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Fine tuning token selection at given position

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oxalica 2023-10-19 11:21:55 +08:00
parent 1b6b4534b3
commit 26c5d73015
1 changed files with 23 additions and 14 deletions
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37
crates/syntax/src/lib.rs
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@ -128,34 +128,43 @@ macro_rules! match_ast {
}};
}
/// Pick the most meaningful token at given cursor offset.
/// Pick the most likely interested token at given cursor offset.
pub fn best_token_at_offset(node: &SyntaxNode, offset: TextSize) -> Option<SyntaxToken> {
fn score(tok: SyntaxKind) -> u8 {
match tok {
SyntaxKind::ERROR | SyntaxKind::SPACE => 0,
SyntaxKind::COMMENT => 1,
// Avoid returning sibling delimiters, which may be in another region.
// Sorted by the nesting level in AST.
// `{ ...;|b = ... }`
T![;] | T![,] => 2,
T![=] | T![:] | T![@] => 3,
T!['('] | T!['['] | T!['{'] | T!["${"] | T![')'] | T![']'] | T!['}'] => 4,
// The rest are mostly operators, including `.` and `?`.
k if k.is_punct() => 5,
// Literal parts.
T!['"'] | T!["''"] => 10,
SyntaxKind::PATH_START
| SyntaxKind::PATH_END
| SyntaxKind::PATH_FRAGMENT
| SyntaxKind::STRING_FRAGMENT => 2,
SyntaxKind::STRING_ESCAPE => 3,
k if k.is_punct() => 4,
k if k.is_keyword() => 5,
| SyntaxKind::STRING_FRAGMENT => 11,
SyntaxKind::STRING_ESCAPE => 12,
// Atoms.
k if k.is_keyword() => 13,
// IDENT, INT, and etc.
_ => 6,
_ => 14,
}
}
match node.token_at_offset(offset) {
TokenAtOffset::None => None,
TokenAtOffset::Single(tok) => Some(tok),
TokenAtOffset::Between(lhs, rhs) => {
// Slightly prefer RHS.
if score(lhs.kind()) > score(rhs.kind()) {
Some(lhs)
} else {
Some(rhs)
}
}
// Slightly prefer RHS for equal scores.
TokenAtOffset::Between(lhs, rhs) if score(lhs.kind()) > score(rhs.kind()) => Some(lhs),
TokenAtOffset::Between(_, rhs) => Some(rhs),
}
}