
+
+    #[test]
+    fn test_merge_second() {
+        check_assist(
+            merge_imports,
+            r"
+use std::fmt::Debug;
+use std::fmt$0::Display;
+",
+            r"
+use std::fmt::{Debug, Display};
+",
+        );
+    }
+
+    #[test]
+    fn merge_self1() {
+        check_assist(
+            merge_imports,
+            r"
+use std::fmt$0;
+use std::fmt::Display;
+",
+            r"
+use std::fmt::{self, Display};
+",
+        );
+    }
+
+    #[test]
+    fn merge_self2() {
+        check_assist(
+            merge_imports,
+            r"
+use std::{fmt, $0fmt::Display};
+",
+            r"
+use std::{fmt::{self, Display}};
+",
+        );
+    }
+
+    #[test]
+    fn skip_pub1() {
+        check_assist_not_applicable(
+            merge_imports,
+            r"
+pub use std::fmt$0::Debug;
+use std::fmt::Display;
+",
+        );
+    }
+
+    #[test]
+    fn skip_pub_last() {
+        check_assist_not_applicable(
+            merge_imports,
+            r"
+use std::fmt$0::Debug;
+pub use std::fmt::Display;
+",
+        );
+    }
+
+    #[test]
+    fn skip_pub_crate_pub() {
+        check_assist_not_applicable(
+            merge_imports,
+            r"
+pub(crate) use std::fmt$0::Debug;
+pub use std::fmt::Display;
+",
+        );
+    }
+
+    #[test]
+    fn skip_pub_pub_crate() {
+        check_assist_not_applicable(
+            merge_imports,
+            r"
+pub use std::fmt$0::Debug;
+pub(crate) use std::fmt::Display;
+",
+        );
+    }
+
+    #[test]
+    fn merge_pub() {
+        check_assist(
+            merge_imports,
+            r"
+pub use std::fmt$0::Debug;
+pub use std::fmt::Display;
+",
+            r"
+pub use std::fmt::{Debug, Display};
+",
+        )
+    }
+
+    #[test]
+    fn merge_pub_crate() {
+        check_assist(
+            merge_imports,
+            r"
+pub(crate) use std::fmt$0::Debug;
+pub(crate) use std::fmt::Display;
+",
+            r"
+pub(crate) use std::fmt::{Debug, Display};
+",
+        )
+    }
+
+    #[test]
+    fn test_merge_nested() {
+        check_assist(
+            merge_imports,
+            r"
+use std::{fmt$0::Debug, fmt::Display};
+",
+            r"
+use std::{fmt::{Debug, Display}};
+",
+        );
+    }
+
+    #[test]
+    fn test_merge_nested2() {
+        check_assist(
+            merge_imports,
+            r"
+use std::{fmt::Debug, fmt$0::Display};
+",
+            r"
+use std::{fmt::{Debug, Display}};
+",
+        );
+    }
+
+    #[test]
+    fn test_merge_single_wildcard_diff_prefixes() {
+        check_assist(
+            merge_imports,
+            r"
+use std$0::cell::*;
+use std::str;
+",
+            r"
+use std::{cell::*, str};
+",
+        )
+    }
+
+    #[test]
+    fn test_merge_both_wildcard_diff_prefixes() {
+        check_assist(
+            merge_imports,
+            r"
+use std$0::cell::*;
+use std::str::*;
+",
+            r"
+use std::{cell::*, str::*};
+",
+        )
+    }
+
+    #[test]
+    fn removes_just_enough_whitespace() {
+        check_assist(
+            merge_imports,
+            r"
+use foo$0::bar;
+use foo::baz;
+
+/// Doc comment
+",
+            r"
+use foo::{bar, baz};
+
+/// Doc comment
+",
+        );
+    }
+
+    #[test]
+    fn works_with_trailing_comma() {
+        check_assist(
+            merge_imports,
+            r"
+use {
+    foo$0::bar,
+    foo::baz,
+};
+",
+            r"
+use {
+    foo::{bar, baz},
+};
+",
+        );
+        check_assist(
+            merge_imports,
+            r"
+use {
+    foo::baz,
+    foo$0::bar,
+};
+",
+            r"
+use {
+    foo::{bar, baz},
+};
+",
+        );
+    }
+
+    #[test]
+    fn test_double_comma() {
+        check_assist(
+            merge_imports,
+            r"
+use foo::bar::baz;
+use foo::$0{
+    FooBar,
+};
+",
+            r"
+use foo::{FooBar, bar::baz};
+",
+        )
+    }
+
+    #[test]
+    fn test_empty_use() {
+        check_assist_not_applicable(
+            merge_imports,
+            r"
+use std::$0
+fn main() {}",
+        );
+    }
+}