Fix Firestore compilation under Xcode < 9.2 (#1367)

* Don't rely on specialization failure to determine when std::hash is unavailable.

Instead manually declare the conditions under which std::hash should be
defined.

* Fix detection of Objective-C classes in Xcode < 9.2

std::is_base_of<NSObject, NSString>{} is false there so the overloads
defined for Objective-C types weren't getting enabled.

* Add explicit tests for StringFormat using Objective-C objects

* Add explicit tests for HasStdHash

1 files changed, 8 insertions, 0 deletions

diff --git a/Firestore/Example/Firestore.xcodeproj/project.pbxproj b/Firestore/Example/Firestore.xcodeproj/project.pbxproj
index ca8b598..9207ad2 100644
--- a/Firestore/Example/Firestore.xcodeproj/project.pbxproj
+++ b/Firestore/Example/Firestore.xcodeproj/project.pbxproj
@@ -24,6 +24,7 @@
 /* End PBXAggregateTarget section */
 
 /* Begin PBXBuildFile section */
+		0535C1B65DADAE1CE47FA3CA /* string_format_apple_test.mm in Sources */ = {isa = PBXBuildFile; fileRef = 9CFD366B783AE27B9E79EE7A /* string_format_apple_test.mm */; };
 		132E3E53179DE287D875F3F2 /* FSTLevelDBTransactionTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = 132E36BB104830BD806351AC /* FSTLevelDBTransactionTests.mm */; };
 		3B843E4C1F3A182900548890 /* remote_store_spec_test.json in Resources */ = {isa = PBXBuildFile; fileRef = 3B843E4A1F3930A400548890 /* remote_store_spec_test.json */; };
 		54131E9720ADE679001DF3FF /* string_format_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = 54131E9620ADE678001DF3FF /* string_format_test.cc */; };
@@ -180,6 +181,7 @@
 		B6FB4690208F9BB300554BA2 /* executor_test.cc in Sources */ = {isa = PBXBuildFile; fileRef = B6FB4688208F9B9100554BA2 /* executor_test.cc */; };
 		BF219E98F1C5A1DAEB5EEC86 /* Pods_Firestore_Example_iOS_SwiftBuildTest.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 379B34A1536045869826D82A /* Pods_Firestore_Example_iOS_SwiftBuildTest.framework */; };
 		C1AA536F90A0A576CA2816EB /* Pods_Firestore_Example_iOS_Firestore_SwiftTests_iOS.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = BB92EB03E3F92485023F64ED /* Pods_Firestore_Example_iOS_Firestore_SwiftTests_iOS.framework */; };
+		C80B10E79CDD7EF7843C321E /* type_traits_apple_test.mm in Sources */ = {isa = PBXBuildFile; fileRef = 2A0CF41BA5AED6049B0BEB2C /* type_traits_apple_test.mm */; };
 		C8D3CE2343E53223E6487F2C /* Pods_Firestore_Example_iOS.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 5918805E993304321A05E82B /* Pods_Firestore_Example_iOS.framework */; };
 		DE03B2D41F2149D600A30B9C /* XCTest.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 6003F5AF195388D20070C39A /* XCTest.framework */; };
 		DE03B2D51F2149D600A30B9C /* UIKit.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 6003F591195388D20070C39A /* UIKit.framework */; };
@@ -251,6 +253,7 @@
 		1277F98C20D2DF0867496976 /* Pods-Firestore_IntegrationTests_iOS.debug.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Firestore_IntegrationTests_iOS.debug.xcconfig"; path = "Pods/Target Support Files/Pods-Firestore_IntegrationTests_iOS/Pods-Firestore_IntegrationTests_iOS.debug.xcconfig"; sourceTree = "<group>"; };
 		12F4357299652983A615F886 /* LICENSE */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text; name = LICENSE; path = ../LICENSE; sourceTree = "<group>"; };
 		132E36BB104830BD806351AC /* FSTLevelDBTransactionTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = FSTLevelDBTransactionTests.mm; sourceTree = "<group>"; };
+		2A0CF41BA5AED6049B0BEB2C /* type_traits_apple_test.mm */ = {isa = PBXFileReference; includeInIndex = 1; path = type_traits_apple_test.mm; sourceTree = "<group>"; };
 		2B50B3A0DF77100EEE887891 /* Pods_Firestore_Tests_iOS.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Pods_Firestore_Tests_iOS.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		379B34A1536045869826D82A /* Pods_Firestore_Example_iOS_SwiftBuildTest.framework */ = {isa = PBXFileReference; explicitFileType = wrapper.framework; includeInIndex = 0; path = Pods_Firestore_Example_iOS_SwiftBuildTest.framework; sourceTree = BUILT_PRODUCTS_DIR; };
 		3B843E4A1F3930A400548890 /* remote_store_spec_test.json */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text.json; path = remote_store_spec_test.json; sourceTree = "<group>"; };
@@ -399,6 +402,7 @@
 		74ACEC3603BE58B57A7E8D4C /* Pods-Firestore_Example_iOS-SwiftBuildTest.release.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-Firestore_Example_iOS-SwiftBuildTest.release.xcconfig"; path = "Pods/Target Support Files/Pods-Firestore_Example_iOS-SwiftBuildTest/Pods-Firestore_Example_iOS-SwiftBuildTest.release.xcconfig"; sourceTree = "<group>"; };
 		873B8AEA1B1F5CCA007FD442 /* Main.storyboard */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = file.storyboard; name = Main.storyboard; path = Base.lproj/Main.storyboard; sourceTree = "<group>"; };
 		8E002F4AD5D9B6197C940847 /* Firestore.podspec */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text; name = Firestore.podspec; path = ../Firestore.podspec; sourceTree = "<group>"; };
+		9CFD366B783AE27B9E79EE7A /* string_format_apple_test.mm */ = {isa = PBXFileReference; includeInIndex = 1; path = string_format_apple_test.mm; sourceTree = "<group>"; };
 		AB356EF6200EA5EB0089B766 /* field_value_test.cc */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = field_value_test.cc; sourceTree = "<group>"; };
 		AB380CF82019382300D97691 /* target_id_generator_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = target_id_generator_test.cc; sourceTree = "<group>"; };
 		AB380CFC201A2EE200D97691 /* string_util_test.cc */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = string_util_test.cc; sourceTree = "<group>"; };
@@ -558,8 +562,10 @@
 				54A0352C20A3B3D7003E0143 /* status_test.cc */,
 				54A0352B20A3B3D7003E0143 /* status_test_util.h */,
 				54A0352D20A3B3D7003E0143 /* statusor_test.cc */,
+				9CFD366B783AE27B9E79EE7A /* string_format_apple_test.mm */,
 				54131E9620ADE678001DF3FF /* string_format_test.cc */,
 				AB380CFC201A2EE200D97691 /* string_util_test.cc */,
+				2A0CF41BA5AED6049B0BEB2C /* type_traits_apple_test.mm */,
 			);
 			path = util;
 			sourceTree = "<group>";
@@ -1557,6 +1563,7 @@
 				549CCA5020A36DBC00BCEB75 /* sorted_set_test.cc in Sources */,
 				54A0352F20A3B3D8003E0143 /* status_test.cc in Sources */,
 				54A0353020A3B3D8003E0143 /* statusor_test.cc in Sources */,
+				0535C1B65DADAE1CE47FA3CA /* string_format_apple_test.mm in Sources */,
 				54131E9720ADE679001DF3FF /* string_format_test.cc in Sources */,
 				AB380CFE201A2F4500D97691 /* string_util_test.cc in Sources */,
 				AB380CFB2019388600D97691 /* target_id_generator_test.cc in Sources */,
@@ -1565,6 +1572,7 @@
 				ABC1D7E12023A40C00BA84F0 /* token_test.cc in Sources */,
 				54A0352720A3AED0003E0143 /* transform_operations_test.mm in Sources */,
 				549CCA5120A36DBC00BCEB75 /* tree_sorted_map_test.cc in Sources */,
+				C80B10E79CDD7EF7843C321E /* type_traits_apple_test.mm in Sources */,
 				ABC1D7DE2023A05300BA84F0 /* user_test.cc in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;