1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
|
//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
import SwiftParser
import SwiftSyntax
/// Keeps track of SwiftSyntax trees for document snapshots and computes the
/// SwiftSyntax trees on demand.
actor SyntaxTreeManager {
/// A task that parses a SwiftSyntax tree from a source file, producing both
/// the syntax tree and the lookahead ranges that are needed for a subsequent
/// incremental parse.
private typealias SyntaxTreeComputation = Task<IncrementalParseResult, Never>
/// The tasks that compute syntax trees.
///
/// Conceptually, this is a dictionary. To prevent excessive memory usage we
/// only keep `cacheSize` entries within the array. Older entries are at the
/// end of the list, newer entries at the front.
private var syntaxTreeComputations:
[(
snapshotID: DocumentSnapshot.ID,
computation: SyntaxTreeComputation
)] = []
/// The number of syntax trees to keep.
///
/// - Note: This has been chosen without scientific measurements. The feeling
/// is that you rarely work on more than 5 files at once and 5 syntax trees
/// don't take up too much memory.
private let cacheSize = 5
/// - Important: For testing only
private var reusedNodeCallback: ReusedNodeCallback?
/// - Important: For testing only
func setReusedNodeCallback(_ callback: ReusedNodeCallback?) {
self.reusedNodeCallback = callback
}
/// The task that computes the syntax tree for the given document snapshot.
private func computation(for snapshotID: DocumentSnapshot.ID) -> SyntaxTreeComputation? {
return syntaxTreeComputations.first(where: { $0.snapshotID == snapshotID })?.computation
}
/// Set the task that computes the syntax tree for the given document snapshot.
///
/// If we are already storing `cacheSize` many syntax trees, the oldest one
/// will get discarded.
private func setComputation(for snapshotID: DocumentSnapshot.ID, computation: SyntaxTreeComputation) {
syntaxTreeComputations.insert((snapshotID, computation), at: 0)
// Remove any syntax trees for old versions of this document.
syntaxTreeComputations.removeAll(where: { $0.snapshotID < snapshotID })
// If we still have more than `cacheSize` syntax trees, delete the ones that
// were produced last. We can always re-compute them on-demand.
while syntaxTreeComputations.count > cacheSize {
syntaxTreeComputations.removeLast()
}
}
/// Get the SwiftSyntax tree for the given document snapshot.
func syntaxTree(for snapshot: DocumentSnapshot) async -> SourceFileSyntax {
return await incrementalParseResult(for: snapshot).tree
}
/// Get the `IncrementalParseResult` for the given document snapshot.
func incrementalParseResult(for snapshot: DocumentSnapshot) async -> IncrementalParseResult {
if let syntaxTreeComputation = computation(for: snapshot.id) {
return await syntaxTreeComputation.value
}
let task = Task {
return Parser.parseIncrementally(source: snapshot.text, parseTransition: nil)
}
setComputation(for: snapshot.id, computation: task)
return await task.value
}
/// Register that we have made an edit to an old document snapshot.
///
/// If we computed a syntax tree for the pre-edit snapshot, we will perform an
/// incremental parse to compute the syntax tree for the post-edit snapshot.
func registerEdit(preEditSnapshot: DocumentSnapshot, postEditSnapshot: DocumentSnapshot, edits: ConcurrentEdits) {
guard let preEditTreeComputation = computation(for: preEditSnapshot.id) else {
// We don't have the old tree and thus can't perform an incremental parse.
// So there's nothing to do. We will perform a full parse once we request
// the syntax tree for the first time.
return
}
let incrementalParseComputation = Task {
// Note: It could be the case that the pre-edit tree has not been fully
// computed yet when we enter this task and we will need to wait for its
// computation to finish. That is desired because the with very high
// likelihood it's faster to wait for the pre-edit parse to finish and
// perform an incremental parse (which should be very fast) than to start
// a new, full, from-scratch parse.
let oldParseResult = await preEditTreeComputation.value
let parseTransition = IncrementalParseTransition(
previousIncrementalParseResult: oldParseResult,
edits: edits,
reusedNodeCallback: reusedNodeCallback
)
return Parser.parseIncrementally(source: postEditSnapshot.text, parseTransition: parseTransition)
}
self.setComputation(for: postEditSnapshot.id, computation: incrementalParseComputation)
}
}
|
