1//===--- HeaderSourceSwitch.cpp - --------------------------------*- C++-*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#include "HeaderSourceSwitch.h"
10#include "AST.h"
11#include "SourceCode.h"
12#include "index/SymbolCollector.h"
13#include "support/Logger.h"
14#include "support/Path.h"
15#include "clang/AST/Decl.h"
16#include <optional>
17
18namespace clang {
19namespace clangd {
20
21std::optional<Path> getCorrespondingHeaderOrSource(
22 PathRef OriginalFile, llvm::IntrusiveRefCntPtr<llvm::vfs::FileSystem> VFS) {
23 llvm::StringRef SourceExtensions[] = {".cpp", ".c", ".cc", ".cxx",
24 ".c++", ".m", ".mm"};
25 llvm::StringRef HeaderExtensions[] = {".h", ".hh", ".hpp", ".hxx", ".inc"};
26
27 llvm::StringRef PathExt = llvm::sys::path::extension(path: OriginalFile);
28
29 // Lookup in a list of known extensions.
30 bool IsSource = llvm::any_of(Range&: SourceExtensions, P: [&PathExt](PathRef SourceExt) {
31 return SourceExt.equals_insensitive(RHS: PathExt);
32 });
33
34 bool IsHeader = llvm::any_of(Range&: HeaderExtensions, P: [&PathExt](PathRef HeaderExt) {
35 return HeaderExt.equals_insensitive(RHS: PathExt);
36 });
37
38 // We can only switch between the known extensions.
39 if (!IsSource && !IsHeader)
40 return std::nullopt;
41
42 // Array to lookup extensions for the switch. An opposite of where original
43 // extension was found.
44 llvm::ArrayRef<llvm::StringRef> NewExts;
45 if (IsSource)
46 NewExts = HeaderExtensions;
47 else
48 NewExts = SourceExtensions;
49
50 // Storage for the new path.
51 llvm::SmallString<128> NewPath = OriginalFile;
52
53 // Loop through switched extension candidates.
54 for (llvm::StringRef NewExt : NewExts) {
55 llvm::sys::path::replace_extension(path&: NewPath, extension: NewExt);
56 if (VFS->exists(Path: NewPath))
57 return Path(NewPath);
58
59 // Also check NewExt in upper-case, just in case.
60 llvm::sys::path::replace_extension(path&: NewPath, extension: NewExt.upper());
61 if (VFS->exists(Path: NewPath))
62 return Path(NewPath);
63 }
64 return std::nullopt;
65}
66
67std::optional<Path> getCorrespondingHeaderOrSource(PathRef OriginalFile,
68 ParsedAST &AST,
69 const SymbolIndex *Index) {
70 if (!Index) {
71 // FIXME: use the AST to do the inference.
72 return std::nullopt;
73 }
74 LookupRequest Request;
75 // Find all symbols present in the original file.
76 for (const auto *D : getIndexableLocalDecls(AST)) {
77 if (auto ID = getSymbolID(D))
78 Request.IDs.insert(V: ID);
79 }
80 llvm::StringMap<int> Candidates; // Target path => score.
81 auto AwardTarget = [&](const char *TargetURI) {
82 if (auto TargetPath = URI::resolve(FileURI: TargetURI, HintPath: OriginalFile)) {
83 if (!pathEqual(*TargetPath, OriginalFile)) // exclude the original file.
84 ++Candidates[*TargetPath];
85 } else {
86 elog(Fmt: "Failed to resolve URI {0}: {1}", Vals&: TargetURI, Vals: TargetPath.takeError());
87 }
88 };
89 // If we switch from a header, we are looking for the implementation
90 // file, so we use the definition loc; otherwise we look for the header file,
91 // we use the decl loc;
92 //
93 // For each symbol in the original file, we get its target location (decl or
94 // def) from the index, then award that target file.
95 bool IsHeader = isHeaderFile(FileName: OriginalFile, LangOpts: AST.getLangOpts());
96 Index->lookup(Req: Request, Callback: [&](const Symbol &Sym) {
97 if (IsHeader)
98 AwardTarget(Sym.Definition.FileURI);
99 else
100 AwardTarget(Sym.CanonicalDeclaration.FileURI);
101 });
102 // FIXME: our index doesn't have any interesting information (this could be
103 // that the background-index is not finished), we should use the decl/def
104 // locations from the AST to do the inference (from .cc to .h).
105 if (Candidates.empty())
106 return std::nullopt;
107
108 // Pickup the winner, who contains most of symbols.
109 // FIXME: should we use other signals (file proximity) to help score?
110 auto Best = Candidates.begin();
111 for (auto It = Candidates.begin(); It != Candidates.end(); ++It) {
112 if (It->second > Best->second)
113 Best = It;
114 else if (It->second == Best->second && It->first() < Best->first())
115 // Select the first one in the lexical order if we have multiple
116 // candidates.
117 Best = It;
118 }
119 return Path(Best->first());
120}
121
122std::vector<const Decl *> getIndexableLocalDecls(ParsedAST &AST) {
123 std::vector<const Decl *> Results;
124 std::function<void(Decl *)> TraverseDecl = [&](Decl *D) {
125 auto *ND = llvm::dyn_cast<NamedDecl>(Val: D);
126 if (!ND || ND->isImplicit())
127 return;
128 if (!SymbolCollector::shouldCollectSymbol(ND: *ND, ASTCtx: D->getASTContext(), Opts: {},
129 /*IsMainFileSymbol=*/false))
130 return;
131 if (!llvm::isa<FunctionDecl>(Val: ND)) {
132 // Visit the children, but we skip function decls as we are not interested
133 // in the function body.
134 if (auto *Scope = llvm::dyn_cast<DeclContext>(Val: ND)) {
135 for (auto *D : Scope->decls())
136 TraverseDecl(D);
137 }
138 }
139 if (llvm::isa<NamespaceDecl>(Val: D))
140 return; // namespace is indexable, but we're not interested.
141 Results.push_back(x: D);
142 };
143 // Traverses the ParsedAST directly to collect all decls present in the main
144 // file.
145 for (auto *TopLevel : AST.getLocalTopLevelDecls())
146 TraverseDecl(TopLevel);
147 return Results;
148}
149
150} // namespace clangd
151} // namespace clang
152