Add support for scene/resource customization in export plugins

EditorExportPlugin adds a set of callbacks to allow customizing scenes, resources or subresources in all files exported:
* Can take scene files, resource files and subresources in all of them.
* Uses a cache for the converted files if nothing changes, so this work only happens if a file is modified.
* Uses hashing to differentiate export configuration caches.
* Removed the previous conversion code to binary, as this one uses existing stuff.

This API is useful in several scenarios:
* Needed by the "server" export platform to get rid of textures, meshes, audio, etc.
* Needed by text to binary converters.
* Needed by eventual optimizations such as shader precompiling on export, mesh merging and optimization, etc.

This is a draft, feedback is very welcome.

core/io/config_file.cpp

@@ -32,6 +32,7 @@
 
 #include "core/io/file_access_encrypted.h"
 #include "core/os/keyboard.h"
+#include "core/string/string_builder.h"
 #include "core/variant/variant_parser.h"
 
 PackedStringArray ConfigFile::_get_sections() const {
@@ -130,6 +131,28 @@ void ConfigFile::erase_section_key(const String &p_section, const String &p_key)
 	}
 }
 
+String ConfigFile::encode_to_text() const {
+	StringBuilder sb;
+	bool first = true;
+	for (const KeyValue<String, HashMap<String, Variant>> &E : values) {
+		if (first) {
+			first = false;
+		} else {
+			sb.append("\n");
+		}
+		if (!E.key.is_empty()) {
+			sb.append("[" + E.key + "]\n\n");
+		}
+
+		for (const KeyValue<String, Variant> &F : E.value) {
+			String vstr;
+			VariantWriter::write_to_string(F.value, vstr);
+			sb.append(F.key.property_name_encode() + "=" + vstr + "\n");
+		}
+	}
+	return sb.as_string();
+}
+
 Error ConfigFile::save(const String &p_path) {
 	Error err;
 	Ref<FileAccess> file = FileAccess::open(p_path, FileAccess::WRITE, &err);
@@ -295,6 +318,7 @@ Error ConfigFile::_parse(const String &p_path, VariantParser::Stream *p_stream)
 void ConfigFile::clear() {
 	values.clear();
 }
+
 void ConfigFile::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_value", "section", "key", "value"), &ConfigFile::set_value);
 	ClassDB::bind_method(D_METHOD("get_value", "section", "key", "default"), &ConfigFile::get_value, DEFVAL(Variant()));
@@ -312,6 +336,8 @@ void ConfigFile::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("parse", "data"), &ConfigFile::parse);
 	ClassDB::bind_method(D_METHOD("save", "path"), &ConfigFile::save);
 
+	ClassDB::bind_method(D_METHOD("encode_to_text"), &ConfigFile::encode_to_text);
+
 	BIND_METHOD_ERR_RETURN_DOC("load", ERR_FILE_CANT_OPEN);
 
 	ClassDB::bind_method(D_METHOD("load_encrypted", "path", "key"), &ConfigFile::load_encrypted);

core/io/config_file.h

@@ -68,6 +68,8 @@ class ConfigFile : public RefCounted {
 	Error load(const String &p_path);
 	Error parse(const String &p_data);
 
+	String encode_to_text() const; // used by exporter
+
 	void clear();
 
 	Error load_encrypted(const String &p_path, const Vector<uint8_t> &p_key);

doc/classes/ConfigFile.xml

@@ -98,6 +98,12 @@
 				Removes the entire contents of the config.
 			</description>
 		</method>
+		<method name="encode_to_text" qualifiers="const">
+			<return type="String" />
+			<description>
+				Obtain the text version of this config file (the same text that would be written to a file).
+			</description>
+		</method>
 		<method name="erase_section">
 			<return type="void" />
 			<param index="0" name="section" type="String" />

doc/classes/EditorExportPlatform.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<class name="EditorExportPlatform" inherits="RefCounted" version="4.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
+	<brief_description>
+	</brief_description>
+	<description>
+	</description>
+	<tutorials>
+	</tutorials>
+</class>

doc/classes/EditorExportPlugin.xml

@@ -10,6 +10,51 @@
 	<tutorials>
 	</tutorials>
 	<methods>
+		<method name="_begin_customize_resources" qualifiers="virtual const">
+			<return type="bool" />
+			<param index="0" name="platform" type="EditorExportPlatform" />
+			<param index="1" name="features" type="PackedStringArray" />
+			<description>
+				Return true if this plugin will customize resources based on the platform and features used.
+			</description>
+		</method>
+		<method name="_begin_customize_scenes" qualifiers="virtual const">
+			<return type="bool" />
+			<param index="0" name="platform" type="EditorExportPlatform" />
+			<param index="1" name="features" type="PackedStringArray" />
+			<description>
+				Return true if this plugin will customize scenes based on the platform and features used.
+			</description>
+		</method>
+		<method name="_customize_resource" qualifiers="virtual">
+			<return type="Resource" />
+			<param index="0" name="resource" type="Resource" />
+			<param index="1" name="path" type="String" />
+			<description>
+				Customize a resource. If changes are made to it, return the same or a new resource. Otherwise, return [code]null[/code].
+				The [i]path[/i] argument is only used when customizing an actual file, otherwise this means that this resource is part of another one and it will be empty.
+			</description>
+		</method>
+		<method name="_customize_scene" qualifiers="virtual">
+			<return type="Node" />
+			<param index="0" name="scene" type="Node" />
+			<param index="1" name="path" type="String" />
+			<description>
+				Customize a scene. If changes are made to it, return the same or a new scene. Otherwise, return [code]null[/code]. If a new scene is returned, it is up to you to dispose of the old one.
+			</description>
+		</method>
+		<method name="_end_customize_resources" qualifiers="virtual">
+			<return type="void" />
+			<description>
+				This is called when the customization process for resources ends.
+			</description>
+		</method>
+		<method name="_end_customize_scenes" qualifiers="virtual">
+			<return type="void" />
+			<description>
+				This is called when the customization process for scenes ends.
+			</description>
+		</method>
 		<method name="_export_begin" qualifiers="virtual">
 			<return type="void" />
 			<param index="0" name="features" type="PackedStringArray" />
@@ -36,6 +81,18 @@
 				Calling [method skip] inside this callback will make the file not included in the export.
 			</description>
 		</method>
+		<method name="_get_customization_configuration_hash" qualifiers="virtual const">
+			<return type="int" />
+			<description>
+				Return a hash based on the configuration passed (for both scenes and resources). This helps keep separate caches for separate export configurations.
+			</description>
+		</method>
+		<method name="_get_name" qualifiers="virtual const">
+			<return type="String" />
+			<description>
+				Return the name identifier of this plugin (for future identification by the exporter).
+			</description>
+		</method>
 		<method name="add_file">
 			<return type="void" />
 			<param index="0" name="path" type="String" />

editor/editor_node.cpp

@@ -4107,6 +4107,7 @@ void EditorNode::register_editor_types() {
 	GDREGISTER_CLASS(EditorSyntaxHighlighter);
 	GDREGISTER_ABSTRACT_CLASS(EditorInterface);
 	GDREGISTER_CLASS(EditorExportPlugin);
+	GDREGISTER_ABSTRACT_CLASS(EditorExportPlatform);
 	GDREGISTER_CLASS(EditorResourceConversionPlugin);
 	GDREGISTER_CLASS(EditorSceneFormatImporter);
 	GDREGISTER_CLASS(EditorScenePostImportPlugin);
@@ -7418,11 +7419,6 @@ EditorNode::EditorNode() {
 	editor_plugins_force_over = memnew(EditorPluginList);
 	editor_plugins_force_input_forwarding = memnew(EditorPluginList);
 
-	Ref<EditorExportTextSceneToBinaryPlugin> export_text_to_binary_plugin;
-	export_text_to_binary_plugin.instantiate();
-
-	EditorExport::get_singleton()->add_export_plugin(export_text_to_binary_plugin);
-
 	Ref<GDExtensionExportPlugin> gdextension_export_plugin;
 	gdextension_export_plugin.instantiate();
 

editor/export/editor_export.cpp

@@ -351,6 +351,8 @@ EditorExport::EditorExport() {
 
 	singleton = this;
 	set_process(true);
+
+	GLOBAL_DEF("editor/export/convert_text_resources_to_binary", true);
 }
 
 EditorExport::~EditorExport() {