1 files changed, 209 insertions, 0 deletions
diff --git a/mingling_macros/src/func/pack_err.rs b/mingling_macros/src/func/pack_err.rs
new file mode 100644
index 0000000..36e550a
--- /dev/null
+++ b/mingling_macros/src/func/pack_err.rs
@@ -0,0 +1,209 @@
+use just_fmt::snake_case;
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{Ident, Token, Type, parse_macro_input};
+
+enum PackErrInput {
+    /// pack_err!(ErrorNotFound)
+    Simple { type_name: Ident },
+    /// pack_err!(ErrorNotDir = PathBuf)
+    Typed {
+        type_name: Ident,
+        inner_type: Box<Type>,
+    },
+}
+
+impl syn::parse::Parse for PackErrInput {
+    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
+        let type_name: Ident = input.parse()?;
+
+        if input.peek(Token![=]) {
+            input.parse::<Token![=]>()?;
+            let inner_type: Type = input.parse()?;
+            Ok(PackErrInput::Typed {
+                type_name,
+                inner_type: Box::new(inner_type),
+            })
+        } else {
+            Ok(PackErrInput::Simple { type_name })
+        }
+    }
+}
+
+#[allow(clippy::too_many_lines)]
+pub(crate) fn pack_err(input: TokenStream) -> TokenStream {
+    let parsed = parse_macro_input!(input as PackErrInput);
+
+    match parsed {
+        PackErrInput::Simple { type_name } => {
+            let name_str = type_name.to_string();
+            let snake_name = snake_case!(&name_str);
+
+            // Note: No longer derives Serialize under structural_renderer.
+            // Use pack_err_structural for structured output support.
+            let derive = quote! {
+                #[derive(::mingling::Grouped)]
+            };
+
+            let expanded = quote! {
+                #derive
+                pub struct #type_name {
+                    /// The snake_case name of this error, automatically set at compile time.
+                    pub name: String,
+                }
+
+                impl ::std::default::Default for #type_name {
+                    fn default() -> Self {
+                        Self {
+                            name: #snake_name.into(),
+                        }
+                    }
+                }
+
+                ::mingling::macros::register_type!(#type_name);
+            };
+
+            expanded.into()
+        }
+        PackErrInput::Typed {
+            type_name,
+            inner_type,
+        } => {
+            let name_str = type_name.to_string();
+            let snake_name = snake_case!(&name_str);
+
+            // Note: No longer derives Serialize under structural_renderer.
+            // Use pack_err_structural for structured output support.
+            let derive = quote! {
+                #[derive(::mingling::Grouped)]
+            };
+
+            let expanded = quote! {
+                #derive
+                pub struct #type_name {
+                    /// The snake_case name of this error, automatically set at compile time.
+                    pub name: String,
+                    /// Additional context info for this error.
+                    pub info: #inner_type,
+                }
+
+                impl #type_name {
+                    /// Creates a new error with the given info.
+                    /// The `name` field is automatically set to the snake_case of the struct name.
+                    pub fn new(info: #inner_type) -> Self {
+                        Self {
+                            name: #snake_name.into(),
+                            info,
+                        }
+                    }
+                }
+
+                ::mingling::macros::register_type!(#type_name);
+            };
+
+            expanded.into()
+        }
+    }
+}
+
+/// `pack_err_structural!` — like `pack_err!` but also marks the type as
+/// supporting structured output via `StructuralData`.
+///
+/// # Syntax
+///
+/// ```rust,ignore
+/// pack_err_structural!(ErrorNotFound);
+/// pack_err_structural!(ErrorNotDir = PathBuf);
+/// ```
+///
+/// This is equivalent to:
+/// ```rust,ignore
+/// pack_err!(ErrorNotFound);
+/// impl ::mingling::__private::StructuralDataSealed for ErrorNotFound {}
+/// impl ::mingling::__private::StructuralData for ErrorNotFound {}
+/// ```
+#[cfg(feature = "structural_renderer")]
+pub(crate) fn pack_err_structural(input: TokenStream) -> TokenStream {
+    let parsed = parse_macro_input!(input as PackErrInput);
+
+    let type_name = match &parsed {
+        PackErrInput::Simple { type_name } => type_name.clone(),
+        PackErrInput::Typed { type_name, .. } => type_name.clone(),
+    };
+
+    // Register in STRUCTURED_TYPES
+    let type_name_str = type_name.to_string();
+    crate::get_global_set(&crate::STRUCTURED_TYPES)
+        .lock()
+        .unwrap()
+        .insert(type_name_str);
+
+    let structural_data = quote! {
+        impl ::mingling::__private::StructuralDataSealed for #type_name {}
+        impl ::mingling::__private::StructuralData for #type_name {}
+    };
+
+    // Generate the struct + impls (same as pack_err! but with Serialize derive + sealed)
+    match parsed {
+        PackErrInput::Simple { type_name } => {
+            let name_str = type_name.to_string();
+            let snake_name = snake_case!(&name_str);
+
+            let expanded = quote! {
+                #[derive(::mingling::Grouped, ::serde::Serialize)]
+                pub struct #type_name {
+                    /// The snake_case name of this error, automatically set at compile time.
+                    pub name: String,
+                }
+
+                impl ::std::default::Default for #type_name {
+                    fn default() -> Self {
+                        Self {
+                            name: #snake_name.into(),
+                        }
+                    }
+                }
+
+                ::mingling::macros::register_type!(#type_name);
+
+                #structural_data
+            };
+
+            expanded.into()
+        }
+        PackErrInput::Typed {
+            type_name,
+            inner_type,
+        } => {
+            let name_str = type_name.to_string();
+            let snake_name = snake_case!(&name_str);
+
+            let expanded = quote! {
+                #[derive(::mingling::Grouped, ::serde::Serialize)]
+                pub struct #type_name {
+                    /// The snake_case name of this error, automatically set at compile time.
+                    pub name: String,
+                    /// Additional context info for this error.
+                    pub info: #inner_type,
+                }
+
+                impl #type_name {
+                    /// Creates a new error with the given info.
+                    /// The `name` field is automatically set to the snake_case of the struct name.
+                    pub fn new(info: #inner_type) -> Self {
+                        Self {
+                            name: #snake_name.into(),
+                            info,
+                        }
+                    }
+                }
+
+                ::mingling::macros::register_type!(#type_name);
+
+                #structural_data
+            };
+
+            expanded.into()
+        }
+    }
+}