LYN-2726 Updated the Settings Registry Merge Utils logic to determine

the project root and engine root to fix issues with running the Editor
or AssetProcessor from within the project folder overriding the
project_path with the engine root bootstrap.cfg project_path entry

The order in which the project path is overridden as follows
1. The <engine-root>/bootstrap.cfg is first merged into the Settings
   Registry. Any '/Amazon/AzCore/Bootstrap/project_path' would be used
   if the following steps don't override that key.
2. Followed by general *.setreg/*.setregpatch files being merged into
   the Settings Registry which can override the
   '/Amazon/AzCore/Bootstrap/project_path' key
3. Next a project.json file searched upwards from the current executable
   directory to determine the project path
4. Finally if a command line parameter that overrides the project path
   is supplied it is used instead

Code/Framework/AzCore/AzCore/Component/ComponentApplication.cpp

@@ -178,14 +178,16 @@ namespace AZ
     //! on an update to '/Amazon/AzCore/Bootstrap/project_path' key.
     struct UpdateProjectSettingsEventHandler
     {
-        UpdateProjectSettingsEventHandler(AZ::SettingsRegistryInterface& registry)
+        UpdateProjectSettingsEventHandler(AZ::SettingsRegistryInterface& registry, AZ::CommandLine& commandLine)
             : m_registry{ registry }
+            , m_commandLine{ commandLine }
         {
         }
 
         void operator()(AZStd::string_view path, AZ::SettingsRegistryInterface::Type)
         {
             using FixedValueString = AZ::SettingsRegistryInterface::FixedValueString;
+            // #1 Update the project settings when the project path is set
             const auto projectPathKey = FixedValueString(AZ::SettingsRegistryMergeUtils::BootstrapSettingsRootKey) + "/project_path";
             AZ::IO::FixedMaxPath newProjectPath;
             if (SettingsRegistryMergeUtils::IsPathAncestorDescendantOrEqual(projectPathKey, path)
@@ -194,6 +196,7 @@ namespace AZ
                 UpdateProjectSettingsFromProjectPath(AZ::IO::PathView(newProjectPath));
             }
 
+            // #2 Update the project specialization when the project name is set
             const auto projectNameKey = FixedValueString(AZ::SettingsRegistryMergeUtils::ProjectSettingsRootKey) + "/project_name";
             FixedValueString newProjectName;
             if (SettingsRegistryMergeUtils::IsPathAncestorDescendantOrEqual(projectNameKey, path)
@@ -201,6 +204,12 @@ namespace AZ
             {
                 UpdateProjectSpecializationFromProjectName(newProjectName);
             }
+
+            // #3 Update the ComponentApplication CommandLine instance when the command line settings are merged into the Settings Registry
+            if (path == AZ::SettingsRegistryMergeUtils::CommandLineValueChangedKey)
+            {
+                UpdateCommandLine();
+            }
         }
 
         //! Add the project name as a specialization underneath the /Amazon/AzCore/Settings/Specializations path
@@ -233,10 +242,16 @@ namespace AZ
             AZ::SettingsRegistryMergeUtils::MergeSettingsToRegistry_AddRuntimeFilePaths(m_registry);
         }
 
+        void UpdateCommandLine()
+        {
+            AZ::SettingsRegistryMergeUtils::GetCommandLineFromRegistry(m_registry, m_commandLine);
+        }
+
     private:
         AZ::IO::FixedMaxPath m_oldProjectPath;
         AZ::SettingsRegistryInterface::FixedValueString m_oldProjectName;
         AZ::SettingsRegistryInterface& m_registry;
+        AZ::CommandLine& m_commandLine;
     };
 
     void ComponentApplication::Descriptor::AllocatorRemapping::Reflect(ReflectContext* context, ComponentApplication* app)
@@ -415,6 +430,12 @@ namespace AZ
         // Add the Command Line arguments into the SettingsRegistry
         SettingsRegistryMergeUtils::StoreCommandLineToRegistry(*m_settingsRegistry, m_commandLine);
 
+        // Add a notifier to update the project_settings when
+        // 1. The 'project_path' key changes
+        // 2. The project specialization when the 'project-name' key changes
+        // 3. The ComponentApplication command line when the command line is stored to the registry
+        m_projectChangedHandler = m_settingsRegistry->RegisterNotifier(UpdateProjectSettingsEventHandler{ *m_settingsRegistry, m_commandLine });
+
         // Merge Command Line arguments
         constexpr bool executeRegDumpCommands = false;
         SettingsRegistryMergeUtils::MergeSettingsToRegistry_CommandLine(*m_settingsRegistry, m_commandLine, executeRegDumpCommands);
@@ -429,10 +450,6 @@ namespace AZ
         // for the application root.
         CalculateAppRoot();
 
-        // Add a notifier to update the /Amazon/AzCore/Settings/Specializations
-        // when the 'project_path' property changes within the SettingsRegistry
-        m_projectChangedHandler = m_settingsRegistry->RegisterNotifier(UpdateProjectSettingsEventHandler{ *m_settingsRegistry });
-
         // Merge the bootstrap.cfg file into the Settings Registry as soon as the OSAllocator has been created.
         SettingsRegistryMergeUtils::MergeSettingsToRegistry_Bootstrap(*m_settingsRegistry);
         SettingsRegistryMergeUtils::MergeSettingsToRegistry_O3deUserRegistry(*m_settingsRegistry, AZ_TRAIT_OS_PLATFORM_CODENAME, {});

Code/Framework/AzCore/AzCore/Settings/SettingsRegistryMergeUtils.cpp

@@ -132,23 +132,14 @@ namespace AZ::Internal
 
     AZ::IO::FixedMaxPath ScanUpRootLocator(AZStd::string_view rootFileToLocate)
     {
-
-        AZStd::fixed_string<AZ::IO::MaxPathLength> executableDir;
-        if (AZ::Utils::GetExecutableDirectory(executableDir.data(), executableDir.capacity()) == Utils::ExecutablePathResult::Success)
-        {
-            // Update the size value of the executable directory fixed string to correctly be the length of the null-terminated string
-            // stored within it
-            executableDir.resize_no_construct(AZStd::char_traits<char>::length(executableDir.data()));
-        }
-
-        AZ::IO::FixedMaxPath engineRootCandidate{ executableDir };
+        AZ::IO::FixedMaxPath rootCandidate{ AZ::Utils::GetExecutableDirectory() };
 
         bool rootPathVisited = false;
         do
         {
-            if (AZ::IO::SystemFile::Exists((engineRootCandidate / rootFileToLocate).c_str()))
+            if (AZ::IO::SystemFile::Exists((rootCandidate / rootFileToLocate).c_str()))
             {
-                return engineRootCandidate;
+                return rootCandidate;
             }
 
             // Note for posix filesystems the parent directory of '/' is '/' and for windows
@@ -156,38 +147,69 @@ namespace AZ::Internal
 
             // Validate that the parent directory isn't itself, that would imply
             // that it is the filesystem root path
-            AZ::IO::PathView parentPath = engineRootCandidate.ParentPath();
-            rootPathVisited = (engineRootCandidate == parentPath);
+            AZ::IO::PathView parentPath = rootCandidate.ParentPath();
+            rootPathVisited = (rootCandidate == parentPath);
             // Recurse upwards one directory
-            engineRootCandidate = AZStd::move(parentPath);
+            rootCandidate = AZStd::move(parentPath);
 
         } while (!rootPathVisited);
 
         return {};
     }
 
+    void InjectSettingToCommandLineFront(AZ::SettingsRegistryInterface& settingsRegistry,
+        AZStd::string_view path, AZStd::string_view value)
+    {
+        AZ::CommandLine commandLine;
+        AZ::SettingsRegistryMergeUtils::GetCommandLineFromRegistry(settingsRegistry, commandLine);
+        AZ::CommandLine::ParamContainer paramContainer;
+        commandLine.Dump(paramContainer);
+
+        auto projectPathOverride = AZStd::string::format(R"(--regset="%.*s=%.*s")",
+            aznumeric_cast<int>(path.size()), path.data(), aznumeric_cast<int>(value.size()), value.data());
+        paramContainer.emplace(paramContainer.begin(), AZStd::move(projectPathOverride));
+        commandLine.Parse(paramContainer);
+        AZ::SettingsRegistryMergeUtils::StoreCommandLineToRegistry(settingsRegistry, commandLine);
+    }
 } // namespace AZ::Internal
 
 namespace AZ::SettingsRegistryMergeUtils
 {
+    constexpr AZStd::string_view InternalScanUpEngineRootKey{ "/O3DE/Settings/Internal/engine_root_scan_up_path" };
+    constexpr AZStd::string_view InternalScanUpProjectRootKey{ "/O3DE/Settings/Internal/project_root_scan_up_path" };
+
     AZ::IO::FixedMaxPath FindEngineRoot(SettingsRegistryInterface& settingsRegistry)
     {
         AZ::IO::FixedMaxPath engineRoot;
-
         // This is the 'external' engine root key, as in passed from command-line or .setreg files.
         auto engineRootKey = SettingsRegistryInterface::FixedValueString::format("%s/engine_path", BootstrapSettingsRootKey);
+
+        // Step 1 Run the scan upwards logic once to find the location of the engine.json if it exist
+        // Once this step is run the {InternalScanUpEngineRootKey} is set in the Settings Registry
+        // to have this scan logic only run once InternalScanUpEngineRootKey the supplied registry
+        if (settingsRegistry.GetType(InternalScanUpEngineRootKey) == SettingsRegistryInterface::Type::NoType)
+        {
+            // We can scan up from exe directory to find engine.json, use that for engine root if it exists.
+            engineRoot = Internal::ScanUpRootLocator("engine.json");
+            // Set the {InternalScanUpEngineRootKey} to make sure this code path isn't called again for this settings registry
+            settingsRegistry.Set(InternalScanUpEngineRootKey, engineRoot.Native());
+            if (!engineRoot.empty())
+            {
+                settingsRegistry.Set(engineRootKey, engineRoot.Native());
+                // Inject the engine root into the front of the command line settings
+                Internal::InjectSettingToCommandLineFront(settingsRegistry, engineRootKey, engineRoot.Native());
+                return engineRoot;
+            }
+        }
+
+        // Step 2 check if the engine_path key has been supplied
         if (settingsRegistry.Get(engineRoot.Native(), engineRootKey); !engineRoot.empty())
         {
             return engineRoot;
         }
 
-        // We can scan up from exe directory to find engine.json, use that for engine root if it exists.
-        if (engineRoot = Internal::ScanUpRootLocator("engine.json"); !engineRoot.empty())
-        {
-            settingsRegistry.Set(engineRootKey, engineRoot.c_str());
-            return engineRoot;
-        }
-
+        // Step 3 locate the project root and attempt to find the engine root using the registered engine
+        // for the project in the project.json file
         AZ::IO::FixedMaxPath projectRoot = FindProjectRoot(settingsRegistry);
         if (projectRoot.empty())
         {
@@ -207,16 +229,30 @@ namespace AZ::SettingsRegistryMergeUtils
     AZ::IO::FixedMaxPath FindProjectRoot(SettingsRegistryInterface& settingsRegistry)
     {
         AZ::IO::FixedMaxPath projectRoot;
-        // This is the 'external' project root key, as in passed from command-line or .setreg files.
-        auto projectRootKey = SettingsRegistryInterface::FixedValueString::format("%s/project_path", BootstrapSettingsRootKey);
-        if (settingsRegistry.Get(projectRoot.Native(), projectRootKey))
+        const auto projectRootKey = SettingsRegistryInterface::FixedValueString::format("%s/project_path", BootstrapSettingsRootKey);
+
+        // Step 1 Run the scan upwards logic once to find the location of the project.json if it exist
+        // Once this step is run the {InternalScanUpProjectRootKey} is set in the Settings Registry
+        // to have this scan logic only run once for the supplied registry
+        // SettingsRegistryInterface::GetType is used to check if a key is set
+        if (settingsRegistry.GetType(InternalScanUpProjectRootKey) == SettingsRegistryInterface::Type::NoType)
         {
-            return projectRoot;
+            projectRoot = Internal::ScanUpRootLocator("project.json");
+            // Set the {InternalScanUpProjectRootKey} to make sure this code path isn't called again for this settings registry
+            settingsRegistry.Set(InternalScanUpProjectRootKey, projectRoot.Native());
+            if (!projectRoot.empty())
+            {
+                settingsRegistry.Set(projectRootKey, projectRoot.c_str());
+                // Inject the project root into the front of the command line settings
+                Internal::InjectSettingToCommandLineFront(settingsRegistry, projectRootKey, projectRoot.Native());
+                return projectRoot;
+            }
         }
 
-        if (projectRoot = Internal::ScanUpRootLocator("project.json"); !projectRoot.empty())
+        // Step 2 Check the project-path key
+        // This is the project path root key, as in passed from command-line or .setreg files.
+        if (settingsRegistry.Get(projectRoot.Native(), projectRootKey))
         {
-            settingsRegistry.Set(projectRootKey, projectRoot.c_str());
             return projectRoot;
         }
 
@@ -463,18 +499,6 @@ namespace AZ::SettingsRegistryMergeUtils
     void MergeSettingsToRegistry_Bootstrap(SettingsRegistryInterface& registry)
     {
         ConfigParserSettings parserSettings;
-        parserSettings.m_commentPrefixFunc = [](AZStd::string_view line) -> AZStd::string_view
-        {
-            constexpr AZStd::string_view commentPrefixes[]{ "--", ";","#" };
-            for (AZStd::string_view commentPrefix : commentPrefixes)
-            {
-                if (size_t commentOffset = line.find(commentPrefix); commentOffset != AZStd::string_view::npos)
-                {
-                    return line.substr(0, commentOffset);
-                }
-            }
-            return line;
-        };
         parserSettings.m_registryRootPointerPath = BootstrapSettingsRootKey;
         MergeSettingsToRegistry_ConfigFile(registry, "bootstrap.cfg", parserSettings);
     }
@@ -807,6 +831,11 @@ namespace AZ::SettingsRegistryMergeUtils
             ++argumentIndex;
             commandLinePath.resize(commandLineRootSize);
         }
+
+        // This key is used allow Notification Handlers to know when the command line has been updated within the
+        // registry. The value itself is meaningless. The JSON path of {CommandLineValueChangedKey}
+        // being passed to the Notification Event Handler indicates that the command line has be updated
+        registry.Set(CommandLineValueChangedKey, true);
     }
 
     bool GetCommandLineFromRegistry(SettingsRegistryInterface& registry, AZ::CommandLine& commandLine)
@@ -823,10 +852,16 @@ namespace AZ::SettingsRegistryMergeUtils
                 }
                 else if (valueName == "Value" && !value.empty())
                 {
-                    m_arguments.push_back(value);
+                    // Make sure value types are in quotes in case they start with a command option prefix
+                    m_arguments.push_back(QuoteArgument(value));
                 }
             }
 
+            AZStd::string QuoteArgument(AZStd::string_view arg)
+            {
+                return !arg.empty() ? AZStd::string::format(R"("%.*s")", aznumeric_cast<int>(arg.size()), arg.data()) : AZStd::string{ arg };
+            }
+
             // The first parameter is skipped by the ComamndLine::Parse function so initialize
             // the container with one empty element
             AZ::CommandLine::ParamContainer m_arguments{ 1 };

Code/Framework/AzCore/AzCore/Settings/SettingsRegistryMergeUtils.h

@@ -57,6 +57,9 @@ namespace AZ::SettingsRegistryMergeUtils
 
     //! Root key for where command line are stored at within the settings registry
     inline static constexpr char CommandLineRootKey[] = "/Amazon/AzCore/Runtime/CommandLine";
+    //! Key set to trigger a notification that the CommandLine has been stored within the settings registry
+    //! The value of the key has no meaning. Notification Handlers only need to check if the key was supplied
+    inline static constexpr char CommandLineValueChangedKey[] = "/Amazon/AzCore/Runtime/CommandLineChanged";
 
     //! Root key where raw project settings (project.json) file is merged to settings registry
     inline static constexpr char ProjectSettingsRootKey[] = "/Amazon/Project/Settings";
@@ -74,6 +77,20 @@ namespace AZ::SettingsRegistryMergeUtils
     //! If it's still not found, attempt to find the project (by similar means) then reconcile the
     //! engine root by inspecting project.json and the engine manifest file.
     AZ::IO::FixedMaxPath FindEngineRoot(SettingsRegistryInterface& settingsRegistry);
+
+    //! The algorithm that is used to find the project root is as follows
+    //! 1. The first time this function is it performs a upward scan for a project.json file from
+    //! the executable directory and if found stores that path to an internal key.
+    //! In the same step it injects the path into the front of list of command line parameters
+    //! using the --regset="{BootstrapSettingsRootKey}/project_path=<path>" value
+    //! 2. Next the "{BootstrapSettingsRootKey}/project_path" is checked to see if it has a project path set
+    //!
+    //! The order in which the project path settings are overridden proceeds in the following order
+    //! 1. project_path set in the <engine-root>/bootstrap.cfg file
+    //! 2. project_path set in a *.setreg/*.setregpatch file
+    //! 3. project_path found by scanning upwards from the executable directory to the project.json path
+    //! 4. project_path set on the Command line via either --regset="{BootstrapSettingsRootKey}/project_path=<path>"
+    //!    or --project_path=<path>
     AZ::IO::FixedMaxPath FindProjectRoot(SettingsRegistryInterface& settingsRegistry);
 
     //! Query the specializations that will be used when loading the Settings Registry.