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