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 
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.
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.
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 
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 
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 
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