rust/crates/ide_ssr/src/parsing.rs
2021-12-28 17:00:55 +03:00

407 lines
14 KiB
Rust

//! This file contains code for parsing SSR rules, which look something like `foo($a) ==>> bar($b)`.
//! We first split everything before and after the separator `==>>`. Next, both the search pattern
//! and the replacement template get tokenized by the Rust tokenizer. Tokens are then searched for
//! placeholders, which start with `$`. For replacement templates, this is the final form. For
//! search patterns, we go further and parse the pattern as each kind of thing that we can match.
//! e.g. expressions, type references etc.
use rustc_hash::{FxHashMap, FxHashSet};
use std::{fmt::Display, str::FromStr};
use syntax::{SmolStr, SyntaxKind, SyntaxNode, T};
use crate::errors::bail;
use crate::{fragments, SsrError, SsrPattern, SsrRule};
#[derive(Debug)]
pub(crate) struct ParsedRule {
pub(crate) placeholders_by_stand_in: FxHashMap<SmolStr, Placeholder>,
pub(crate) pattern: SyntaxNode,
pub(crate) template: Option<SyntaxNode>,
}
#[derive(Debug)]
pub(crate) struct RawPattern {
tokens: Vec<PatternElement>,
}
// Part of a search or replace pattern.
#[derive(Clone, Debug, PartialEq, Eq)]
pub(crate) enum PatternElement {
Token(Token),
Placeholder(Placeholder),
}
#[derive(Clone, Debug, PartialEq, Eq)]
pub(crate) struct Placeholder {
/// The name of this placeholder. e.g. for "$a", this would be "a"
pub(crate) ident: Var,
/// A unique name used in place of this placeholder when we parse the pattern as Rust code.
stand_in_name: String,
pub(crate) constraints: Vec<Constraint>,
}
/// Represents a `$var` in an SSR query.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub(crate) struct Var(pub(crate) String);
#[derive(Clone, Debug, PartialEq, Eq)]
pub(crate) enum Constraint {
Kind(NodeKind),
Not(Box<Constraint>),
}
#[derive(Clone, Debug, PartialEq, Eq)]
pub(crate) enum NodeKind {
Literal,
}
#[derive(Debug, Clone, PartialEq, Eq)]
pub(crate) struct Token {
kind: SyntaxKind,
pub(crate) text: SmolStr,
}
impl ParsedRule {
fn new(
pattern: &RawPattern,
template: Option<&RawPattern>,
) -> Result<Vec<ParsedRule>, SsrError> {
let raw_pattern = pattern.as_rust_code();
let raw_template = template.map(|t| t.as_rust_code());
let raw_template = raw_template.as_deref();
let mut builder = RuleBuilder {
placeholders_by_stand_in: pattern.placeholders_by_stand_in(),
rules: Vec::new(),
};
let raw_template_stmt = raw_template.map(fragments::stmt);
if let raw_template_expr @ Some(Ok(_)) = raw_template.map(fragments::expr) {
builder.try_add(fragments::expr(&raw_pattern), raw_template_expr);
} else {
builder.try_add(fragments::expr(&raw_pattern), raw_template_stmt.clone());
}
builder.try_add(fragments::ty(&raw_pattern), raw_template.map(fragments::ty));
builder.try_add(fragments::item(&raw_pattern), raw_template.map(fragments::item));
builder.try_add(fragments::pat(&raw_pattern), raw_template.map(fragments::pat));
builder.try_add(fragments::stmt(&raw_pattern), raw_template_stmt);
builder.build()
}
}
struct RuleBuilder {
placeholders_by_stand_in: FxHashMap<SmolStr, Placeholder>,
rules: Vec<ParsedRule>,
}
impl RuleBuilder {
fn try_add(
&mut self,
pattern: Result<SyntaxNode, ()>,
template: Option<Result<SyntaxNode, ()>>,
) {
match (pattern, template) {
(Ok(pattern), Some(Ok(template))) => self.rules.push(ParsedRule {
placeholders_by_stand_in: self.placeholders_by_stand_in.clone(),
pattern,
template: Some(template),
}),
(Ok(pattern), None) => self.rules.push(ParsedRule {
placeholders_by_stand_in: self.placeholders_by_stand_in.clone(),
pattern,
template: None,
}),
_ => {}
}
}
fn build(mut self) -> Result<Vec<ParsedRule>, SsrError> {
if self.rules.is_empty() {
bail!("Not a valid Rust expression, type, item, path or pattern");
}
// If any rules contain paths, then we reject any rules that don't contain paths. Allowing a
// mix leads to strange semantics, since the path-based rules only match things where the
// path refers to semantically the same thing, whereas the non-path-based rules could match
// anything. Specifically, if we have a rule like `foo ==>> bar` we only want to match the
// `foo` that is in the current scope, not any `foo`. However "foo" can be parsed as a
// pattern (IDENT_PAT -> NAME -> IDENT). Allowing such a rule through would result in
// renaming everything called `foo` to `bar`. It'd also be slow, since without a path, we'd
// have to use the slow-scan search mechanism.
if self.rules.iter().any(|rule| contains_path(&rule.pattern)) {
let old_len = self.rules.len();
self.rules.retain(|rule| contains_path(&rule.pattern));
if self.rules.len() < old_len {
cov_mark::hit!(pattern_is_a_single_segment_path);
}
}
Ok(self.rules)
}
}
/// Returns whether there are any paths in `node`.
fn contains_path(node: &SyntaxNode) -> bool {
node.kind() == SyntaxKind::PATH
|| node.descendants().any(|node| node.kind() == SyntaxKind::PATH)
}
impl FromStr for SsrRule {
type Err = SsrError;
fn from_str(query: &str) -> Result<SsrRule, SsrError> {
let mut it = query.split("==>>");
let pattern = it.next().expect("at least empty string").trim();
let template = it
.next()
.ok_or_else(|| SsrError("Cannot find delimiter `==>>`".into()))?
.trim()
.to_string();
if it.next().is_some() {
return Err(SsrError("More than one delimiter found".into()));
}
let raw_pattern = pattern.parse()?;
let raw_template = template.parse()?;
let parsed_rules = ParsedRule::new(&raw_pattern, Some(&raw_template))?;
let rule = SsrRule { pattern: raw_pattern, template: raw_template, parsed_rules };
validate_rule(&rule)?;
Ok(rule)
}
}
impl FromStr for RawPattern {
type Err = SsrError;
fn from_str(pattern_str: &str) -> Result<RawPattern, SsrError> {
Ok(RawPattern { tokens: parse_pattern(pattern_str)? })
}
}
impl RawPattern {
/// Returns this search pattern as Rust source code that we can feed to the Rust parser.
fn as_rust_code(&self) -> String {
let mut res = String::new();
for t in &self.tokens {
res.push_str(match t {
PatternElement::Token(token) => token.text.as_str(),
PatternElement::Placeholder(placeholder) => placeholder.stand_in_name.as_str(),
});
}
res
}
pub(crate) fn placeholders_by_stand_in(&self) -> FxHashMap<SmolStr, Placeholder> {
let mut res = FxHashMap::default();
for t in &self.tokens {
if let PatternElement::Placeholder(placeholder) = t {
res.insert(SmolStr::new(placeholder.stand_in_name.clone()), placeholder.clone());
}
}
res
}
}
impl FromStr for SsrPattern {
type Err = SsrError;
fn from_str(pattern_str: &str) -> Result<SsrPattern, SsrError> {
let raw_pattern = pattern_str.parse()?;
let parsed_rules = ParsedRule::new(&raw_pattern, None)?;
Ok(SsrPattern { parsed_rules })
}
}
/// Returns `pattern_str`, parsed as a search or replace pattern. If `remove_whitespace` is true,
/// then any whitespace tokens will be removed, which we do for the search pattern, but not for the
/// replace pattern.
fn parse_pattern(pattern_str: &str) -> Result<Vec<PatternElement>, SsrError> {
let mut res = Vec::new();
let mut placeholder_names = FxHashSet::default();
let mut tokens = tokenize(pattern_str)?.into_iter();
while let Some(token) = tokens.next() {
if token.kind == T![$] {
let placeholder = parse_placeholder(&mut tokens)?;
if !placeholder_names.insert(placeholder.ident.clone()) {
bail!("Placeholder `{}` repeats more than once", placeholder.ident);
}
res.push(PatternElement::Placeholder(placeholder));
} else {
res.push(PatternElement::Token(token));
}
}
Ok(res)
}
/// Checks for errors in a rule. e.g. the replace pattern referencing placeholders that the search
/// pattern didn't define.
fn validate_rule(rule: &SsrRule) -> Result<(), SsrError> {
let mut defined_placeholders = FxHashSet::default();
for p in &rule.pattern.tokens {
if let PatternElement::Placeholder(placeholder) = p {
defined_placeholders.insert(&placeholder.ident);
}
}
let mut undefined = Vec::new();
for p in &rule.template.tokens {
if let PatternElement::Placeholder(placeholder) = p {
if !defined_placeholders.contains(&placeholder.ident) {
undefined.push(placeholder.ident.to_string());
}
if !placeholder.constraints.is_empty() {
bail!("Replacement placeholders cannot have constraints");
}
}
}
if !undefined.is_empty() {
bail!("Replacement contains undefined placeholders: {}", undefined.join(", "));
}
Ok(())
}
fn tokenize(source: &str) -> Result<Vec<Token>, SsrError> {
let lexed = parser::LexedStr::new(source);
if let Some((_, first_error)) = lexed.errors().next() {
bail!("Failed to parse pattern: {}", first_error);
}
let mut tokens: Vec<Token> = Vec::new();
for i in 0..lexed.len() {
tokens.push(Token { kind: lexed.kind(i), text: lexed.text(i).into() });
}
Ok(tokens)
}
fn parse_placeholder(tokens: &mut std::vec::IntoIter<Token>) -> Result<Placeholder, SsrError> {
let mut name = None;
let mut constraints = Vec::new();
if let Some(token) = tokens.next() {
match token.kind {
SyntaxKind::IDENT => {
name = Some(token.text);
}
T!['{'] => {
let token =
tokens.next().ok_or_else(|| SsrError::new("Unexpected end of placeholder"))?;
if token.kind == SyntaxKind::IDENT {
name = Some(token.text);
}
loop {
let token = tokens
.next()
.ok_or_else(|| SsrError::new("Placeholder is missing closing brace '}'"))?;
match token.kind {
T![:] => {
constraints.push(parse_constraint(tokens)?);
}
T!['}'] => break,
_ => bail!("Unexpected token while parsing placeholder: '{}'", token.text),
}
}
}
_ => {
bail!("Placeholders should either be $name or ${{name:constraints}}");
}
}
}
let name = name.ok_or_else(|| SsrError::new("Placeholder ($) with no name"))?;
Ok(Placeholder::new(name, constraints))
}
fn parse_constraint(tokens: &mut std::vec::IntoIter<Token>) -> Result<Constraint, SsrError> {
let constraint_type = tokens
.next()
.ok_or_else(|| SsrError::new("Found end of placeholder while looking for a constraint"))?
.text
.to_string();
match constraint_type.as_str() {
"kind" => {
expect_token(tokens, "(")?;
let t = tokens.next().ok_or_else(|| {
SsrError::new("Unexpected end of constraint while looking for kind")
})?;
if t.kind != SyntaxKind::IDENT {
bail!("Expected ident, found {:?} while parsing kind constraint", t.kind);
}
expect_token(tokens, ")")?;
Ok(Constraint::Kind(NodeKind::from(&t.text)?))
}
"not" => {
expect_token(tokens, "(")?;
let sub = parse_constraint(tokens)?;
expect_token(tokens, ")")?;
Ok(Constraint::Not(Box::new(sub)))
}
x => bail!("Unsupported constraint type '{}'", x),
}
}
fn expect_token(tokens: &mut std::vec::IntoIter<Token>, expected: &str) -> Result<(), SsrError> {
if let Some(t) = tokens.next() {
if t.text == expected {
return Ok(());
}
bail!("Expected {} found {}", expected, t.text);
}
bail!("Expected {} found end of stream", expected);
}
impl NodeKind {
fn from(name: &SmolStr) -> Result<NodeKind, SsrError> {
Ok(match name.as_str() {
"literal" => NodeKind::Literal,
_ => bail!("Unknown node kind '{}'", name),
})
}
}
impl Placeholder {
fn new(name: SmolStr, constraints: Vec<Constraint>) -> Self {
Self {
stand_in_name: format!("__placeholder_{}", name),
constraints,
ident: Var(name.to_string()),
}
}
}
impl Display for Var {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "${}", self.0)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn parser_happy_case() {
fn token(kind: SyntaxKind, text: &str) -> PatternElement {
PatternElement::Token(Token { kind, text: SmolStr::new(text) })
}
fn placeholder(name: &str) -> PatternElement {
PatternElement::Placeholder(Placeholder::new(SmolStr::new(name), Vec::new()))
}
let result: SsrRule = "foo($a, $b) ==>> bar($b, $a)".parse().unwrap();
assert_eq!(
result.pattern.tokens,
vec![
token(SyntaxKind::IDENT, "foo"),
token(T!['('], "("),
placeholder("a"),
token(T![,], ","),
token(SyntaxKind::WHITESPACE, " "),
placeholder("b"),
token(T![')'], ")"),
]
);
assert_eq!(
result.template.tokens,
vec![
token(SyntaxKind::IDENT, "bar"),
token(T!['('], "("),
placeholder("b"),
token(T![,], ","),
token(SyntaxKind::WHITESPACE, " "),
placeholder("a"),
token(T![')'], ")"),
]
);
}
}