1 files changed, 349 insertions, 0 deletions

diff --git a/crates/ra_syntax/src/parsing/reparsing.rs b/crates/ra_syntax/src/parsing/reparsing.rs
new file mode 100644
index 000000000..edf3fa291
--- /dev/null
+++ b/crates/ra_syntax/src/parsing/reparsing.rs
@@ -0,0 +1,349 @@
+use crate::{
+    SyntaxKind::*, TextRange, TextUnit,
+    algo,
+    syntax_node::{GreenNode, SyntaxNode},
+    syntax_error::SyntaxError,
+    parsing::{
+        grammar,
+        parser_impl,
+        builder::GreenBuilder,
+        parser_api::Parser,
+        lexer::{tokenize, Token},
+    }
+};
+
+use ra_text_edit::AtomTextEdit;
+
+pub(crate) fn incremental_reparse(
+    node: &SyntaxNode,
+    edit: &AtomTextEdit,
+    errors: Vec<SyntaxError>,
+) -> Option<(GreenNode, Vec<SyntaxError>)> {
+    let (node, green, new_errors) =
+        reparse_leaf(node, &edit).or_else(|| reparse_block(node, &edit))?;
+    let green_root = node.replace_with(green);
+    let errors = merge_errors(errors, new_errors, node, edit);
+    Some((green_root, errors))
+}
+
+fn reparse_leaf<'node>(
+    node: &'node SyntaxNode,
+    edit: &AtomTextEdit,
+) -> Option<(&'node SyntaxNode, GreenNode, Vec<SyntaxError>)> {
+    let node = algo::find_covering_node(node, edit.delete);
+    match node.kind() {
+        WHITESPACE | COMMENT | IDENT | STRING | RAW_STRING => {
+            let text = get_text_after_edit(node, &edit);
+            let tokens = tokenize(&text);
+            let token = match tokens[..] {
+                [token] if token.kind == node.kind() => token,
+                _ => return None,
+            };
+
+            if token.kind == IDENT && is_contextual_kw(&text) {
+                return None;
+            }
+
+            let green = GreenNode::new_leaf(node.kind(), text.into());
+            let new_errors = vec![];
+            Some((node, green, new_errors))
+        }
+        _ => None,
+    }
+}
+
+fn reparse_block<'node>(
+    node: &'node SyntaxNode,
+    edit: &AtomTextEdit,
+) -> Option<(&'node SyntaxNode, GreenNode, Vec<SyntaxError>)> {
+    let (node, reparser) = find_reparsable_node(node, edit.delete)?;
+    let text = get_text_after_edit(node, &edit);
+    let tokens = tokenize(&text);
+    if !is_balanced(&tokens) {
+        return None;
+    }
+    let (green, new_errors) =
+        parser_impl::parse_with(GreenBuilder::new(), &text, &tokens, reparser);
+    Some((node, green, new_errors))
+}
+
+fn get_text_after_edit(node: &SyntaxNode, edit: &AtomTextEdit) -> String {
+    let edit = AtomTextEdit::replace(edit.delete - node.range().start(), edit.insert.clone());
+    edit.apply(node.text().to_string())
+}
+
+fn is_contextual_kw(text: &str) -> bool {
+    match text {
+        "auto" | "default" | "union" => true,
+        _ => false,
+    }
+}
+
+fn find_reparsable_node(
+    node: &SyntaxNode,
+    range: TextRange,
+) -> Option<(&SyntaxNode, fn(&mut Parser))> {
+    let node = algo::find_covering_node(node, range);
+    node.ancestors().find_map(|node| grammar::reparser(node).map(|r| (node, r)))
+}
+
+fn is_balanced(tokens: &[Token]) -> bool {
+    if tokens.is_empty()
+        || tokens.first().unwrap().kind != L_CURLY
+        || tokens.last().unwrap().kind != R_CURLY
+    {
+        return false;
+    }
+    let mut balance = 0usize;
+    for t in tokens.iter() {
+        match t.kind {
+            L_CURLY => balance += 1,
+            R_CURLY => {
+                balance = match balance.checked_sub(1) {
+                    Some(b) => b,
+                    None => return false,
+                }
+            }
+            _ => (),
+        }
+    }
+    balance == 0
+}
+
+fn merge_errors(
+    old_errors: Vec<SyntaxError>,
+    new_errors: Vec<SyntaxError>,
+    old_node: &SyntaxNode,
+    edit: &AtomTextEdit,
+) -> Vec<SyntaxError> {
+    let mut res = Vec::new();
+    for e in old_errors {
+        if e.offset() <= old_node.range().start() {
+            res.push(e)
+        } else if e.offset() >= old_node.range().end() {
+            res.push(e.add_offset(TextUnit::of_str(&edit.insert) - edit.delete.len()));
+        }
+    }
+    for e in new_errors {
+        res.push(e.add_offset(old_node.range().start()));
+    }
+    res
+}
+
+#[cfg(test)]
+mod tests {
+    use test_utils::{extract_range, assert_eq_text};
+
+    use crate::{SourceFile, AstNode, utils::dump_tree};
+    use super::*;
+
+    fn do_check<F>(before: &str, replace_with: &str, reparser: F)
+    where
+        for<'a> F: Fn(
+            &'a SyntaxNode,
+            &AtomTextEdit,
+        ) -> Option<(&'a SyntaxNode, GreenNode, Vec<SyntaxError>)>,
+    {
+        let (range, before) = extract_range(before);
+        let edit = AtomTextEdit::replace(range, replace_with.to_owned());
+        let after = edit.apply(before.clone());
+
+        let fully_reparsed = SourceFile::parse(&after);
+        let incrementally_reparsed = {
+            let f = SourceFile::parse(&before);
+            let edit = AtomTextEdit { delete: range, insert: replace_with.to_string() };
+            let (node, green, new_errors) =
+                reparser(f.syntax(), &edit).expect("cannot incrementally reparse");
+            let green_root = node.replace_with(green);
+            let errors = super::merge_errors(f.errors(), new_errors, node, &edit);
+            SourceFile::new(green_root, errors)
+        };
+
+        assert_eq_text!(
+            &dump_tree(fully_reparsed.syntax()),
+            &dump_tree(incrementally_reparsed.syntax()),
+        )
+    }
+
+    #[test]
+    fn reparse_block_tests() {
+        let do_check = |before, replace_to| do_check(before, replace_to, reparse_block);
+
+        do_check(
+            r"
+fn foo() {
+    let x = foo + <|>bar<|>
+}
+",
+            "baz",
+        );
+        do_check(
+            r"
+fn foo() {
+    let x = foo<|> + bar<|>
+}
+",
+            "baz",
+        );
+        do_check(
+            r"
+struct Foo {
+    f: foo<|><|>
+}
+",
+            ",\n    g: (),",
+        );
+        do_check(
+            r"
+fn foo {
+    let;
+    1 + 1;
+    <|>92<|>;
+}
+",
+            "62",
+        );
+        do_check(
+            r"
+mod foo {
+    fn <|><|>
+}
+",
+            "bar",
+        );
+        do_check(
+            r"
+trait Foo {
+    type <|>Foo<|>;
+}
+",
+            "Output",
+        );
+        do_check(
+            r"
+impl IntoIterator<Item=i32> for Foo {
+    f<|><|>
+}
+",
+            "n next(",
+        );
+        do_check(
+            r"
+use a::b::{foo,<|>,bar<|>};
+    ",
+            "baz",
+        );
+        do_check(
+            r"
+pub enum A {
+    Foo<|><|>
+}
+",
+            "\nBar;\n",
+        );
+        do_check(
+            r"
+foo!{a, b<|><|> d}
+",
+            ", c[3]",
+        );
+        do_check(
+            r"
+fn foo() {
+    vec![<|><|>]
+}
+",
+            "123",
+        );
+        do_check(
+            r"
+extern {
+    fn<|>;<|>
+}
+",
+            " exit(code: c_int)",
+        );
+    }
+
+    #[test]
+    fn reparse_leaf_tests() {
+        let do_check = |before, replace_to| do_check(before, replace_to, reparse_leaf);
+
+        do_check(
+            r"<|><|>
+fn foo() -> i32 { 1 }
+",
+            "\n\n\n   \n",
+        );
+        do_check(
+            r"
+fn foo() -> <|><|> {}
+",
+            "  \n",
+        );
+        do_check(
+            r"
+fn <|>foo<|>() -> i32 { 1 }
+",
+            "bar",
+        );
+        do_check(
+            r"
+fn foo<|><|>foo() {  }
+",
+            "bar",
+        );
+        do_check(
+            r"
+fn foo /* <|><|> */ () {}
+",
+            "some comment",
+        );
+        do_check(
+            r"
+fn baz <|><|> () {}
+",
+            "    \t\t\n\n",
+        );
+        do_check(
+            r"
+fn baz <|><|> () {}
+",
+            "    \t\t\n\n",
+        );
+        do_check(
+            r"
+/// foo <|><|>omment
+mod { }
+",
+            "c",
+        );
+        do_check(
+            r#"
+fn -> &str { "Hello<|><|>" }
+"#,
+            ", world",
+        );
+        do_check(
+            r#"
+fn -> &str { // "Hello<|><|>"
+"#,
+            ", world",
+        );
+        do_check(
+            r##"
+fn -> &str { r#"Hello<|><|>"#
+"##,
+            ", world",
+        );
+        do_check(
+            r"
+#[derive(<|>Copy<|>)]
+enum Foo {
+
+}
+",
+            "Clone",
+        );
+    }
+}