1 files changed, 490 insertions, 0 deletions

diff --git a/crates/ra_ide/src/typing.rs b/crates/ra_ide/src/typing.rs
new file mode 100644
index 000000000..21e5be9b3
--- /dev/null
+++ b/crates/ra_ide/src/typing.rs
@@ -0,0 +1,490 @@
+//! This module handles auto-magic editing actions applied together with users
+//! edits. For example, if the user typed
+//!
+//! ```text
+//!     foo
+//!         .bar()
+//!         .baz()
+//!     |   // <- cursor is here
+//! ```
+//!
+//! and types `.` next, we want to indent the dot.
+//!
+//! Language server executes such typing assists synchronously. That is, they
+//! block user's typing and should be pretty fast for this reason!
+
+use ra_db::{FilePosition, SourceDatabase};
+use ra_fmt::leading_indent;
+use ra_syntax::{
+    algo::find_node_at_offset,
+    ast::{self, AstToken},
+    AstNode, SmolStr, SourceFile,
+    SyntaxKind::*,
+    SyntaxToken, TextRange, TextUnit, TokenAtOffset,
+};
+use ra_text_edit::TextEdit;
+
+use crate::{db::RootDatabase, source_change::SingleFileChange, SourceChange, SourceFileEdit};
+
+pub(crate) fn on_enter(db: &RootDatabase, position: FilePosition) -> Option<SourceChange> {
+    let parse = db.parse(position.file_id);
+    let file = parse.tree();
+    let comment = file
+        .syntax()
+        .token_at_offset(position.offset)
+        .left_biased()
+        .and_then(ast::Comment::cast)?;
+
+    if comment.kind().shape.is_block() {
+        return None;
+    }
+
+    let prefix = comment.prefix();
+    let comment_range = comment.syntax().text_range();
+    if position.offset < comment_range.start() + TextUnit::of_str(prefix) + TextUnit::from(1) {
+        return None;
+    }
+
+    // Continuing non-doc line comments (like this one :) ) is annoying
+    if prefix == "//" && comment_range.end() == position.offset {
+        return None;
+    }
+
+    let indent = node_indent(&file, comment.syntax())?;
+    let inserted = format!("\n{}{} ", indent, prefix);
+    let cursor_position = position.offset + TextUnit::of_str(&inserted);
+    let edit = TextEdit::insert(position.offset, inserted);
+
+    Some(
+        SourceChange::source_file_edit(
+            "on enter",
+            SourceFileEdit { edit, file_id: position.file_id },
+        )
+        .with_cursor(FilePosition { offset: cursor_position, file_id: position.file_id }),
+    )
+}
+
+fn node_indent(file: &SourceFile, token: &SyntaxToken) -> Option<SmolStr> {
+    let ws = match file.syntax().token_at_offset(token.text_range().start()) {
+        TokenAtOffset::Between(l, r) => {
+            assert!(r == *token);
+            l
+        }
+        TokenAtOffset::Single(n) => {
+            assert!(n == *token);
+            return Some("".into());
+        }
+        TokenAtOffset::None => unreachable!(),
+    };
+    if ws.kind() != WHITESPACE {
+        return None;
+    }
+    let text = ws.text();
+    let pos = text.rfind('\n').map(|it| it + 1).unwrap_or(0);
+    Some(text[pos..].into())
+}
+
+pub(crate) const TRIGGER_CHARS: &str = ".=>";
+
+pub(crate) fn on_char_typed(
+    db: &RootDatabase,
+    position: FilePosition,
+    char_typed: char,
+) -> Option<SourceChange> {
+    assert!(TRIGGER_CHARS.contains(char_typed));
+    let file = &db.parse(position.file_id).tree();
+    assert_eq!(file.syntax().text().char_at(position.offset), Some(char_typed));
+    let single_file_change = on_char_typed_inner(file, position.offset, char_typed)?;
+    Some(single_file_change.into_source_change(position.file_id))
+}
+
+fn on_char_typed_inner(
+    file: &SourceFile,
+    offset: TextUnit,
+    char_typed: char,
+) -> Option<SingleFileChange> {
+    assert!(TRIGGER_CHARS.contains(char_typed));
+    match char_typed {
+        '.' => on_dot_typed(file, offset),
+        '=' => on_eq_typed(file, offset),
+        '>' => on_arrow_typed(file, offset),
+        _ => unreachable!(),
+    }
+}
+
+/// Returns an edit which should be applied after `=` was typed. Primarily,
+/// this works when adding `let =`.
+// FIXME: use a snippet completion instead of this hack here.
+fn on_eq_typed(file: &SourceFile, offset: TextUnit) -> Option<SingleFileChange> {
+    assert_eq!(file.syntax().text().char_at(offset), Some('='));
+    let let_stmt: ast::LetStmt = find_node_at_offset(file.syntax(), offset)?;
+    if let_stmt.has_semi() {
+        return None;
+    }
+    if let Some(expr) = let_stmt.initializer() {
+        let expr_range = expr.syntax().text_range();
+        if expr_range.contains(offset) && offset != expr_range.start() {
+            return None;
+        }
+        if file.syntax().text().slice(offset..expr_range.start()).contains_char('\n') {
+            return None;
+        }
+    } else {
+        return None;
+    }
+    let offset = let_stmt.syntax().text_range().end();
+    Some(SingleFileChange {
+        label: "add semicolon".to_string(),
+        edit: TextEdit::insert(offset, ";".to_string()),
+        cursor_position: None,
+    })
+}
+
+/// Returns an edit which should be applied when a dot ('.') is typed on a blank line, indenting the line appropriately.
+fn on_dot_typed(file: &SourceFile, offset: TextUnit) -> Option<SingleFileChange> {
+    assert_eq!(file.syntax().text().char_at(offset), Some('.'));
+    let whitespace =
+        file.syntax().token_at_offset(offset).left_biased().and_then(ast::Whitespace::cast)?;
+
+    let current_indent = {
+        let text = whitespace.text();
+        let newline = text.rfind('\n')?;
+        &text[newline + 1..]
+    };
+    let current_indent_len = TextUnit::of_str(current_indent);
+
+    // Make sure dot is a part of call chain
+    let field_expr = ast::FieldExpr::cast(whitespace.syntax().parent())?;
+    let prev_indent = leading_indent(field_expr.syntax())?;
+    let target_indent = format!("    {}", prev_indent);
+    let target_indent_len = TextUnit::of_str(&target_indent);
+    if current_indent_len == target_indent_len {
+        return None;
+    }
+
+    Some(SingleFileChange {
+        label: "reindent dot".to_string(),
+        edit: TextEdit::replace(
+            TextRange::from_to(offset - current_indent_len, offset),
+            target_indent,
+        ),
+        cursor_position: Some(
+            offset + target_indent_len - current_indent_len + TextUnit::of_char('.'),
+        ),
+    })
+}
+
+/// Adds a space after an arrow when `fn foo() { ... }` is turned into `fn foo() -> { ... }`
+fn on_arrow_typed(file: &SourceFile, offset: TextUnit) -> Option<SingleFileChange> {
+    let file_text = file.syntax().text();
+    assert_eq!(file_text.char_at(offset), Some('>'));
+    let after_arrow = offset + TextUnit::of_char('>');
+    if file_text.char_at(after_arrow) != Some('{') {
+        return None;
+    }
+    if find_node_at_offset::<ast::RetType>(file.syntax(), offset).is_none() {
+        return None;
+    }
+
+    Some(SingleFileChange {
+        label: "add space after return type".to_string(),
+        edit: TextEdit::insert(after_arrow, " ".to_string()),
+        cursor_position: Some(after_arrow),
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use test_utils::{add_cursor, assert_eq_text, extract_offset};
+
+    use crate::mock_analysis::single_file;
+
+    use super::*;
+
+    #[test]
+    fn test_on_enter() {
+        fn apply_on_enter(before: &str) -> Option<String> {
+            let (offset, before) = extract_offset(before);
+            let (analysis, file_id) = single_file(&before);
+            let result = analysis.on_enter(FilePosition { offset, file_id }).unwrap()?;
+
+            assert_eq!(result.source_file_edits.len(), 1);
+            let actual = result.source_file_edits[0].edit.apply(&before);
+            let actual = add_cursor(&actual, result.cursor_position.unwrap().offset);
+            Some(actual)
+        }
+
+        fn do_check(before: &str, after: &str) {
+            let actual = apply_on_enter(before).unwrap();
+            assert_eq_text!(after, &actual);
+        }
+
+        fn do_check_noop(text: &str) {
+            assert!(apply_on_enter(text).is_none())
+        }
+
+        do_check(
+            r"
+/// Some docs<|>
+fn foo() {
+}
+",
+            r"
+/// Some docs
+/// <|>
+fn foo() {
+}
+",
+        );
+        do_check(
+            r"
+impl S {
+    /// Some<|> docs.
+    fn foo() {}
+}
+",
+            r"
+impl S {
+    /// Some
+    /// <|> docs.
+    fn foo() {}
+}
+",
+        );
+        do_check(
+            r"
+fn main() {
+    // Fix<|> me
+    let x = 1 + 1;
+}
+",
+            r"
+fn main() {
+    // Fix
+    // <|> me
+    let x = 1 + 1;
+}
+",
+        );
+        do_check_noop(
+            r"
+fn main() {
+    // Fix me<|>
+    let x = 1 + 1;
+}
+",
+        );
+
+        do_check_noop(r"<|>//! docz");
+    }
+
+    fn do_type_char(char_typed: char, before: &str) -> Option<(String, SingleFileChange)> {
+        let (offset, before) = extract_offset(before);
+        let edit = TextEdit::insert(offset, char_typed.to_string());
+        let before = edit.apply(&before);
+        let parse = SourceFile::parse(&before);
+        on_char_typed_inner(&parse.tree(), offset, char_typed)
+            .map(|it| (it.edit.apply(&before), it))
+    }
+
+    fn type_char(char_typed: char, before: &str, after: &str) {
+        let (actual, file_change) = do_type_char(char_typed, before)
+            .unwrap_or_else(|| panic!("typing `{}` did nothing", char_typed));
+
+        if after.contains("<|>") {
+            let (offset, after) = extract_offset(after);
+            assert_eq_text!(&after, &actual);
+            assert_eq!(file_change.cursor_position, Some(offset))
+        } else {
+            assert_eq_text!(after, &actual);
+        }
+    }
+
+    fn type_char_noop(char_typed: char, before: &str) {
+        let file_change = do_type_char(char_typed, before);
+        assert!(file_change.is_none())
+    }
+
+    #[test]
+    fn test_on_eq_typed() {
+        //     do_check(r"
+        // fn foo() {
+        //     let foo =<|>
+        // }
+        // ", r"
+        // fn foo() {
+        //     let foo =;
+        // }
+        // ");
+        type_char(
+            '=',
+            r"
+fn foo() {
+    let foo <|> 1 + 1
+}
+",
+            r"
+fn foo() {
+    let foo = 1 + 1;
+}
+",
+        );
+        //     do_check(r"
+        // fn foo() {
+        //     let foo =<|>
+        //     let bar = 1;
+        // }
+        // ", r"
+        // fn foo() {
+        //     let foo =;
+        //     let bar = 1;
+        // }
+        // ");
+    }
+
+    #[test]
+    fn indents_new_chain_call() {
+        type_char(
+            '.',
+            r"
+            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
+                self.child_impl(db, name)
+                <|>
+            }
+            ",
+            r"
+            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
+                self.child_impl(db, name)
+                    .
+            }
+            ",
+        );
+        type_char_noop(
+            '.',
+            r"
+            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
+                self.child_impl(db, name)
+                    <|>
+            }
+            ",
+        )
+    }
+
+    #[test]
+    fn indents_new_chain_call_with_semi() {
+        type_char(
+            '.',
+            r"
+            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
+                self.child_impl(db, name)
+                <|>;
+            }
+            ",
+            r"
+            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
+                self.child_impl(db, name)
+                    .;
+            }
+            ",
+        );
+        type_char_noop(
+            '.',
+            r"
+            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
+                self.child_impl(db, name)
+                    <|>;
+            }
+            ",
+        )
+    }
+
+    #[test]
+    fn indents_continued_chain_call() {
+        type_char(
+            '.',
+            r"
+            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
+                self.child_impl(db, name)
+                    .first()
+                <|>
+            }
+            ",
+            r"
+            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
+                self.child_impl(db, name)
+                    .first()
+                    .
+            }
+            ",
+        );
+        type_char_noop(
+            '.',
+            r"
+            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
+                self.child_impl(db, name)
+                    .first()
+                    <|>
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn indents_middle_of_chain_call() {
+        type_char(
+            '.',
+            r"
+            fn source_impl() {
+                let var = enum_defvariant_list().unwrap()
+                <|>
+                    .nth(92)
+                    .unwrap();
+            }
+            ",
+            r"
+            fn source_impl() {
+                let var = enum_defvariant_list().unwrap()
+                    .
+                    .nth(92)
+                    .unwrap();
+            }
+            ",
+        );
+        type_char_noop(
+            '.',
+            r"
+            fn source_impl() {
+                let var = enum_defvariant_list().unwrap()
+                    <|>
+                    .nth(92)
+                    .unwrap();
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn dont_indent_freestanding_dot() {
+        type_char_noop(
+            '.',
+            r"
+            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
+                <|>
+            }
+            ",
+        );
+        type_char_noop(
+            '.',
+            r"
+            pub fn child(&self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<Module>> {
+            <|>
+            }
+            ",
+        );
+    }
+
+    #[test]
+    fn adds_space_after_return_type() {
+        type_char('>', "fn foo() -<|>{ 92 }", "fn foo() -><|> { 92 }")
+    }
+}