321 lines
10 KiB
Rust
321 lines
10 KiB
Rust
//! Syntax Tree library used throughout the rust analyzer.
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//!
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//! Properties:
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//! - easy and fast incremental re-parsing
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//! - graceful handling of errors
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//! - full-fidelity representation (*any* text can be precisely represented as
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//! a syntax tree)
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//!
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//! For more information, see the [RFC]. Current implementation is inspired by
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//! the [Swift] one.
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//!
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//! The most interesting modules here are `syntax_node` (which defines concrete
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//! syntax tree) and `ast` (which defines abstract syntax tree on top of the
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//! CST). The actual parser live in a separate `ra_parser` crate, though the
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//! lexer lives in this crate.
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//!
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//! See `api_walkthrough` test in this file for a quick API tour!
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//!
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//! [RFC]: <https://github.com/rust-lang/rfcs/pull/2256>
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//! [Swift]: <https://github.com/apple/swift/blob/13d593df6f359d0cb2fc81cfaac273297c539455/lib/Syntax/README.md>
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mod syntax_node;
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mod syntax_error;
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mod parsing;
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mod validation;
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mod ptr;
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#[cfg(test)]
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mod tests;
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pub mod algo;
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pub mod ast;
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#[doc(hidden)]
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pub mod fuzz;
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use std::{fmt::Write, marker::PhantomData, sync::Arc};
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use ra_text_edit::AtomTextEdit;
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use crate::syntax_node::GreenNode;
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pub use crate::{
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algo::InsertPosition,
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ast::{AstNode, AstToken},
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parsing::{classify_literal, tokenize, Token},
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ptr::{AstPtr, SyntaxNodePtr},
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syntax_error::{Location, SyntaxError, SyntaxErrorKind},
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syntax_node::{
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Direction, NodeOrToken, SyntaxElement, SyntaxNode, SyntaxToken, SyntaxTreeBuilder,
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},
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};
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pub use ra_parser::{SyntaxKind, T};
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pub use rowan::{SmolStr, SyntaxText, TextRange, TextUnit, TokenAtOffset, WalkEvent};
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/// `Parse` is the result of the parsing: a syntax tree and a collection of
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/// errors.
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///
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/// Note that we always produce a syntax tree, even for completely invalid
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/// files.
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#[derive(Debug, PartialEq, Eq)]
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pub struct Parse<T> {
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green: GreenNode,
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errors: Arc<Vec<SyntaxError>>,
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_ty: PhantomData<fn() -> T>,
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}
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impl<T> Clone for Parse<T> {
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fn clone(&self) -> Parse<T> {
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Parse { green: self.green.clone(), errors: self.errors.clone(), _ty: PhantomData }
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}
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}
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impl<T> Parse<T> {
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fn new(green: GreenNode, errors: Vec<SyntaxError>) -> Parse<T> {
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Parse { green, errors: Arc::new(errors), _ty: PhantomData }
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}
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pub fn syntax_node(&self) -> SyntaxNode {
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SyntaxNode::new_root(self.green.clone())
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}
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}
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impl<T: AstNode> Parse<T> {
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pub fn to_syntax(self) -> Parse<SyntaxNode> {
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Parse { green: self.green, errors: self.errors, _ty: PhantomData }
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}
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pub fn tree(&self) -> T {
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T::cast(self.syntax_node()).unwrap()
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}
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pub fn errors(&self) -> &[SyntaxError] {
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&*self.errors
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}
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pub fn ok(self) -> Result<T, Arc<Vec<SyntaxError>>> {
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if self.errors.is_empty() {
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Ok(self.tree())
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} else {
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Err(self.errors)
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}
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}
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}
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impl Parse<SyntaxNode> {
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pub fn cast<N: AstNode>(self) -> Option<Parse<N>> {
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if N::cast(self.syntax_node()).is_some() {
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Some(Parse { green: self.green, errors: self.errors, _ty: PhantomData })
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} else {
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None
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}
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}
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}
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impl Parse<SourceFile> {
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pub fn debug_dump(&self) -> String {
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let mut buf = format!("{:#?}", self.tree().syntax());
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for err in self.errors.iter() {
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writeln!(buf, "error {:?}: {}", err.location(), err.kind()).unwrap();
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}
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buf
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}
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pub fn reparse(&self, edit: &AtomTextEdit) -> Parse<SourceFile> {
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self.incremental_reparse(edit).unwrap_or_else(|| self.full_reparse(edit))
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}
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fn incremental_reparse(&self, edit: &AtomTextEdit) -> Option<Parse<SourceFile>> {
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// FIXME: validation errors are not handled here
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parsing::incremental_reparse(self.tree().syntax(), edit, self.errors.to_vec()).map(
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|(green_node, errors, _reparsed_range)| Parse {
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green: green_node,
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errors: Arc::new(errors),
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_ty: PhantomData,
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},
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)
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}
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fn full_reparse(&self, edit: &AtomTextEdit) -> Parse<SourceFile> {
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let text = edit.apply(self.tree().syntax().text().to_string());
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SourceFile::parse(&text)
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}
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}
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/// `SourceFile` represents a parse tree for a single Rust file.
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pub use crate::ast::SourceFile;
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impl SourceFile {
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pub fn parse(text: &str) -> Parse<SourceFile> {
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let (green, mut errors) = parsing::parse_text(text);
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let root = SyntaxNode::new_root(green.clone());
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if cfg!(debug_assertions) {
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validation::validate_block_structure(&root);
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}
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errors.extend(validation::validate(&root));
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assert_eq!(root.kind(), SyntaxKind::SOURCE_FILE);
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Parse { green, errors: Arc::new(errors), _ty: PhantomData }
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}
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}
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/// This test does not assert anything and instead just shows off the crate's
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/// API.
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#[test]
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fn api_walkthrough() {
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use ast::{ModuleItemOwner, NameOwner};
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let source_code = "
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fn foo() {
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1 + 1
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}
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";
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// `SourceFile` is the main entry point.
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//
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// The `parse` method returns a `Parse` -- a pair of syntax tree and a list
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// of errors. That is, syntax tree is constructed even in presence of errors.
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let parse = SourceFile::parse(source_code);
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assert!(parse.errors().is_empty());
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// The `tree` method returns an owned syntax node of type `SourceFile`.
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// Owned nodes are cheap: inside, they are `Rc` handles to the underling data.
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let file: SourceFile = parse.tree();
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// `SourceFile` is the root of the syntax tree. We can iterate file's items.
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// Let's fetch the `foo` function.
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let mut func = None;
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for item in file.items() {
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match item {
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ast::ModuleItem::FnDef(f) => func = Some(f),
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_ => unreachable!(),
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}
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}
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let func: ast::FnDef = func.unwrap();
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// Each AST node has a bunch of getters for children. All getters return
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// `Option`s though, to account for incomplete code. Some getters are common
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// for several kinds of node. In this case, a trait like `ast::NameOwner`
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// usually exists. By convention, all ast types should be used with `ast::`
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// qualifier.
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let name: Option<ast::Name> = func.name();
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let name = name.unwrap();
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assert_eq!(name.text(), "foo");
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// Let's get the `1 + 1` expression!
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let block: ast::Block = func.body().unwrap();
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let expr: ast::Expr = block.expr().unwrap();
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// Enums are used to group related ast nodes together, and can be used for
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// matching. However, because there are no public fields, it's possible to
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// match only the top level enum: that is the price we pay for increased API
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// flexibility
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let bin_expr: &ast::BinExpr = match &expr {
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ast::Expr::BinExpr(e) => e,
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_ => unreachable!(),
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};
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// Besides the "typed" AST API, there's an untyped CST one as well.
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// To switch from AST to CST, call `.syntax()` method:
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let expr_syntax: &SyntaxNode = expr.syntax();
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// Note how `expr` and `bin_expr` are in fact the same node underneath:
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assert!(expr_syntax == bin_expr.syntax());
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// To go from CST to AST, `AstNode::cast` function is used:
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let _expr: ast::Expr = match ast::Expr::cast(expr_syntax.clone()) {
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Some(e) => e,
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None => unreachable!(),
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};
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// The two properties each syntax node has is a `SyntaxKind`:
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assert_eq!(expr_syntax.kind(), SyntaxKind::BIN_EXPR);
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// And text range:
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assert_eq!(expr_syntax.text_range(), TextRange::from_to(32.into(), 37.into()));
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// You can get node's text as a `SyntaxText` object, which will traverse the
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// tree collecting token's text:
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let text: SyntaxText = expr_syntax.text();
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assert_eq!(text.to_string(), "1 + 1");
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// There's a bunch of traversal methods on `SyntaxNode`:
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assert_eq!(expr_syntax.parent().as_ref(), Some(block.syntax()));
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assert_eq!(block.syntax().first_child_or_token().map(|it| it.kind()), Some(T!['{']));
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assert_eq!(
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expr_syntax.next_sibling_or_token().map(|it| it.kind()),
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Some(SyntaxKind::WHITESPACE)
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);
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// As well as some iterator helpers:
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let f = expr_syntax.ancestors().find_map(ast::FnDef::cast);
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assert_eq!(f, Some(func));
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assert!(expr_syntax.siblings_with_tokens(Direction::Next).any(|it| it.kind() == T!['}']));
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assert_eq!(
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expr_syntax.descendants_with_tokens().count(),
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8, // 5 tokens `1`, ` `, `+`, ` `, `!`
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// 2 child literal expressions: `1`, `1`
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// 1 the node itself: `1 + 1`
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);
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// There's also a `preorder` method with a more fine-grained iteration control:
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let mut buf = String::new();
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let mut indent = 0;
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for event in expr_syntax.preorder_with_tokens() {
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match event {
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WalkEvent::Enter(node) => {
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let text = match &node {
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NodeOrToken::Node(it) => it.text().to_string(),
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NodeOrToken::Token(it) => it.text().to_string(),
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};
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buf += &format!("{:indent$}{:?} {:?}\n", " ", text, node.kind(), indent = indent);
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indent += 2;
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}
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WalkEvent::Leave(_) => indent -= 2,
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}
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}
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assert_eq!(indent, 0);
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assert_eq!(
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buf.trim(),
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r#"
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"1 + 1" BIN_EXPR
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"1" LITERAL
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"1" INT_NUMBER
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" " WHITESPACE
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"+" PLUS
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" " WHITESPACE
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"1" LITERAL
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"1" INT_NUMBER
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"#
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.trim()
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);
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// To recursively process the tree, there are three approaches:
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// 1. explicitly call getter methods on AST nodes.
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// 2. use descendants and `AstNode::cast`.
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// 3. use descendants and the visitor.
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//
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// Here's how the first one looks like:
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let exprs_cast: Vec<String> = file
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.syntax()
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.descendants()
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.filter_map(ast::Expr::cast)
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.map(|expr| expr.syntax().text().to_string())
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.collect();
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// An alternative is to use a visitor. The visitor does not do traversal
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// automatically (so it's more akin to a generic lambda) and is constructed
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// from closures. This seems more flexible than a single generated visitor
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// trait.
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use algo::visit::{visitor, Visitor};
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let mut exprs_visit = Vec::new();
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for node in file.syntax().descendants() {
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if let Some(result) =
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visitor().visit::<ast::Expr, _>(|expr| expr.syntax().text().to_string()).accept(&node)
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{
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exprs_visit.push(result);
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}
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}
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assert_eq!(exprs_cast, exprs_visit);
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}
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