rust/crates/ra_ssr/src/matching.rs

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//! This module is responsible for matching a search pattern against a node in the AST. In the
//! process of matching, placeholder values are recorded.
use crate::{
parsing::{Placeholder, SsrTemplate},
SsrMatches, SsrPattern, SsrRule,
};
use hir::Semantics;
use ra_db::FileRange;
use ra_syntax::ast::{AstNode, AstToken};
use ra_syntax::{
ast, SyntaxElement, SyntaxElementChildren, SyntaxKind, SyntaxNode, SyntaxToken, TextRange,
};
use rustc_hash::FxHashMap;
use std::{cell::Cell, iter::Peekable};
// Creates a match error. If we're currently attempting to match some code that we thought we were
// going to match, as indicated by the --debug-snippet flag, then populate the reason field.
macro_rules! match_error {
($e:expr) => {{
MatchFailed {
reason: if recording_match_fail_reasons() {
Some(format!("{}", $e))
} else {
None
}
}
}};
($fmt:expr, $($arg:tt)+) => {{
MatchFailed {
reason: if recording_match_fail_reasons() {
Some(format!($fmt, $($arg)+))
} else {
None
}
}
}};
}
// Fails the current match attempt, recording the supplied reason if we're recording match fail reasons.
macro_rules! fail_match {
($($args:tt)*) => {return Err(match_error!($($args)*))};
}
/// Information about a match that was found.
#[derive(Debug)]
pub(crate) struct Match {
pub(crate) range: TextRange,
pub(crate) matched_node: SyntaxNode,
pub(crate) placeholder_values: FxHashMap<Var, PlaceholderMatch>,
pub(crate) ignored_comments: Vec<ast::Comment>,
// A copy of the template for the rule that produced this match. We store this on the match for
// if/when we do replacement.
pub(crate) template: SsrTemplate,
}
/// Represents a `$var` in an SSR query.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub(crate) struct Var(pub String);
/// Information about a placeholder bound in a match.
#[derive(Debug)]
pub(crate) struct PlaceholderMatch {
/// The node that the placeholder matched to. If set, then we'll search for further matches
/// within this node. It isn't set when we match tokens within a macro call's token tree.
pub(crate) node: Option<SyntaxNode>,
pub(crate) range: FileRange,
/// More matches, found within `node`.
pub(crate) inner_matches: SsrMatches,
}
#[derive(Debug)]
pub(crate) struct MatchFailureReason {
pub(crate) reason: String,
}
/// An "error" indicating that matching failed. Use the fail_match! macro to create and return this.
#[derive(Clone)]
pub(crate) struct MatchFailed {
/// The reason why we failed to match. Only present when debug_active true in call to
/// `get_match`.
pub(crate) reason: Option<String>,
}
/// Checks if `code` matches the search pattern found in `search_scope`, returning information about
/// the match, if it does. Since we only do matching in this module and searching is done by the
/// parent module, we don't populate nested matches.
pub(crate) fn get_match(
debug_active: bool,
rule: &SsrRule,
code: &SyntaxNode,
restrict_range: &Option<FileRange>,
sema: &Semantics<ra_ide_db::RootDatabase>,
) -> Result<Match, MatchFailed> {
record_match_fails_reasons_scope(debug_active, || {
MatchState::try_match(rule, code, restrict_range, sema)
})
}
/// Inputs to matching. This cannot be part of `MatchState`, since we mutate `MatchState` and in at
/// least one case need to hold a borrow of a placeholder from the input pattern while calling a
/// mutable `MatchState` method.
struct MatchInputs<'pattern> {
ssr_pattern: &'pattern SsrPattern,
}
/// State used while attempting to match our search pattern against a particular node of the AST.
struct MatchState<'db, 'sema> {
sema: &'sema Semantics<'db, ra_ide_db::RootDatabase>,
/// If any placeholders come from anywhere outside of this range, then the match will be
/// rejected.
restrict_range: Option<FileRange>,
/// The match that we're building. We do two passes for a successful match. On the first pass,
/// this is None so that we can avoid doing things like storing copies of what placeholders
/// matched to. If that pass succeeds, then we do a second pass where we collect those details.
/// This means that if we have a pattern like `$a.foo()` we won't do an insert into the
/// placeholders map for every single method call in the codebase. Instead we'll discard all the
/// method calls that aren't calls to `foo` on the first pass and only insert into the
/// placeholders map on the second pass. Likewise for ignored comments.
match_out: Option<Match>,
}
impl<'db, 'sema> MatchState<'db, 'sema> {
fn try_match(
rule: &SsrRule,
code: &SyntaxNode,
restrict_range: &Option<FileRange>,
sema: &'sema Semantics<'db, ra_ide_db::RootDatabase>,
) -> Result<Match, MatchFailed> {
let mut match_state =
MatchState { sema, restrict_range: restrict_range.clone(), match_out: None };
let match_inputs = MatchInputs { ssr_pattern: &rule.pattern };
let pattern_tree = rule.pattern.tree_for_kind(code.kind())?;
// First pass at matching, where we check that node types and idents match.
match_state.attempt_match_node(&match_inputs, &pattern_tree, code)?;
match_state.validate_range(&sema.original_range(code))?;
match_state.match_out = Some(Match {
range: sema.original_range(code).range,
matched_node: code.clone(),
placeholder_values: FxHashMap::default(),
ignored_comments: Vec::new(),
template: rule.template.clone(),
});
// Second matching pass, where we record placeholder matches, ignored comments and maybe do
// any other more expensive checks that we didn't want to do on the first pass.
match_state.attempt_match_node(&match_inputs, &pattern_tree, code)?;
Ok(match_state.match_out.unwrap())
}
/// Checks that `range` is within the permitted range if any. This is applicable when we're
/// processing a macro expansion and we want to fail the match if we're working with a node that
/// didn't originate from the token tree of the macro call.
fn validate_range(&self, range: &FileRange) -> Result<(), MatchFailed> {
if let Some(restrict_range) = &self.restrict_range {
if restrict_range.file_id != range.file_id
|| !restrict_range.range.contains_range(range.range)
{
fail_match!("Node originated from a macro");
}
}
Ok(())
}
fn attempt_match_node(
&mut self,
match_inputs: &MatchInputs,
pattern: &SyntaxNode,
code: &SyntaxNode,
) -> Result<(), MatchFailed> {
// Handle placeholders.
if let Some(placeholder) =
match_inputs.get_placeholder(&SyntaxElement::Node(pattern.clone()))
{
if self.match_out.is_none() {
return Ok(());
}
let original_range = self.sema.original_range(code);
// We validated the range for the node when we started the match, so the placeholder
// probably can't fail range validation, but just to be safe...
self.validate_range(&original_range)?;
if let Some(match_out) = &mut self.match_out {
match_out.placeholder_values.insert(
Var(placeholder.ident.to_string()),
PlaceholderMatch::new(code, original_range),
);
}
return Ok(());
}
// Non-placeholders.
if pattern.kind() != code.kind() {
fail_match!("Pattern had a {:?}, code had {:?}", pattern.kind(), code.kind());
}
// Some kinds of nodes have special handling. For everything else, we fall back to default
// matching.
match code.kind() {
SyntaxKind::RECORD_FIELD_LIST => {
self.attempt_match_record_field_list(match_inputs, pattern, code)
}
SyntaxKind::TOKEN_TREE => self.attempt_match_token_tree(match_inputs, pattern, code),
_ => self.attempt_match_node_children(match_inputs, pattern, code),
}
}
fn attempt_match_node_children(
&mut self,
match_inputs: &MatchInputs,
pattern: &SyntaxNode,
code: &SyntaxNode,
) -> Result<(), MatchFailed> {
self.attempt_match_sequences(
match_inputs,
PatternIterator::new(pattern),
code.children_with_tokens(),
)
}
fn attempt_match_sequences(
&mut self,
match_inputs: &MatchInputs,
pattern_it: PatternIterator,
mut code_it: SyntaxElementChildren,
) -> Result<(), MatchFailed> {
let mut pattern_it = pattern_it.peekable();
loop {
match self.next_non_trivial(&mut code_it) {
None => {
if let Some(p) = pattern_it.next() {
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fail_match!("Part of the pattern was unmatched: {:?}", p);
}
return Ok(());
}
Some(SyntaxElement::Token(c)) => {
self.attempt_match_token(&mut pattern_it, &c)?;
}
Some(SyntaxElement::Node(c)) => match pattern_it.next() {
Some(SyntaxElement::Node(p)) => {
self.attempt_match_node(match_inputs, &p, &c)?;
}
Some(p) => fail_match!("Pattern wanted '{}', code has {}", p, c.text()),
None => fail_match!("Pattern reached end, code has {}", c.text()),
},
}
}
}
fn attempt_match_token(
&mut self,
pattern: &mut Peekable<PatternIterator>,
code: &ra_syntax::SyntaxToken,
) -> Result<(), MatchFailed> {
self.record_ignored_comments(code);
// Ignore whitespace and comments.
if code.kind().is_trivia() {
return Ok(());
}
if let Some(SyntaxElement::Token(p)) = pattern.peek() {
// If the code has a comma and the pattern is about to close something, then accept the
// comma without advancing the pattern. i.e. ignore trailing commas.
if code.kind() == SyntaxKind::COMMA && is_closing_token(p.kind()) {
return Ok(());
}
// Conversely, if the pattern has a comma and the code doesn't, skip that part of the
// pattern and continue to match the code.
if p.kind() == SyntaxKind::COMMA && is_closing_token(code.kind()) {
pattern.next();
}
}
// Consume an element from the pattern and make sure it matches.
match pattern.next() {
Some(SyntaxElement::Token(p)) => {
if p.kind() != code.kind() || p.text() != code.text() {
fail_match!(
"Pattern wanted token '{}' ({:?}), but code had token '{}' ({:?})",
p.text(),
p.kind(),
code.text(),
code.kind()
)
}
}
Some(SyntaxElement::Node(p)) => {
// Not sure if this is actually reachable.
fail_match!(
"Pattern wanted {:?}, but code had token '{}' ({:?})",
p,
code.text(),
code.kind()
);
}
None => {
fail_match!("Pattern exhausted, while code remains: `{}`", code.text());
}
}
Ok(())
}
/// We want to allow the records to match in any order, so we have special matching logic for
/// them.
fn attempt_match_record_field_list(
&mut self,
match_inputs: &MatchInputs,
pattern: &SyntaxNode,
code: &SyntaxNode,
) -> Result<(), MatchFailed> {
// Build a map keyed by field name.
let mut fields_by_name = FxHashMap::default();
for child in code.children() {
if let Some(record) = ast::RecordField::cast(child.clone()) {
if let Some(name) = record.field_name() {
fields_by_name.insert(name.text().clone(), child.clone());
}
}
}
for p in pattern.children_with_tokens() {
if let SyntaxElement::Node(p) = p {
if let Some(name_element) = p.first_child_or_token() {
if match_inputs.get_placeholder(&name_element).is_some() {
// If the pattern is using placeholders for field names then order
// independence doesn't make sense. Fall back to regular ordered
// matching.
return self.attempt_match_node_children(match_inputs, pattern, code);
}
if let Some(ident) = only_ident(name_element) {
let code_record = fields_by_name.remove(ident.text()).ok_or_else(|| {
match_error!(
"Placeholder has record field '{}', but code doesn't",
ident
)
})?;
self.attempt_match_node(match_inputs, &p, &code_record)?;
}
}
}
}
if let Some(unmatched_fields) = fields_by_name.keys().next() {
fail_match!(
"{} field(s) of a record literal failed to match, starting with {}",
fields_by_name.len(),
unmatched_fields
);
}
Ok(())
}
/// Outside of token trees, a placeholder can only match a single AST node, whereas in a token
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/// tree it can match a sequence of tokens. Note, that this code will only be used when the
/// pattern matches the macro invocation. For matches within the macro call, we'll already have
/// expanded the macro.
fn attempt_match_token_tree(
&mut self,
match_inputs: &MatchInputs,
pattern: &SyntaxNode,
code: &ra_syntax::SyntaxNode,
) -> Result<(), MatchFailed> {
let mut pattern = PatternIterator::new(pattern).peekable();
let mut children = code.children_with_tokens();
while let Some(child) = children.next() {
if let Some(placeholder) = pattern.peek().and_then(|p| match_inputs.get_placeholder(p))
{
pattern.next();
let next_pattern_token = pattern
.peek()
.and_then(|p| match p {
SyntaxElement::Token(t) => Some(t.clone()),
SyntaxElement::Node(n) => n.first_token(),
})
.map(|p| p.text().to_string());
let first_matched_token = child.clone();
let mut last_matched_token = child;
// Read code tokens util we reach one equal to the next token from our pattern
// or we reach the end of the token tree.
while let Some(next) = children.next() {
match &next {
SyntaxElement::Token(t) => {
if Some(t.to_string()) == next_pattern_token {
pattern.next();
break;
}
}
SyntaxElement::Node(n) => {
if let Some(first_token) = n.first_token() {
if Some(first_token.to_string()) == next_pattern_token {
if let Some(SyntaxElement::Node(p)) = pattern.next() {
// We have a subtree that starts with the next token in our pattern.
self.attempt_match_token_tree(match_inputs, &p, &n)?;
break;
}
}
}
}
};
last_matched_token = next;
}
if let Some(match_out) = &mut self.match_out {
match_out.placeholder_values.insert(
Var(placeholder.ident.to_string()),
PlaceholderMatch::from_range(FileRange {
file_id: self.sema.original_range(code).file_id,
range: first_matched_token
.text_range()
.cover(last_matched_token.text_range()),
}),
);
}
continue;
}
// Match literal (non-placeholder) tokens.
match child {
SyntaxElement::Token(token) => {
self.attempt_match_token(&mut pattern, &token)?;
}
SyntaxElement::Node(node) => match pattern.next() {
Some(SyntaxElement::Node(p)) => {
self.attempt_match_token_tree(match_inputs, &p, &node)?;
}
Some(SyntaxElement::Token(p)) => fail_match!(
"Pattern has token '{}', code has subtree '{}'",
p.text(),
node.text()
),
None => fail_match!("Pattern has nothing, code has '{}'", node.text()),
},
}
}
if let Some(p) = pattern.next() {
fail_match!("Reached end of token tree in code, but pattern still has {:?}", p);
}
Ok(())
}
fn next_non_trivial(&mut self, code_it: &mut SyntaxElementChildren) -> Option<SyntaxElement> {
loop {
let c = code_it.next();
if let Some(SyntaxElement::Token(t)) = &c {
self.record_ignored_comments(t);
if t.kind().is_trivia() {
continue;
}
}
return c;
}
}
fn record_ignored_comments(&mut self, token: &SyntaxToken) {
if token.kind() == SyntaxKind::COMMENT {
if let Some(match_out) = &mut self.match_out {
if let Some(comment) = ast::Comment::cast(token.clone()) {
match_out.ignored_comments.push(comment);
}
}
}
}
}
impl MatchInputs<'_> {
fn get_placeholder(&self, element: &SyntaxElement) -> Option<&Placeholder> {
only_ident(element.clone())
.and_then(|ident| self.ssr_pattern.placeholders_by_stand_in.get(ident.text()))
}
}
fn is_closing_token(kind: SyntaxKind) -> bool {
kind == SyntaxKind::R_PAREN || kind == SyntaxKind::R_CURLY || kind == SyntaxKind::R_BRACK
}
pub(crate) fn record_match_fails_reasons_scope<F, T>(debug_active: bool, f: F) -> T
where
F: Fn() -> T,
{
RECORDING_MATCH_FAIL_REASONS.with(|c| c.set(debug_active));
let res = f();
RECORDING_MATCH_FAIL_REASONS.with(|c| c.set(false));
res
}
// For performance reasons, we don't want to record the reason why every match fails, only the bit
// of code that the user indicated they thought would match. We use a thread local to indicate when
// we are trying to match that bit of code. This saves us having to pass a boolean into all the bits
// of code that can make the decision to not match.
thread_local! {
pub static RECORDING_MATCH_FAIL_REASONS: Cell<bool> = Cell::new(false);
}
fn recording_match_fail_reasons() -> bool {
RECORDING_MATCH_FAIL_REASONS.with(|c| c.get())
}
impl PlaceholderMatch {
fn new(node: &SyntaxNode, range: FileRange) -> Self {
Self { node: Some(node.clone()), range, inner_matches: SsrMatches::default() }
}
fn from_range(range: FileRange) -> Self {
Self { node: None, range, inner_matches: SsrMatches::default() }
}
}
impl SsrPattern {
pub(crate) fn tree_for_kind(&self, kind: SyntaxKind) -> Result<&SyntaxNode, MatchFailed> {
let (tree, kind_name) = if ast::Expr::can_cast(kind) {
(&self.expr, "expression")
} else if ast::TypeRef::can_cast(kind) {
(&self.type_ref, "type reference")
} else if ast::ModuleItem::can_cast(kind) {
(&self.item, "item")
} else if ast::Path::can_cast(kind) {
(&self.path, "path")
} else if ast::Pat::can_cast(kind) {
(&self.pattern, "pattern")
} else {
fail_match!("Matching nodes of kind {:?} is not supported", kind);
};
match tree {
Some(tree) => Ok(tree),
None => fail_match!("Pattern cannot be parsed as a {}", kind_name),
}
}
}
// If `node` contains nothing but an ident then return it, otherwise return None.
fn only_ident(element: SyntaxElement) -> Option<SyntaxToken> {
match element {
SyntaxElement::Token(t) => {
if t.kind() == SyntaxKind::IDENT {
return Some(t);
}
}
SyntaxElement::Node(n) => {
let mut children = n.children_with_tokens();
if let (Some(only_child), None) = (children.next(), children.next()) {
return only_ident(only_child);
}
}
}
None
}
struct PatternIterator {
iter: SyntaxElementChildren,
}
impl Iterator for PatternIterator {
type Item = SyntaxElement;
fn next(&mut self) -> Option<SyntaxElement> {
while let Some(element) = self.iter.next() {
if !element.kind().is_trivia() {
return Some(element);
}
}
None
}
}
impl PatternIterator {
fn new(parent: &SyntaxNode) -> Self {
Self { iter: parent.children_with_tokens() }
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::MatchFinder;
#[test]
fn parse_match_replace() {
let rule: SsrRule = "foo($x) ==>> bar($x)".parse().unwrap();
let input = "fn main() { foo(1+2); }";
use ra_db::fixture::WithFixture;
let (db, file_id) = ra_ide_db::RootDatabase::with_single_file(input);
let mut match_finder = MatchFinder::new(&db);
match_finder.add_rule(rule);
let matches = match_finder.find_matches_in_file(file_id);
assert_eq!(matches.matches.len(), 1);
assert_eq!(matches.matches[0].matched_node.text(), "foo(1+2)");
assert_eq!(matches.matches[0].placeholder_values.len(), 1);
assert_eq!(
matches.matches[0].placeholder_values[&Var("x".to_string())]
.node
.as_ref()
.unwrap()
.text(),
"1+2"
);
let edit = crate::replacing::matches_to_edit(&matches, input);
let mut after = input.to_string();
edit.apply(&mut after);
assert_eq!(after, "fn main() { bar(1+2); }");
}
}