[Format/ObjC] Support NS_ASSUME_NONNULL_BEGIN and FOUNDATION_EXPORT in ObjC language guesser

[benhamilton]

Summary

This adds to the ObjC language guesser a few more common macros used
in ObjC headers. These can help distinguish ObjC headers which
otherwise lack ObjC types from C++ headers.

Contributed by danblakemore.

Tested: New tests included. Ran unit tests with:

% cmake -S llvm -B build -G Ninja && \
  ninja -C build FormatTests && \
  ./build/tools/clang/unittests/Format/FormatTests --gtest_filter="*FormatTestObjC*"

(snip)
[----------] 24 tests from FormatTestObjC (265 ms total)

[----------] Global test environment tear-down
[==========] 26 tests from 2 test suites ran. (270 ms total)
[  PASSED  ] 26 tests.

[benhamilton]

Fix auto-complete-o.

[benhamilton]

Add FOUNDATION_EXPORT alias for FOUNDATION_EXTERN (Apple #defines the former to the latter).

[MyDeveloperDay]

LGTM

clang/lib/Format/Format.cpp

static constexpr llvm::StringLiteral FoundationIdentifiers[] = {
         "CGRectInfinite",
         "CGRectMake",
         "CGRectNull",
         "CGRectZero",
         "CGSize",
         "CGSizeMake",
         "CGVector",
         "CGVectorMake",
+        "FOUNDATION_EXPORT", // This is an alias for FOUNDATION_EXTERN.
+        "FOUNDATION_EXTERN",
         "NSAffineTransform",
         "NSArray",
         "NSAttributedString",
         "NSBlockOperation",
         "NSBundle",
         "NSCache",
         "NSCalendar",
         "NSCharacterSet",
static constexpr llvm::StringLiteral FoundationIdentifiers[] = {
         "NSString",
         "NSTimeZone",
         "NSUInteger",
         "NSURL",
         "NSURLComponents",
         "NSURLQueryItem",
         "NSUUID",
         "NSValue",
+        "NS_ASSUME_NONNULL_BEGIN",
         "UIImage",
         "UIView",
     };
 
     for (auto *Line : AnnotatedLines) {
       if (Line->First && (Line->First->TokenText.startswith("#") ||
                           Line->First->TokenText == "__pragma" ||
                           Line->First->TokenText == "_Pragma")) {

clang/test/Format/dump-config-objc-macros.h

+// RUN: clang-format -dump-config %s | FileCheck %s
+
+// CHECK: Language: ObjC
+NS_ASSUME_NONNULL_BEGIN
+
+FOUNDATION_EXTERN int kConstant;
+
+NS_ASSUME_NONNULL_END

clang/unittests/Format/FormatTestObjC.cpp

TEST(FormatTestObjCStyle, DetectsObjCInHeaders) {
   ASSERT_TRUE((bool)Style);
   EXPECT_EQ(FormatStyle::LK_ObjC, Style->Language);
 
   Style =
       getStyle("{}", "a.h", "none", "typedef NS_ERROR_ENUM(int, Foo) {};\n");
   ASSERT_TRUE((bool)Style);
   EXPECT_EQ(FormatStyle::LK_ObjC, Style->Language);
 
+  Style = getStyle("{}", "a.h", "none", R"objc(
+NS_ASSUME_NONNULL_BEGIN
+extern int i;
+NS_ASSUME_NONNULL_END
+)objc");
+  ASSERT_TRUE((bool)Style);
+  EXPECT_EQ(FormatStyle::LK_ObjC, Style->Language);
+
+  Style = getStyle("{}", "a.h", "none", R"objc(
+FOUNDATION_EXTERN void DoStuff(void);
+)objc");
+  ASSERT_TRUE((bool)Style);
+  EXPECT_EQ(FormatStyle::LK_ObjC, Style->Language);
+
+  Style = getStyle("{}", "a.h", "none", R"objc(
+FOUNDATION_EXPORT void DoStuff(void);
+)objc");
+  ASSERT_TRUE((bool)Style);
+  EXPECT_EQ(FormatStyle::LK_ObjC, Style->Language);
+
   Style = getStyle("{}", "a.h", "none", "enum Foo {};");
   ASSERT_TRUE((bool)Style);
   EXPECT_EQ(FormatStyle::LK_Cpp, Style->Language);
 
   Style =
       getStyle("{}", "a.h", "none", "inline void Foo() { Log(@\"Foo\"); }\n");
   ASSERT_TRUE((bool)Style);
   EXPECT_EQ(FormatStyle::LK_ObjC, Style->Language);