Support @export_storage attribute

godot-core/src/registry/property.rs

@@ -517,6 +517,7 @@ pub mod export_info_functions {
     // right side are the corresponding property hint. Godot is not always consistent between the two, such
     // as `export_multiline` being `PROPERTY_HINT_MULTILINE_TEXT`.
     default_export_funcs!(
+        export_storage => NONE, // Storage exports don't display in the editor.
         export_flags_2d_physics => LAYERS_2D_PHYSICS,
         export_flags_2d_render => LAYERS_2D_RENDER,
         export_flags_2d_navigation => LAYERS_2D_NAVIGATION,

godot-macros/src/class/data_models/field_export.rs

@@ -9,7 +9,7 @@ use proc_macro2::{Ident, Span, TokenStream};
 use quote::quote;
 use std::collections::{HashMap, HashSet};
 
-use crate::util::{KvParser, ListParser};
+use crate::util::{ident, KvParser, ListParser};
 use crate::ParseResult;
 
 pub struct FieldExport {
@@ -27,6 +27,10 @@ impl FieldExport {
     pub fn to_export_hint(&self) -> Option<TokenStream> {
         self.export_type.to_export_hint()
     }
+
+    pub fn to_export_usage(&self) -> Option<Ident> {
+        self.export_type.to_export_usage()
+    }
 }
 
 /// Store info from `#[export]` attribute.
@@ -40,6 +44,20 @@ pub enum ExportType {
     /// Can become other property hints, depends on context.
     Default,
 
+    /// ### GDScript annotations
+    /// - `@export_storage`
+    ///
+    /// ### Property hints
+    /// - `NONE`
+    ///
+    /// ### Property usage
+    /// - `STORAGE`
+    ///
+    /// This is used to indicate that the property should be exported
+    /// but should not be visible in the editor. Therefore, it does not
+    /// have a property hint, but uses the `STORAGE` property usage.
+    Storage,
+
     /// ### GDScript annotations
     /// - `@export_range`
     ///
@@ -150,6 +168,10 @@ impl ExportType {
     ///   becomes
     ///   `#[export(flags/enum = (elem1, elem2 = key2, ...))]`
     pub(crate) fn new_from_kv(parser: &mut KvParser) -> ParseResult<Self> {
+        if parser.handle_alone("storage")? {
+            return Self::new_storage();
+        }
+
         if let Some(list_parser) = parser.handle_list("range")? {
             return Self::new_range_list(list_parser);
         }
@@ -273,6 +295,10 @@ impl ExportType {
         Ok(Self::Default)
     }
 
+    fn new_storage() -> ParseResult<Self> {
+        Ok(Self::Storage)
+    }
+
     fn new_range_list(mut parser: ListParser) -> ParseResult<Self> {
         const FLAG_OPTIONS: [&str; 7] = [
             "or_greater",
@@ -404,6 +430,8 @@ impl ExportType {
         match self {
             Self::Default => None,
 
+            Self::Storage => quote_export_func! { export_storage() },
+
             Self::Range {
                 min,
                 max,
@@ -519,6 +547,13 @@ impl ExportType {
             Self::ColorNoAlpha => quote_export_func! { export_color_no_alpha() },
         }
     }
+
+    pub fn to_export_usage(&self) -> Option<Ident> {
+        match self {
+            Self::Storage => Some(ident("STORAGE")),
+            _ => None,
+        }
+    }
 }
 
 /// The dimension of a `@export_flags_{dimension}_{layer}` annotation.

godot-macros/src/class/data_models/property.rs

@@ -53,10 +53,17 @@ pub fn make_property_impl(class_name: &Ident, fields: &Fields) -> TokenStream {
 
         // Ensure we add a var if the user only provided a `#[export]`.
         let var = match (export, var) {
-            (Some(_), None) => Some(FieldVar {
-                usage_flags: UsageFlags::InferredExport,
-                ..Default::default()
-            }),
+            (Some(export), None) => {
+                let usage_flags = if let Some(usage) = export.to_export_usage() {
+                    UsageFlags::Custom(vec![usage])
+                } else {
+                    UsageFlags::InferredExport
+                };
+                Some(FieldVar {
+                    usage_flags,
+                    ..Default::default()
+                })
+            }
 
             (_, var) => var.clone(),
         };

godot-macros/src/lib.rs

@@ -243,7 +243,11 @@ use crate::util::{bail, ident, KvParser};
 ///     // @export
 ///     #[export]
 ///     float: f64,
-///     
+///
+///     // @export_storage
+///     #[export(storage)]
+///     hidden_string: GString,
+///
 ///     // @export_range(0.0, 10.0, or_greater)
 ///     #[export(range = (0.0, 10.0, or_greater))]
 ///     range_f64: f64,

itest/rust/build.rs

@@ -472,6 +472,9 @@ fn generate_property_template(inputs: &[Input]) -> PropertyTests {
         TokenStream::new()
     } else {
         quote! {
+            #[export(storage)]
+            export_storage: GString,
+
             #[export(file)]
             export_file_array: Array<GString>,
             #[export(file)]
@@ -597,6 +600,7 @@ fn generate_property_template(inputs: &[Input]) -> PropertyTests {
 
     // Only available in Godot 4.3+.
     let advanced_exports_4_3 = r#"
+@export_storage var export_storage: String
 @export_file var export_file_array: Array[String]
 @export_file var export_file_parray: PackedStringArray
 @export_file("*.txt") var export_file_wildcard_array: Array[String]

itest/rust/src/object_tests/property_template_test.rs

@@ -70,11 +70,15 @@ fn property_template_test(ctx: &TestContext) {
 
         let mut rust_usage = rust_prop.at("usage").to::<i64>();
 
-        // the GDSscript variables are script variables, and so have `PROPERTY_USAGE_SCRIPT_VARIABLE` set.
-        if rust_usage == PropertyUsageFlags::STORAGE.ord() as i64 {
-            // `PROPERTY_USAGE_SCRIPT_VARIABLE` does the same thing as `PROPERTY_USAGE_STORAGE` and so
-            // GDScript doesn't set both if it doesn't need to.
-            rust_usage = PropertyUsageFlags::SCRIPT_VARIABLE.ord() as i64
+        // The GDSscript variables are script variables, and so have `PROPERTY_USAGE_SCRIPT_VARIABLE` set.
+        // Before 4.3, `PROPERTY_USAGE_SCRIPT_VARIABLE` did the same thing as `PROPERTY_USAGE_STORAGE` and
+        // so GDScript didn't set both if it didn't need to.
+        if GdextBuild::before_api("4.3") {
+            if rust_usage == PropertyUsageFlags::STORAGE.ord() as i64 {
+                rust_usage = PropertyUsageFlags::SCRIPT_VARIABLE.ord() as i64
+            } else {
+                rust_usage |= PropertyUsageFlags::SCRIPT_VARIABLE.ord() as i64;
+            }
         } else {
             rust_usage |= PropertyUsageFlags::SCRIPT_VARIABLE.ord() as i64;
         }
@@ -102,11 +106,11 @@ fn property_template_test(ctx: &TestContext) {
             errors.push(format!(
                 "mismatch in property {name}:\n  GDScript: {gdscript_prop:?}\n  Rust:     {rust_prop:?}"
             ));
-        } /*else {
-              println!("matching property {name}\n  GDScript: {gdscript_prop:?}\n  Rust:     {rust_prop:?}");
-          }*/
+        }
     }
 
+    rust_properties.free();
+
     assert!(
         properties.is_empty(),
         "not all properties were matched, missing: {properties:?}"
@@ -118,6 +122,4 @@ fn property_template_test(ctx: &TestContext) {
         errors.len(),
         errors.join("\n")
     );
-
-    rust_properties.free();
 }