Xcode: Fix generated references to CMakeLists.txt files

Refactoring in commit 2d888e3390 (cmSourceFile: Rename mutating
GetFullPath() overload, 2019-08-29, v3.16.0-rc1~160^2) accidentally left
the paths to `CMakeLists.txt` files empty in generated Xcode project
files.

Fixes: #19927

Source/cmGlobalXCodeGenerator.cxx

@@ -776,7 +776,7 @@ public:
           "Xcode does not support per-config per-source " << property << ":\n"
           "  " << expression << "\n"
           "specified for source:\n"
-          "  " << this->SourceFile->GetFullPath() << "\n";
+          "  " << this->SourceFile->ResolveFullPath() << "\n";
       /* clang-format on */
       this->LocalGenerator->IssueMessage(MessageType::FATAL_ERROR, e.str());
     }
@@ -850,7 +850,7 @@ cmXCodeObject* cmGlobalXCodeGenerator::CreateXCodeSourceFile(
   lg->AppendFlags(flags, lg->GetIncludeFlags(includes, gtgt, lang, true));
 
   cmXCodeObject* buildFile =
-    this->CreateXCodeSourceFileFromPath(sf->GetFullPath(), gtgt, lang, sf);
+    this->CreateXCodeSourceFileFromPath(sf->ResolveFullPath(), gtgt, lang, sf);
 
   cmXCodeObject* settings = this->CreateObject(cmXCodeObject::ATTRIBUTE_GROUP);
   settings->AddAttributeIfNotEmpty("COMPILER_FLAGS",
@@ -1030,7 +1030,7 @@ cmXCodeObject* cmGlobalXCodeGenerator::CreateXCodeFileReference(
 {
   std::string lang = this->CurrentLocalGenerator->GetSourceFileLanguage(*sf);
 
-  return this->CreateXCodeFileReferenceFromPath(sf->GetFullPath(), target,
+  return this->CreateXCodeFileReferenceFromPath(sf->ResolveFullPath(), target,
                                                 lang, sf);
 }
 
@@ -1065,7 +1065,7 @@ struct cmSourceFilePathCompare
 {
   bool operator()(cmSourceFile* l, cmSourceFile* r)
   {
-    return l->GetFullPath() < r->GetFullPath();
+    return l->ResolveFullPath() < r->ResolveFullPath();
   }
 };
 
@@ -2859,7 +2859,7 @@ bool cmGlobalXCodeGenerator::CreateGroups(
                    "/CMakeLists.txt");
         cmSourceFile* sf = gtgt->Makefile->GetOrCreateSource(
           listfile, false, cmSourceFileLocationKind::Known);
-        addSourceToGroup(sf->GetFullPath());
+        addSourceToGroup(sf->ResolveFullPath());
       }
 
       // Add the Info.plist we are about to generate for an App Bundle.
@@ -2867,7 +2867,7 @@ bool cmGlobalXCodeGenerator::CreateGroups(
         std::string plist = this->ComputeInfoPListLocation(gtgt);
         cmSourceFile* sf = gtgt->Makefile->GetOrCreateSource(
           plist, true, cmSourceFileLocationKind::Known);
-        addSourceToGroup(sf->GetFullPath());
+        addSourceToGroup(sf->ResolveFullPath());
       }
     }
   }

Tests/RunCMake/XcodeProject/ImplicitCMakeLists-check.cmake

@@ -0,0 +1,20 @@
+set(xcProjectFile "${RunCMake_TEST_BINARY_DIR}/ImplicitCMakeLists.xcodeproj/project.pbxproj")
+if(NOT EXISTS "${xcProjectFile}")
+  set(RunCMake_TEST_FAILED "Project file ${xcProjectFile} does not exist.")
+  return()
+endif()
+
+set(foundCMakeLists 0)
+file(STRINGS "${xcProjectFile}" lines)
+foreach(line IN LISTS lines)
+  if(line MATCHES "PBXFileReference.*CMakeLists.txt")
+    if(foundCMakeLists)
+      set(RunCMake_TEST_FAILED "CMakeLists.txt referenced multiple times")
+      return()
+    endif()
+    set(foundCMakeLists 1)
+  endif()
+endforeach()
+if(NOT foundCMakeLists)
+  set(RunCMake_TEST_FAILED "CMakeLists.txt not referenced")
+endif()

Tests/RunCMake/XcodeProject/RunCMakeTest.cmake

@@ -1,6 +1,7 @@
 include(RunCMake)
 
 run_cmake(ExplicitCMakeLists)
+run_cmake(ImplicitCMakeLists)
 
 run_cmake(XcodeFileType)
 run_cmake(XcodeAttributeLocation)