ide_ssr/
nester.rs

1//! Converts a flat collection of matches into a nested form suitable for replacement. When there
2//! are multiple matches for a node, or that overlap, priority is given to the earlier rule. Nested
3//! matches are only permitted if the inner match is contained entirely within a placeholder of an
4//! outer match.
5//!
6//! For example, if our search pattern is `foo(foo($a))` and the code had `foo(foo(foo(foo(42))))`,
7//! then we'll get 3 matches, however only the outermost and innermost matches can be accepted. The
8//! middle match would take the second `foo` from the outer match.
9
10use ide_db::FxHashMap;
11use syntax::SyntaxNode;
12
13use crate::{Match, SsrMatches};
14
15pub(crate) fn nest_and_remove_collisions(
16    mut matches: Vec<Match>,
17    sema: &hir::Semantics<'_, ide_db::RootDatabase>,
18) -> SsrMatches {
19    // We sort the matches by depth then by rule index. Sorting by depth means that by the time we
20    // see a match, any parent matches or conflicting matches will have already been seen. Sorting
21    // by rule_index means that if there are two matches for the same node, the rule added first
22    // will take precedence.
23    matches.sort_by(|a, b| a.depth.cmp(&b.depth).then_with(|| a.rule_index.cmp(&b.rule_index)));
24    let mut collector = MatchCollector::default();
25    for m in matches {
26        collector.add_match(m, sema);
27    }
28    collector.into()
29}
30
31#[derive(Default)]
32struct MatchCollector {
33    matches_by_node: FxHashMap<SyntaxNode, Match>,
34}
35
36impl MatchCollector {
37    /// Attempts to add `m` to matches. If it conflicts with an existing match, it is discarded. If
38    /// it is entirely within the a placeholder of an existing match, then it is added as a child
39    /// match of the existing match.
40    fn add_match(&mut self, m: Match, sema: &hir::Semantics<'_, ide_db::RootDatabase>) {
41        let matched_node = m.matched_node.clone();
42        if let Some(existing) = self.matches_by_node.get_mut(&matched_node) {
43            try_add_sub_match(m, existing, sema);
44            return;
45        }
46        for ancestor in sema.ancestors_with_macros(m.matched_node.clone()) {
47            if let Some(existing) = self.matches_by_node.get_mut(&ancestor) {
48                try_add_sub_match(m, existing, sema);
49                return;
50            }
51        }
52        self.matches_by_node.insert(matched_node, m);
53    }
54}
55
56/// Attempts to add `m` as a sub-match of `existing`.
57fn try_add_sub_match(
58    m: Match,
59    existing: &mut Match,
60    sema: &hir::Semantics<'_, ide_db::RootDatabase>,
61) {
62    for p in existing.placeholder_values.values_mut() {
63        // Note, no need to check if p.range.file is equal to m.range.file, since we
64        // already know we're within `existing`.
65        if p.range.range.contains_range(m.range.range) {
66            // Convert the inner matches in `p` into a temporary MatchCollector. When
67            // we're done, we then convert it back into an SsrMatches. If we expected
68            // lots of inner matches, it might be worthwhile keeping a MatchCollector
69            // around for each placeholder match. However we expect most placeholder
70            // will have 0 and a few will have 1. More than that should hopefully be
71            // exceptional.
72            let mut collector = MatchCollector::default();
73            for m in std::mem::take(&mut p.inner_matches.matches) {
74                collector.matches_by_node.insert(m.matched_node.clone(), m);
75            }
76            collector.add_match(m, sema);
77            p.inner_matches = collector.into();
78            break;
79        }
80    }
81}
82
83impl From<MatchCollector> for SsrMatches {
84    fn from(mut match_collector: MatchCollector) -> Self {
85        let mut matches = SsrMatches::default();
86        for (_, m) in match_collector.matches_by_node.drain() {
87            matches.matches.push(m);
88        }
89        matches.matches.sort_by(|a, b| {
90            // Order matches by file_id then by start range. This should be sufficient since ranges
91            // shouldn't be overlapping.
92            a.range
93                .file_id
94                .cmp(&b.range.file_id)
95                .then_with(|| a.range.range.start().cmp(&b.range.range.start()))
96        });
97        matches
98    }
99}
ide_ssr/nester.rs

ide_ssr/
nester.rs
