1 //===--- Transformer.cpp - Transformer library implementation ---*- 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 "clang/Tooling/Transformer/RewriteRule.h"
10 #include "clang/ASTMatchers/ASTMatchFinder.h"
11 #include "clang/ASTMatchers/ASTMatchers.h"
12 #include "clang/Basic/SourceLocation.h"
13 #include "clang/Tooling/Transformer/SourceCode.h"
14 #include "llvm/ADT/Optional.h"
15 #include "llvm/ADT/StringRef.h"
16 #include "llvm/Support/Errc.h"
17 #include "llvm/Support/Error.h"
18 #include <map>
19 #include <string>
20 #include <utility>
21 #include <vector>
22 
23 using namespace clang;
24 using namespace transformer;
25 
26 using ast_matchers::MatchFinder;
27 using ast_matchers::internal::DynTypedMatcher;
28 
29 using MatchResult = MatchFinder::MatchResult;
30 
31 static Expected<SmallVector<transformer::Edit, 1>>
32 translateEdits(const MatchResult &Result, ArrayRef<ASTEdit> ASTEdits) {
33   SmallVector<transformer::Edit, 1> Edits;
34   for (const auto &E : ASTEdits) {
35     Expected<CharSourceRange> Range = E.TargetRange(Result);
36     if (!Range)
37       return Range.takeError();
38     llvm::Optional<CharSourceRange> EditRange =
39         tooling::getRangeForEdit(*Range, *Result.Context);
40     // FIXME: let user specify whether to treat this case as an error or ignore
41     // it as is currently done.
42     if (!EditRange)
43       return SmallVector<Edit, 0>();
44     auto Replacement = E.Replacement->eval(Result);
45     if (!Replacement)
46       return Replacement.takeError();
47     auto Metadata = E.Metadata(Result);
48     if (!Metadata)
49       return Metadata.takeError();
50     transformer::Edit T;
51     T.Range = *EditRange;
52     T.Replacement = std::move(*Replacement);
53     T.Metadata = std::move(*Metadata);
54     Edits.push_back(std::move(T));
55   }
56   return Edits;
57 }
58 
59 EditGenerator transformer::editList(SmallVector<ASTEdit, 1> Edits) {
60   return [Edits = std::move(Edits)](const MatchResult &Result) {
61     return translateEdits(Result, Edits);
62   };
63 }
64 
65 EditGenerator transformer::edit(ASTEdit Edit) {
66   return [Edit = std::move(Edit)](const MatchResult &Result) {
67     return translateEdits(Result, {Edit});
68   };
69 }
70 
71 ASTEdit transformer::changeTo(RangeSelector Target, TextGenerator Replacement) {
72   ASTEdit E;
73   E.TargetRange = std::move(Target);
74   E.Replacement = std::move(Replacement);
75   return E;
76 }
77 
78 namespace {
79 /// A \c TextGenerator that always returns a fixed string.
80 class SimpleTextGenerator : public MatchComputation<std::string> {
81   std::string S;
82 
83 public:
84   SimpleTextGenerator(std::string S) : S(std::move(S)) {}
85   llvm::Error eval(const ast_matchers::MatchFinder::MatchResult &,
86                    std::string *Result) const override {
87     Result->append(S);
88     return llvm::Error::success();
89   }
90   std::string toString() const override {
91     return (llvm::Twine("text(\"") + S + "\")").str();
92   }
93 };
94 } // namespace
95 
96 ASTEdit transformer::remove(RangeSelector S) {
97   return change(std::move(S), std::make_shared<SimpleTextGenerator>(""));
98 }
99 
100 RewriteRule transformer::makeRule(ast_matchers::internal::DynTypedMatcher M,
101                                   EditGenerator Edits,
102                                   TextGenerator Explanation) {
103   return RewriteRule{{RewriteRule::Case{
104       std::move(M), std::move(Edits), std::move(Explanation), {}}}};
105 }
106 
107 void transformer::addInclude(RewriteRule &Rule, StringRef Header,
108                          IncludeFormat Format) {
109   for (auto &Case : Rule.Cases)
110     Case.AddedIncludes.emplace_back(Header.str(), Format);
111 }
112 
113 #ifndef NDEBUG
114 // Filters for supported matcher kinds. FIXME: Explicitly list the allowed kinds
115 // (all node matcher types except for `QualType` and `Type`), rather than just
116 // banning `QualType` and `Type`.
117 static bool hasValidKind(const DynTypedMatcher &M) {
118   return !M.canConvertTo<QualType>();
119 }
120 #endif
121 
122 // Binds each rule's matcher to a unique (and deterministic) tag based on
123 // `TagBase` and the id paired with the case. All of the returned matchers have
124 // their traversal kind explicitly set, either based on a pre-set kind or to the
125 // provided `DefaultTraversalKind`.
126 static std::vector<DynTypedMatcher> taggedMatchers(
127     StringRef TagBase,
128     const SmallVectorImpl<std::pair<size_t, RewriteRule::Case>> &Cases,
129     ast_type_traits::TraversalKind DefaultTraversalKind) {
130   std::vector<DynTypedMatcher> Matchers;
131   Matchers.reserve(Cases.size());
132   for (const auto &Case : Cases) {
133     std::string Tag = (TagBase + Twine(Case.first)).str();
134     // HACK: Many matchers are not bindable, so ensure that tryBind will work.
135     DynTypedMatcher BoundMatcher(Case.second.Matcher);
136     BoundMatcher.setAllowBind(true);
137     auto M = *BoundMatcher.tryBind(Tag);
138     Matchers.push_back(!M.getTraversalKind()
139                            ? M.withTraversalKind(DefaultTraversalKind)
140                            : std::move(M));
141   }
142   return Matchers;
143 }
144 
145 // Simply gathers the contents of the various rules into a single rule. The
146 // actual work to combine these into an ordered choice is deferred to matcher
147 // registration.
148 RewriteRule transformer::applyFirst(ArrayRef<RewriteRule> Rules) {
149   RewriteRule R;
150   for (auto &Rule : Rules)
151     R.Cases.append(Rule.Cases.begin(), Rule.Cases.end());
152   return R;
153 }
154 
155 std::vector<DynTypedMatcher>
156 transformer::detail::buildMatchers(const RewriteRule &Rule) {
157   // Map the cases into buckets of matchers -- one for each "root" AST kind,
158   // which guarantees that they can be combined in a single anyOf matcher. Each
159   // case is paired with an identifying number that is converted to a string id
160   // in `taggedMatchers`.
161   std::map<ASTNodeKind, SmallVector<std::pair<size_t, RewriteRule::Case>, 1>>
162       Buckets;
163   const SmallVectorImpl<RewriteRule::Case> &Cases = Rule.Cases;
164   for (int I = 0, N = Cases.size(); I < N; ++I) {
165     assert(hasValidKind(Cases[I].Matcher) &&
166            "Matcher must be non-(Qual)Type node matcher");
167     Buckets[Cases[I].Matcher.getSupportedKind()].emplace_back(I, Cases[I]);
168   }
169 
170   // Each anyOf explicitly controls the traversal kind. The anyOf itself is set
171   // to `TK_AsIs` to ensure no nodes are skipped, thereby deferring to the kind
172   // of the branches. Then, each branch is either left as is, if the kind is
173   // already set, or explicitly set to `TK_IgnoreUnlessSpelledInSource`. We
174   // choose this setting, because we think it is the one most friendly to
175   // beginners, who are (largely) the target audience of Transformer.
176   std::vector<DynTypedMatcher> Matchers;
177   for (const auto &Bucket : Buckets) {
178     DynTypedMatcher M = DynTypedMatcher::constructVariadic(
179         DynTypedMatcher::VO_AnyOf, Bucket.first,
180         taggedMatchers("Tag", Bucket.second, TK_IgnoreUnlessSpelledInSource));
181     M.setAllowBind(true);
182     // `tryBind` is guaranteed to succeed, because `AllowBind` was set to true.
183     Matchers.push_back(
184         M.tryBind(RewriteRule::RootID)->withTraversalKind(TK_AsIs));
185   }
186   return Matchers;
187 }
188 
189 DynTypedMatcher transformer::detail::buildMatcher(const RewriteRule &Rule) {
190   std::vector<DynTypedMatcher> Ms = buildMatchers(Rule);
191   assert(Ms.size() == 1 && "Cases must have compatible matchers.");
192   return Ms[0];
193 }
194 
195 SourceLocation transformer::detail::getRuleMatchLoc(const MatchResult &Result) {
196   auto &NodesMap = Result.Nodes.getMap();
197   auto Root = NodesMap.find(RewriteRule::RootID);
198   assert(Root != NodesMap.end() && "Transformation failed: missing root node.");
199   llvm::Optional<CharSourceRange> RootRange = tooling::getRangeForEdit(
200       CharSourceRange::getTokenRange(Root->second.getSourceRange()),
201       *Result.Context);
202   if (RootRange)
203     return RootRange->getBegin();
204   // The match doesn't have a coherent range, so fall back to the expansion
205   // location as the "beginning" of the match.
206   return Result.SourceManager->getExpansionLoc(
207       Root->second.getSourceRange().getBegin());
208 }
209 
210 // Finds the case that was "selected" -- that is, whose matcher triggered the
211 // `MatchResult`.
212 const RewriteRule::Case &
213 transformer::detail::findSelectedCase(const MatchResult &Result,
214                                   const RewriteRule &Rule) {
215   if (Rule.Cases.size() == 1)
216     return Rule.Cases[0];
217 
218   auto &NodesMap = Result.Nodes.getMap();
219   for (size_t i = 0, N = Rule.Cases.size(); i < N; ++i) {
220     std::string Tag = ("Tag" + Twine(i)).str();
221     if (NodesMap.find(Tag) != NodesMap.end())
222       return Rule.Cases[i];
223   }
224   llvm_unreachable("No tag found for this rule.");
225 }
226 
227 constexpr llvm::StringLiteral RewriteRule::RootID;
228 
229 TextGenerator tooling::text(std::string M) {
230   return std::make_shared<SimpleTextGenerator>(std::move(M));
231 }
232