1 files changed, 392 insertions, 0 deletions

diff --git a/crates/ide/src/move_item.rs b/crates/ide/src/move_item.rs
new file mode 100644
index 000000000..be62d008d
--- /dev/null
+++ b/crates/ide/src/move_item.rs
@@ -0,0 +1,392 @@
+use std::iter::once;
+
+use hir::Semantics;
+use ide_db::{base_db::FileRange, RootDatabase};
+use syntax::{algo, AstNode, NodeOrToken, SyntaxElement, SyntaxKind, SyntaxNode};
+use text_edit::{TextEdit, TextEditBuilder};
+
+pub enum Direction {
+    Up,
+    Down,
+}
+
+// Feature: Move Item
+//
+// Move item under cursor or selection up and down.
+//
+// |===
+// | Editor  | Action Name
+//
+// | VS Code | **Rust Analyzer: Move item up**
+// | VS Code | **Rust Analyzer: Move item down**
+// |===
+pub(crate) fn move_item(
+    db: &RootDatabase,
+    range: FileRange,
+    direction: Direction,
+) -> Option<TextEdit> {
+    let sema = Semantics::new(db);
+    let file = sema.parse(range.file_id);
+
+    let item = file.syntax().covering_element(range.range);
+    find_ancestors(item, direction)
+}
+
+fn find_ancestors(item: SyntaxElement, direction: Direction) -> Option<TextEdit> {
+    let movable = [
+        SyntaxKind::MATCH_ARM,
+        // https://github.com/intellij-rust/intellij-rust/blob/master/src/main/kotlin/org/rust/ide/actions/mover/RsStatementUpDownMover.kt
+        SyntaxKind::LET_STMT,
+        SyntaxKind::EXPR_STMT,
+        SyntaxKind::MATCH_EXPR,
+        // https://github.com/intellij-rust/intellij-rust/blob/master/src/main/kotlin/org/rust/ide/actions/mover/RsItemUpDownMover.kt
+        SyntaxKind::TRAIT,
+        SyntaxKind::IMPL,
+        SyntaxKind::MACRO_CALL,
+        SyntaxKind::MACRO_DEF,
+        SyntaxKind::STRUCT,
+        SyntaxKind::ENUM,
+        SyntaxKind::MODULE,
+        SyntaxKind::USE,
+        SyntaxKind::FN,
+        SyntaxKind::CONST,
+        SyntaxKind::TYPE_ALIAS,
+    ];
+
+    let root = match item {
+        NodeOrToken::Node(node) => node,
+        NodeOrToken::Token(token) => token.parent(),
+    };
+
+    let ancestor = once(root.clone())
+        .chain(root.ancestors())
+        .filter(|ancestor| movable.contains(&ancestor.kind()))
+        .max_by_key(|ancestor| kind_priority(ancestor.kind()))?;
+
+    move_in_direction(&ancestor, direction)
+}
+
+fn kind_priority(kind: SyntaxKind) -> i32 {
+    match kind {
+        SyntaxKind::MATCH_ARM => 4,
+
+        SyntaxKind::LET_STMT | SyntaxKind::EXPR_STMT | SyntaxKind::MATCH_EXPR => 3,
+
+        SyntaxKind::TRAIT
+        | SyntaxKind::IMPL
+        | SyntaxKind::MACRO_CALL
+        | SyntaxKind::MACRO_DEF
+        | SyntaxKind::STRUCT
+        | SyntaxKind::ENUM
+        | SyntaxKind::MODULE
+        | SyntaxKind::USE
+        | SyntaxKind::FN
+        | SyntaxKind::CONST
+        | SyntaxKind::TYPE_ALIAS => 2,
+
+        // Placeholder for items, that are non-movable, and filtered even before kind_priority call
+        _ => 1,
+    }
+}
+
+fn move_in_direction(node: &SyntaxNode, direction: Direction) -> Option<TextEdit> {
+    let sibling = match direction {
+        Direction::Up => node.prev_sibling(),
+        Direction::Down => node.next_sibling(),
+    }?;
+
+    Some(replace_nodes(&sibling, node))
+}
+
+fn replace_nodes(first: &SyntaxNode, second: &SyntaxNode) -> TextEdit {
+    let mut edit = TextEditBuilder::default();
+
+    algo::diff(first, second).into_text_edit(&mut edit);
+    algo::diff(second, first).into_text_edit(&mut edit);
+
+    edit.finish()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::fixture;
+    use expect_test::{expect, Expect};
+
+    use crate::Direction;
+
+    fn check(ra_fixture: &str, expect: Expect, direction: Direction) {
+        let (analysis, range) = fixture::range(ra_fixture);
+        let edit = analysis.move_item(range, direction).unwrap().unwrap_or_default();
+        let mut file = analysis.file_text(range.file_id).unwrap().to_string();
+        edit.apply(&mut file);
+        expect.assert_eq(&file);
+    }
+
+    #[test]
+    fn test_moves_match_arm_up() {
+        check(
+            r#"
+fn main() {
+    match true {
+        true => {
+            println!("Hello, world");
+        },
+        false =>$0$0 {
+            println!("Test");
+        }
+    };
+}
+            "#,
+            expect![[r#"
+fn main() {
+    match true {
+        false => {
+            println!("Test");
+        },
+        true => {
+            println!("Hello, world");
+        }
+    };
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_match_arm_down() {
+        check(
+            r#"
+fn main() {
+    match true {
+        true =>$0$0 {
+            println!("Hello, world");
+        },
+        false => {
+            println!("Test");
+        }
+    };
+}
+            "#,
+            expect![[r#"
+fn main() {
+    match true {
+        false => {
+            println!("Test");
+        },
+        true => {
+            println!("Hello, world");
+        }
+    };
+}
+            "#]],
+            Direction::Down,
+        );
+    }
+
+    #[test]
+    fn test_nowhere_to_move() {
+        check(
+            r#"
+fn main() {
+    match true {
+        true =>$0$0 {
+            println!("Hello, world");
+        },
+        false => {
+            println!("Test");
+        }
+    };
+}
+            "#,
+            expect![[r#"
+fn main() {
+    match true {
+        true => {
+            println!("Hello, world");
+        },
+        false => {
+            println!("Test");
+        }
+    };
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_moves_let_stmt_up() {
+        check(
+            r#"
+fn main() {
+    let test = 123;
+    let test2$0$0 = 456;
+}
+            "#,
+            expect![[r#"
+fn main() {
+    let test2 = 456;
+    let test = 123;
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_prioritizes_match_arm() {
+        check(
+            r#"
+fn main() {
+    match true {
+        true => {
+            let test = 123;$0$0
+            let test2 = 456;
+        },
+        false => {
+            println!("Test");
+        }
+    };
+}
+            "#,
+            expect![[r#"
+fn main() {
+    match true {
+        false => {
+            println!("Test");
+        },
+        true => {
+            let test = 123;
+            let test2 = 456;
+        }
+    };
+}
+            "#]],
+            Direction::Down,
+        );
+    }
+
+    #[test]
+    fn test_moves_expr_up() {
+        check(
+            r#"
+fn main() {
+    println!("Hello, world");
+    println!("All I want to say is...");$0$0
+}
+            "#,
+            expect![[r#"
+fn main() {
+    println!("All I want to say is...");
+    println!("Hello, world");
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_nowhere_to_move_stmt() {
+        check(
+            r#"
+fn main() {
+    println!("All I want to say is...");$0$0
+    println!("Hello, world");
+}
+            "#,
+            expect![[r#"
+fn main() {
+    println!("All I want to say is...");
+    println!("Hello, world");
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_move_item() {
+        check(
+            r#"
+fn main() {}
+
+fn foo() {}$0$0
+            "#,
+            expect![[r#"
+fn foo() {}
+
+fn main() {}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_move_impl_up() {
+        check(
+            r#"
+struct Yay;
+
+trait Wow {}
+
+impl Wow for Yay {}$0$0
+            "#,
+            expect![[r#"
+struct Yay;
+
+impl Wow for Yay {}
+
+trait Wow {}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_move_use_up() {
+        check(
+            r#"
+use std::vec::Vec;
+use std::collections::HashMap$0$0;
+            "#,
+            expect![[r#"
+use std::collections::HashMap;
+use std::vec::Vec;
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn moves_match_expr_up() {
+        check(
+            r#"
+fn main() {
+    let test = 123;
+
+    $0match test {
+        456 => {},
+        _ => {}
+    }$0;
+}
+            "#,
+            expect![[r#"
+fn main() {
+    match test {
+        456 => {},
+        _ => {}
+    };
+
+    let test = 123;
+}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn handles_empty_file() {
+        check(r#"$0$0"#, expect![[r#""#]], Direction::Up);
+    }
+}