3 files changed, 616 insertions, 4 deletions

diff --git a/crates/ra_ide_api/src/join_lines.rs b/crates/ra_ide_api/src/join_lines.rs
new file mode 100644
index 000000000..d6274dc97
--- /dev/null
+++ b/crates/ra_ide_api/src/join_lines.rs
@@ -0,0 +1,588 @@
+use itertools::Itertools;
+use ra_syntax::{
+    SourceFile, TextRange, TextUnit, AstNode, SyntaxNode,
+    SyntaxKind::{self, WHITESPACE, COMMA, R_CURLY, R_PAREN, R_BRACK},
+    algo::{find_covering_node, non_trivia_sibling},
+    ast,
+    Direction,
+};
+use ra_fmt::{
+    compute_ws, extract_trivial_expression
+};
+use ra_text_edit::TextEditBuilder;
+use ra_ide_api_light::LocalEdit;
+
+pub fn join_lines(file: &SourceFile, range: TextRange) -> LocalEdit {
+    let range = if range.is_empty() {
+        let syntax = file.syntax();
+        let text = syntax.text().slice(range.start()..);
+        let pos = match text.find('\n') {
+            None => {
+                return LocalEdit {
+                    label: "join lines".to_string(),
+                    edit: TextEditBuilder::default().finish(),
+                    cursor_position: None,
+                };
+            }
+            Some(pos) => pos,
+        };
+        TextRange::offset_len(range.start() + pos, TextUnit::of_char('\n'))
+    } else {
+        range
+    };
+
+    let node = find_covering_node(file.syntax(), range);
+    let mut edit = TextEditBuilder::default();
+    for node in node.descendants() {
+        let text = match node.leaf_text() {
+            Some(text) => text,
+            None => continue,
+        };
+        let range = match range.intersection(&node.range()) {
+            Some(range) => range,
+            None => continue,
+        } - node.range().start();
+        for (pos, _) in text[range].bytes().enumerate().filter(|&(_, b)| b == b'\n') {
+            let pos: TextUnit = (pos as u32).into();
+            let off = node.range().start() + range.start() + pos;
+            if !edit.invalidates_offset(off) {
+                remove_newline(&mut edit, node, text.as_str(), off);
+            }
+        }
+    }
+
+    LocalEdit { label: "join lines".to_string(), edit: edit.finish(), cursor_position: None }
+}
+
+fn remove_newline(
+    edit: &mut TextEditBuilder,
+    node: &SyntaxNode,
+    node_text: &str,
+    offset: TextUnit,
+) {
+    if node.kind() != WHITESPACE || node_text.bytes().filter(|&b| b == b'\n').count() != 1 {
+        // The node is either the first or the last in the file
+        let suff = &node_text[TextRange::from_to(
+            offset - node.range().start() + TextUnit::of_char('\n'),
+            TextUnit::of_str(node_text),
+        )];
+        let spaces = suff.bytes().take_while(|&b| b == b' ').count();
+
+        edit.replace(TextRange::offset_len(offset, ((spaces + 1) as u32).into()), " ".to_string());
+        return;
+    }
+
+    // Special case that turns something like:
+    //
+    // ```
+    // my_function({<|>
+    //    <some-expr>
+    // })
+    // ```
+    //
+    // into `my_function(<some-expr>)`
+    if join_single_expr_block(edit, node).is_some() {
+        return;
+    }
+    // ditto for
+    //
+    // ```
+    // use foo::{<|>
+    //    bar
+    // };
+    // ```
+    if join_single_use_tree(edit, node).is_some() {
+        return;
+    }
+
+    // The node is between two other nodes
+    let prev = node.prev_sibling().unwrap();
+    let next = node.next_sibling().unwrap();
+    if is_trailing_comma(prev.kind(), next.kind()) {
+        // Removes: trailing comma, newline (incl. surrounding whitespace)
+        edit.delete(TextRange::from_to(prev.range().start(), node.range().end()));
+    } else if prev.kind() == COMMA && next.kind() == R_CURLY {
+        // Removes: comma, newline (incl. surrounding whitespace)
+        let space = if let Some(left) = prev.prev_sibling() { compute_ws(left, next) } else { " " };
+        edit.replace(
+            TextRange::from_to(prev.range().start(), node.range().end()),
+            space.to_string(),
+        );
+    } else if let (Some(_), Some(next)) = (ast::Comment::cast(prev), ast::Comment::cast(next)) {
+        // Removes: newline (incl. surrounding whitespace), start of the next comment
+        edit.delete(TextRange::from_to(
+            node.range().start(),
+            next.syntax().range().start() + TextUnit::of_str(next.prefix()),
+        ));
+    } else {
+        // Remove newline but add a computed amount of whitespace characters
+        edit.replace(node.range(), compute_ws(prev, next).to_string());
+    }
+}
+
+fn has_comma_after(node: &SyntaxNode) -> bool {
+    match non_trivia_sibling(node, Direction::Next) {
+        Some(n) => n.kind() == COMMA,
+        _ => false,
+    }
+}
+
+fn join_single_expr_block(edit: &mut TextEditBuilder, node: &SyntaxNode) -> Option<()> {
+    let block = ast::Block::cast(node.parent()?)?;
+    let block_expr = ast::BlockExpr::cast(block.syntax().parent()?)?;
+    let expr = extract_trivial_expression(block)?;
+
+    let block_range = block_expr.syntax().range();
+    let mut buf = expr.syntax().text().to_string();
+
+    // Match block needs to have a comma after the block
+    if let Some(match_arm) = block_expr.syntax().parent().and_then(ast::MatchArm::cast) {
+        if !has_comma_after(match_arm.syntax()) {
+            buf.push(',');
+        }
+    }
+
+    edit.replace(block_range, buf);
+
+    Some(())
+}
+
+fn join_single_use_tree(edit: &mut TextEditBuilder, node: &SyntaxNode) -> Option<()> {
+    let use_tree_list = ast::UseTreeList::cast(node.parent()?)?;
+    let (tree,) = use_tree_list.use_trees().collect_tuple()?;
+    edit.replace(use_tree_list.syntax().range(), tree.syntax().text().to_string());
+    Some(())
+}
+
+fn is_trailing_comma(left: SyntaxKind, right: SyntaxKind) -> bool {
+    match (left, right) {
+        (COMMA, R_PAREN) | (COMMA, R_BRACK) => true,
+        _ => false,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::test_utils::{assert_eq_text, check_action, extract_range};
+
+    use super::*;
+
+    fn check_join_lines(before: &str, after: &str) {
+        check_action(before, after, |file, offset| {
+            let range = TextRange::offset_len(offset, 0.into());
+            let res = join_lines(file, range);
+            Some(res)
+        })
+    }
+
+    #[test]
+    fn test_join_lines_comma() {
+        check_join_lines(
+            r"
+fn foo() {
+    <|>foo(1,
+    )
+}
+",
+            r"
+fn foo() {
+    <|>foo(1)
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_lambda_block() {
+        check_join_lines(
+            r"
+pub fn reparse(&self, edit: &AtomTextEdit) -> File {
+    <|>self.incremental_reparse(edit).unwrap_or_else(|| {
+        self.full_reparse(edit)
+    })
+}
+",
+            r"
+pub fn reparse(&self, edit: &AtomTextEdit) -> File {
+    <|>self.incremental_reparse(edit).unwrap_or_else(|| self.full_reparse(edit))
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_block() {
+        check_join_lines(
+            r"
+fn foo() {
+    foo(<|>{
+        92
+    })
+}",
+            r"
+fn foo() {
+    foo(<|>92)
+}",
+        );
+    }
+
+    #[test]
+    fn join_lines_adds_comma_for_block_in_match_arm() {
+        check_join_lines(
+            r"
+fn foo(e: Result<U, V>) {
+    match e {
+        Ok(u) => <|>{
+            u.foo()
+        }
+        Err(v) => v,
+    }
+}",
+            r"
+fn foo(e: Result<U, V>) {
+    match e {
+        Ok(u) => <|>u.foo(),
+        Err(v) => v,
+    }
+}",
+        );
+    }
+
+    #[test]
+    fn join_lines_keeps_comma_for_block_in_match_arm() {
+        // We already have a comma
+        check_join_lines(
+            r"
+fn foo(e: Result<U, V>) {
+    match e {
+        Ok(u) => <|>{
+            u.foo()
+        },
+        Err(v) => v,
+    }
+}",
+            r"
+fn foo(e: Result<U, V>) {
+    match e {
+        Ok(u) => <|>u.foo(),
+        Err(v) => v,
+    }
+}",
+        );
+
+        // comma with whitespace between brace and ,
+        check_join_lines(
+            r"
+fn foo(e: Result<U, V>) {
+    match e {
+        Ok(u) => <|>{
+            u.foo()
+        }    ,
+        Err(v) => v,
+    }
+}",
+            r"
+fn foo(e: Result<U, V>) {
+    match e {
+        Ok(u) => <|>u.foo()    ,
+        Err(v) => v,
+    }
+}",
+        );
+
+        // comma with newline between brace and ,
+        check_join_lines(
+            r"
+fn foo(e: Result<U, V>) {
+    match e {
+        Ok(u) => <|>{
+            u.foo()
+        }
+        ,
+        Err(v) => v,
+    }
+}",
+            r"
+fn foo(e: Result<U, V>) {
+    match e {
+        Ok(u) => <|>u.foo()
+        ,
+        Err(v) => v,
+    }
+}",
+        );
+    }
+
+    #[test]
+    fn join_lines_keeps_comma_with_single_arg_tuple() {
+        // A single arg tuple
+        check_join_lines(
+            r"
+fn foo() {
+    let x = (<|>{
+       4
+    },);
+}",
+            r"
+fn foo() {
+    let x = (<|>4,);
+}",
+        );
+
+        // single arg tuple with whitespace between brace and comma
+        check_join_lines(
+            r"
+fn foo() {
+    let x = (<|>{
+       4
+    }   ,);
+}",
+            r"
+fn foo() {
+    let x = (<|>4   ,);
+}",
+        );
+
+        // single arg tuple with newline between brace and comma
+        check_join_lines(
+            r"
+fn foo() {
+    let x = (<|>{
+       4
+    }
+    ,);
+}",
+            r"
+fn foo() {
+    let x = (<|>4
+    ,);
+}",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_use_items_left() {
+        // No space after the '{'
+        check_join_lines(
+            r"
+<|>use ra_syntax::{
+    TextUnit, TextRange,
+};",
+            r"
+<|>use ra_syntax::{TextUnit, TextRange,
+};",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_use_items_right() {
+        // No space after the '}'
+        check_join_lines(
+            r"
+use ra_syntax::{
+<|>    TextUnit, TextRange
+};",
+            r"
+use ra_syntax::{
+<|>    TextUnit, TextRange};",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_use_items_right_comma() {
+        // No space after the '}'
+        check_join_lines(
+            r"
+use ra_syntax::{
+<|>    TextUnit, TextRange,
+};",
+            r"
+use ra_syntax::{
+<|>    TextUnit, TextRange};",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_use_tree() {
+        check_join_lines(
+            r"
+use ra_syntax::{
+    algo::<|>{
+        find_leaf_at_offset,
+    },
+    ast,
+};",
+            r"
+use ra_syntax::{
+    algo::<|>find_leaf_at_offset,
+    ast,
+};",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_normal_comments() {
+        check_join_lines(
+            r"
+fn foo() {
+    // Hello<|>
+    // world!
+}
+",
+            r"
+fn foo() {
+    // Hello<|> world!
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_doc_comments() {
+        check_join_lines(
+            r"
+fn foo() {
+    /// Hello<|>
+    /// world!
+}
+",
+            r"
+fn foo() {
+    /// Hello<|> world!
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_mod_comments() {
+        check_join_lines(
+            r"
+fn foo() {
+    //! Hello<|>
+    //! world!
+}
+",
+            r"
+fn foo() {
+    //! Hello<|> world!
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_multiline_comments_1() {
+        check_join_lines(
+            r"
+fn foo() {
+    // Hello<|>
+    /* world! */
+}
+",
+            r"
+fn foo() {
+    // Hello<|> world! */
+}
+",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_multiline_comments_2() {
+        check_join_lines(
+            r"
+fn foo() {
+    // The<|>
+    /* quick
+    brown
+    fox! */
+}
+",
+            r"
+fn foo() {
+    // The<|> quick
+    brown
+    fox! */
+}
+",
+        );
+    }
+
+    fn check_join_lines_sel(before: &str, after: &str) {
+        let (sel, before) = extract_range(before);
+        let file = SourceFile::parse(&before);
+        let result = join_lines(&file, sel);
+        let actual = result.edit.apply(&before);
+        assert_eq_text!(after, &actual);
+    }
+
+    #[test]
+    fn test_join_lines_selection_fn_args() {
+        check_join_lines_sel(
+            r"
+fn foo() {
+    <|>foo(1,
+        2,
+        3,
+    <|>)
+}
+    ",
+            r"
+fn foo() {
+    foo(1, 2, 3)
+}
+    ",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_selection_struct() {
+        check_join_lines_sel(
+            r"
+struct Foo <|>{
+    f: u32,
+}<|>
+    ",
+            r"
+struct Foo { f: u32 }
+    ",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_selection_dot_chain() {
+        check_join_lines_sel(
+            r"
+fn foo() {
+    join(<|>type_params.type_params()
+            .filter_map(|it| it.name())
+            .map(|it| it.text())<|>)
+}",
+            r"
+fn foo() {
+    join(type_params.type_params().filter_map(|it| it.name()).map(|it| it.text()))
+}",
+        );
+    }
+
+    #[test]
+    fn test_join_lines_selection_lambda_block_body() {
+        check_join_lines_sel(
+            r"
+pub fn handle_find_matching_brace() {
+    params.offsets
+        .map(|offset| <|>{
+            world.analysis().matching_brace(&file, offset).unwrap_or(offset)
+        }<|>)
+        .collect();
+}",
+            r"
+pub fn handle_find_matching_brace() {
+    params.offsets
+        .map(|offset| world.analysis().matching_brace(&file, offset).unwrap_or(offset))
+        .collect();
+}",
+        );
+    }
+}
diff --git a/crates/ra_ide_api/src/lib.rs b/crates/ra_ide_api/src/lib.rs
index d6f63490d..9e76dabff 100644
--- a/crates/ra_ide_api/src/lib.rs
+++ b/crates/ra_ide_api/src/lib.rs
@@ -36,9 +36,12 @@ mod syntax_tree;
 mod line_index;
 mod folding_ranges;
 mod line_index_utils;
+mod join_lines;
 
 #[cfg(test)]
 mod marks;
+#[cfg(test)]
+mod test_utils;
 
 use std::sync::Arc;
 
@@ -276,10 +279,7 @@ impl Analysis {
     /// stuff like trailing commas.
     pub fn join_lines(&self, frange: FileRange) -> SourceChange {
         let file = self.db.parse(frange.file_id);
-        SourceChange::from_local_edit(
-            frange.file_id,
-            ra_ide_api_light::join_lines(&file, frange.range),
-        )
+        SourceChange::from_local_edit(frange.file_id, join_lines::join_lines(&file, frange.range))
     }
 
     /// Returns an edit which should be applied when opening a new line, fixing
diff --git a/crates/ra_ide_api/src/test_utils.rs b/crates/ra_ide_api/src/test_utils.rs
new file mode 100644
index 000000000..bfac0fce3
--- /dev/null
+++ b/crates/ra_ide_api/src/test_utils.rs
@@ -0,0 +1,24 @@
+use ra_syntax::{SourceFile, TextUnit};
+
+use crate::LocalEdit;
+pub use test_utils::*;
+
+pub fn check_action<F: Fn(&SourceFile, TextUnit) -> Option<LocalEdit>>(
+    before: &str,
+    after: &str,
+    f: F,
+) {
+    let (before_cursor_pos, before) = extract_offset(before);
+    let file = SourceFile::parse(&before);
+    let result = f(&file, before_cursor_pos).expect("code action is not applicable");
+    let actual = result.edit.apply(&before);
+    let actual_cursor_pos = match result.cursor_position {
+        None => result
+            .edit
+            .apply_to_offset(before_cursor_pos)
+            .expect("cursor position is affected by the edit"),
+        Some(off) => off,
+    };
+    let actual = add_cursor(&actual, actual_cursor_pos);
+    assert_eq_text!(after, &actual);
+}