1 files changed, 570 insertions, 0 deletions
diff --git a/src/tools/rust-analyzer/crates/ide-assists/src/handlers/merge_imports.rs b/src/tools/rust-analyzer/crates/ide-assists/src/handlers/merge_imports.rs
new file mode 100644
index 000000000..7e102ceba
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/ide-assists/src/handlers/merge_imports.rs
@@ -0,0 +1,570 @@
+use either::Either;
+use ide_db::imports::merge_imports::{try_merge_imports, try_merge_trees, MergeBehavior};
+use syntax::{algo::neighbor, ast, match_ast, ted, AstNode, SyntaxElement, SyntaxNode};
+
+use crate::{
+    assist_context::{AssistContext, Assists},
+    utils::next_prev,
+    AssistId, AssistKind,
+};
+
+use Edit::*;
+
+// 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 (target, edits) = if ctx.has_empty_selection() {
+        // Merge a neighbor
+        let tree: ast::UseTree = ctx.find_node_at_offset()?;
+        let target = tree.syntax().text_range();
+
+        let edits = if let Some(use_item) = tree.syntax().parent().and_then(ast::Use::cast) {
+            let mut neighbor = next_prev().find_map(|dir| neighbor(&use_item, dir)).into_iter();
+            use_item.try_merge_from(&mut neighbor)
+        } else {
+            let mut neighbor = next_prev().find_map(|dir| neighbor(&tree, dir)).into_iter();
+            tree.try_merge_from(&mut neighbor)
+        };
+        (target, edits?)
+    } else {
+        // Merge selected
+        let selection_range = ctx.selection_trimmed();
+        let parent_node = match ctx.covering_element() {
+            SyntaxElement::Node(n) => n,
+            SyntaxElement::Token(t) => t.parent()?,
+        };
+        let mut selected_nodes =
+            parent_node.children().filter(|it| selection_range.contains_range(it.text_range()));
+
+        let first_selected = selected_nodes.next()?;
+        let edits = match_ast! {
+            match first_selected {
+                ast::Use(use_item) => {
+                    use_item.try_merge_from(&mut selected_nodes.filter_map(ast::Use::cast))
+                },
+                ast::UseTree(use_tree) => {
+                    use_tree.try_merge_from(&mut selected_nodes.filter_map(ast::UseTree::cast))
+                },
+                _ => return None,
+            }
+        };
+        (selection_range, edits?)
+    };
+
+    acc.add(
+        AssistId("merge_imports", AssistKind::RefactorRewrite),
+        "Merge imports",
+        target,
+        |builder| {
+            let edits_mut: Vec<Edit> = edits
+                .into_iter()
+                .map(|it| match it {
+                    Remove(Either::Left(it)) => Remove(Either::Left(builder.make_mut(it))),
+                    Remove(Either::Right(it)) => Remove(Either::Right(builder.make_mut(it))),
+                    Replace(old, new) => Replace(builder.make_syntax_mut(old), new),
+                })
+                .collect();
+            for edit in edits_mut {
+                match edit {
+                    Remove(it) => it.as_ref().either(ast::Use::remove, ast::UseTree::remove),
+                    Replace(old, new) => ted::replace(old, new),
+                }
+            }
+        },
+    )
+}
+
+trait Merge: AstNode + Clone {
+    fn try_merge_from(self, items: &mut dyn Iterator<Item = Self>) -> Option<Vec<Edit>> {
+        let mut edits = Vec::new();
+        let mut merged = self.clone();
+        while let Some(item) = items.next() {
+            merged = merged.try_merge(&item)?;
+            edits.push(Edit::Remove(item.into_either()));
+        }
+        if !edits.is_empty() {
+            edits.push(Edit::replace(self, merged));
+            Some(edits)
+        } else {
+            None
+        }
+    }
+    fn try_merge(&self, other: &Self) -> Option<Self>;
+    fn into_either(self) -> Either<ast::Use, ast::UseTree>;
+}
+
+impl Merge for ast::Use {
+    fn try_merge(&self, other: &Self) -> Option<Self> {
+        try_merge_imports(self, other, MergeBehavior::Crate)
+    }
+    fn into_either(self) -> Either<ast::Use, ast::UseTree> {
+        Either::Left(self)
+    }
+}
+
+impl Merge for ast::UseTree {
+    fn try_merge(&self, other: &Self) -> Option<Self> {
+        try_merge_trees(self, other, MergeBehavior::Crate)
+    }
+    fn into_either(self) -> Either<ast::Use, ast::UseTree> {
+        Either::Right(self)
+    }
+}
+
+enum Edit {
+    Remove(Either<ast::Use, ast::UseTree>),
+    Replace(SyntaxNode, SyntaxNode),
+}
+
+impl Edit {
+    fn replace(old: impl AstNode, new: impl AstNode) -> Self {
+        Edit::Replace(old.syntax().clone(), new.syntax().clone())
+    }
+}
+
+#[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::{Display, Debug};
+",
+        )
+    }
+
+    #[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::{Display, Debug};
+",
+        );
+    }
+
+    #[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::{Display, self}};
+",
+        );
+    }
+
+    #[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 merge_pub_in_path_crate() {
+        check_assist(
+            merge_imports,
+            r"
+pub(in this::path) use std::fmt$0::Debug;
+pub(in this::path) use std::fmt::Display;
+",
+            r"
+pub(in this::path) 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::{Display, Debug}};
+",
+        );
+    }
+
+    #[test]
+    fn test_merge_with_nested_self_item() {
+        check_assist(
+            merge_imports,
+            r"
+use std$0::{fmt::{Write, Display}};
+use std::{fmt::{self, Debug}};
+",
+            r"
+use std::{fmt::{Write, Display, self, Debug}};
+",
+        );
+    }
+
+    #[test]
+    fn test_merge_with_nested_self_item2() {
+        check_assist(
+            merge_imports,
+            r"
+use std$0::{fmt::{self, Debug}};
+use std::{fmt::{Write, Display}};
+",
+            r"
+use std::{fmt::{self, Debug, Write, Display}};
+",
+        );
+    }
+
+    #[test]
+    fn test_merge_self_with_nested_self_item() {
+        check_assist(
+            merge_imports,
+            r"
+use std::{fmt$0::{self, Debug}, fmt::{Write, Display}};
+",
+            r"
+use std::{fmt::{self, Debug, Write, Display}};
+",
+        );
+    }
+
+    #[test]
+    fn test_merge_nested_self_and_empty() {
+        check_assist(
+            merge_imports,
+            r"
+use foo::$0{bar::{self}};
+use foo::{bar};
+",
+            r"
+use foo::{bar::{self}};
+",
+        )
+    }
+
+    #[test]
+    fn test_merge_nested_empty_and_self() {
+        check_assist(
+            merge_imports,
+            r"
+use foo::$0{bar};
+use foo::{bar::{self}};
+",
+            r"
+use foo::{bar::{self}};
+",
+        )
+    }
+
+    #[test]
+    fn test_merge_nested_list_self_and_glob() {
+        check_assist(
+            merge_imports,
+            r"
+use std$0::{fmt::*};
+use std::{fmt::{self, Display}};
+",
+            r"
+use std::{fmt::{*, self, 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() {}",
+        );
+    }
+
+    #[test]
+    fn split_glob() {
+        check_assist(
+            merge_imports,
+            r"
+use foo::$0*;
+use foo::bar::Baz;
+",
+            r"
+use foo::{*, bar::Baz};
+",
+        );
+    }
+
+    #[test]
+    fn merge_selection_uses() {
+        check_assist(
+            merge_imports,
+            r"
+use std::fmt::Error;
+$0use std::fmt::Display;
+use std::fmt::Debug;
+use std::fmt::Write;
+$0use std::fmt::Result;
+",
+            r"
+use std::fmt::Error;
+use std::fmt::{Display, Debug, Write};
+use std::fmt::Result;
+",
+        );
+    }
+
+    #[test]
+    fn merge_selection_use_trees() {
+        check_assist(
+            merge_imports,
+            r"
+use std::{
+    fmt::Error,
+    $0fmt::Display,
+    fmt::Debug,
+    fmt::Write,$0
+    fmt::Result,
+};",
+            r"
+use std::{
+    fmt::Error,
+    fmt::{Display, Debug, Write},
+    fmt::Result,
+};",
+        );
+        // FIXME: Remove redundant braces. See also unnecessary-braces diagnostic.
+        check_assist(
+            merge_imports,
+            r"use std::$0{fmt::Display, fmt::Debug}$0;",
+            r"use std::{fmt::{Display, Debug}};",
+        );
+    }
+}