[clangd] Dont index ObjCCategoryDecls for completion

[kadircet]

Summary

They are already provided by Sema, deserializing from preamble if need
be. Moreover category names are meaningless outside interface/implementation
context, hence they were only causing noise.

[dgoldman]

clang-tools-extra/clangd/CodeComplete.cpp

1918

Seems like we should also ignore ObjCCategoryImplDecl, I think those would have the same issue (although only from other .m files in the project, not from SDK headers)?

[kadircet]

• Also handle ObjcCategoryImplDecl

clang-tools-extra/clangd/CodeComplete.cpp

1918

we actually never index those, as symbolcollector canonicalizes ObjcCategoryImplDecls to ObjcCategoryDecl, so we can't really test it. but adding here for completeness.

clang-tools-extra/clangd/CodeComplete.cpp

 #include "clang/Sema/DeclSpec.h"
 #include "clang/Sema/Sema.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Casting.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/ScopedPrinter.h"
 #include <algorithm>
 #include <iterator>
auto InTopLevelScope = [](const NamedDecl &ND) {
     };
     return false;
   };
   // We only complete symbol's name, which is the same as the name of the
   // *primary* template in case of template specializations.
   if (isExplicitTemplateSpecialization(&ND))
     return false;
 
+  // Category decls are not useful on their own outside the interface or
+  // implementation blocks. Moreover, sema already provides completion for
+  // these, even if it requires preamble deserialization. So by excluding them
+  // from the index, we reduce the noise in all the other completion scopes.
+  if (llvm::isa<ObjCCategoryDecl>(&ND))
+    return false;
+
   if (InTopLevelScope(ND))
     return true;
 
   if (const auto *EnumDecl = dyn_cast<clang::EnumDecl>(ND.getDeclContext()))
     return InTopLevelScope(*EnumDecl) && !EnumDecl->isScoped();
 
   return false;
 }

clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp

TEST(CompletionTest, NoCrashDueToMacroOrdering) {
   EXPECT_THAT(completions(R"cpp(
     #define ECHO(X) X
     #define ECHO2(X) ECHO(X)
     int finish_preamble = EC^HO(2);)cpp")
                   .Completions,
               UnorderedElementsAre(Labeled("ECHO(X)"), Labeled("ECHO2(X)")));
 }
 
+TEST(CompletionTest, ObjCCategoryDecls) {
+  TestTU TU;
+  TU.ExtraArgs.push_back("-xobjective-c");
+  TU.HeaderCode = R"objc(
+  @interface Foo
+  @end
+
+  @interface Foo (FooExt1)
+  @end
+
+  @interface Foo (FooExt2)
+  @end
+
+  @interface Bar
+  @end
+
+  @interface Bar (BarExt)
+  @end)objc";
+
+  {
+    Annotations Test(R"objc(
+  @implementation Foo (^)
+  @end
+  )objc");
+    TU.Code = Test.code().str();
+    auto Results = completions(TU, Test.point());
+    EXPECT_THAT(Results.Completions,
+                UnorderedElementsAre(Labeled("FooExt1"), Labeled("FooExt2")));
+  }
+  {
+    Annotations Test(R"objc(
+  @interface Foo (^)
+  @end
+  )objc");
+    TU.Code = Test.code().str();
+    auto Results = completions(TU, Test.point());
+    EXPECT_THAT(Results.Completions, UnorderedElementsAre(Labeled("BarExt")));
+  }
+}
 } // namespace
 } // namespace clangd
 } // namespace clang

clang-tools-extra/clangd/unittests/SymbolCollectorTests.cpp

const std::string Header = R"(
     - (void)someMethodName3:(void*)name3;
     @end
   )";
   TestFileName = testPath("test.m");
   runSymbolCollector(Header, /*Main=*/"", {"-fblocks", "-xobjective-c++"});
   EXPECT_THAT(Symbols,
               UnorderedElementsAre(
                   QName("Person"), QName("Person::someMethodName:lastName:"),
-                  QName("MyCategory"), QName("Person::someMethodName2:"),
-                  QName("MyProtocol"), QName("MyProtocol::someMethodName3:")));
+                  AllOf(QName("MyCategory"), ForCodeCompletion(false)),
+                  QName("Person::someMethodName2:"), QName("MyProtocol"),
+                  QName("MyProtocol::someMethodName3:")));
 }
 
 TEST_F(SymbolCollectorTest, ObjCPropertyImpl) {
   const std::string Header = R"(
     @interface Container
     @property(nonatomic) int magic;
     @end