1 //===--- AvoidNSObjectNewCheck.cpp - clang-tidy ---------------------------===//
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 "AvoidNSObjectNewCheck.h"
10 #include "clang/AST/ASTContext.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "clang/Basic/LangOptions.h"
13 #include "clang/Basic/SourceLocation.h"
14 #include "clang/Basic/SourceManager.h"
15 #include "clang/Lex/Lexer.h"
16 #include "llvm/Support/FormatVariadic.h"
17 #include <map>
18 #include <string>
19
20 using namespace clang::ast_matchers;
21
22 namespace clang {
23 namespace tidy {
24 namespace google {
25 namespace objc {
26
isMessageExpressionInsideMacro(const ObjCMessageExpr * Expr)27 static bool isMessageExpressionInsideMacro(const ObjCMessageExpr *Expr) {
28 SourceLocation ReceiverLocation = Expr->getReceiverRange().getBegin();
29 if (ReceiverLocation.isMacroID())
30 return true;
31
32 SourceLocation SelectorLocation = Expr->getSelectorStartLoc();
33 if (SelectorLocation.isMacroID())
34 return true;
35
36 return false;
37 }
38
39 // Walk up the class hierarchy looking for an -init method, returning true
40 // if one is found and has not been marked unavailable.
isInitMethodAvailable(const ObjCInterfaceDecl * ClassDecl)41 static bool isInitMethodAvailable(const ObjCInterfaceDecl *ClassDecl) {
42 while (ClassDecl != nullptr) {
43 for (const auto *MethodDecl : ClassDecl->instance_methods()) {
44 if (MethodDecl->getSelector().getAsString() == "init")
45 return !MethodDecl->isUnavailable();
46 }
47 ClassDecl = ClassDecl->getSuperClass();
48 }
49
50 // No -init method found in the class hierarchy. This should occur only rarely
51 // in Objective-C code, and only really applies to classes not derived from
52 // NSObject.
53 return false;
54 }
55
56 // Returns the string for the Objective-C message receiver. Keeps any generics
57 // included in the receiver class type, which are stripped if the class type is
58 // used. While the generics arguments will not make any difference to the
59 // returned code at this time, the style guide allows them and they should be
60 // left in any fix-it hint.
getReceiverString(SourceRange ReceiverRange,const SourceManager & SM,const LangOptions & LangOpts)61 static StringRef getReceiverString(SourceRange ReceiverRange,
62 const SourceManager &SM,
63 const LangOptions &LangOpts) {
64 CharSourceRange CharRange = Lexer::makeFileCharRange(
65 CharSourceRange::getTokenRange(ReceiverRange), SM, LangOpts);
66 return Lexer::getSourceText(CharRange, SM, LangOpts);
67 }
68
getCallFixItHint(const ObjCMessageExpr * Expr,const SourceManager & SM,const LangOptions & LangOpts)69 static FixItHint getCallFixItHint(const ObjCMessageExpr *Expr,
70 const SourceManager &SM,
71 const LangOptions &LangOpts) {
72 // Check whether the messaged class has a known factory method to use instead
73 // of -init.
74 StringRef Receiver =
75 getReceiverString(Expr->getReceiverRange(), SM, LangOpts);
76 // Some classes should use standard factory methods instead of alloc/init.
77 std::map<StringRef, StringRef> ClassToFactoryMethodMap = {{"NSDate", "date"},
78 {"NSNull", "null"}};
79 auto FoundClassFactory = ClassToFactoryMethodMap.find(Receiver);
80 if (FoundClassFactory != ClassToFactoryMethodMap.end()) {
81 StringRef ClassName = FoundClassFactory->first;
82 StringRef FactorySelector = FoundClassFactory->second;
83 std::string NewCall =
84 std::string(llvm::formatv("[{0} {1}]", ClassName, FactorySelector));
85 return FixItHint::CreateReplacement(Expr->getSourceRange(), NewCall);
86 }
87
88 if (isInitMethodAvailable(Expr->getReceiverInterface())) {
89 std::string NewCall =
90 std::string(llvm::formatv("[[{0} alloc] init]", Receiver));
91 return FixItHint::CreateReplacement(Expr->getSourceRange(), NewCall);
92 }
93
94 return {}; // No known replacement available.
95 }
96
registerMatchers(MatchFinder * Finder)97 void AvoidNSObjectNewCheck::registerMatchers(MatchFinder *Finder) {
98 // Add two matchers, to catch calls to +new and implementations of +new.
99 Finder->addMatcher(
100 objcMessageExpr(isClassMessage(), hasSelector("new")).bind("new_call"),
101 this);
102 Finder->addMatcher(
103 objcMethodDecl(isClassMethod(), isDefinition(), hasName("new"))
104 .bind("new_override"),
105 this);
106 }
107
check(const MatchFinder::MatchResult & Result)108 void AvoidNSObjectNewCheck::check(const MatchFinder::MatchResult &Result) {
109 if (const auto *CallExpr =
110 Result.Nodes.getNodeAs<ObjCMessageExpr>("new_call")) {
111 // Don't warn if the call expression originates from a macro expansion.
112 if (isMessageExpressionInsideMacro(CallExpr))
113 return;
114
115 diag(CallExpr->getExprLoc(), "do not create objects with +new")
116 << getCallFixItHint(CallExpr, *Result.SourceManager,
117 Result.Context->getLangOpts());
118 }
119
120 if (const auto *DeclExpr =
121 Result.Nodes.getNodeAs<ObjCMethodDecl>("new_override")) {
122 diag(DeclExpr->getBeginLoc(), "classes should not override +new");
123 }
124 }
125
126 } // namespace objc
127 } // namespace google
128 } // namespace tidy
129 } // namespace clang
130