feat(serde): make serde optional default

Cargo.toml

@@ -4,7 +4,7 @@ members = ["filecaster", "filecaster-derive"]
 
 [workspace.dependencies]
 serde = { version = "1.0", features = ["derive"] }
-merge = "0.2.0"
+merge = "0.2"
 # dev-dependencies
 claims = "0.8"
 serde_json = "1.0"

filecaster-derive/Cargo.toml

@@ -7,7 +7,8 @@ edition = "2024"
 proc-macro = true
 
 [features]
-default = []
+default = ["serde"]
+serde = ["dep:serde"]
 merge = ["dep:merge"]
 
 [dependencies]
@@ -15,7 +16,7 @@ proc-macro2 = "1.0"
 quote = "1.0"
 proc-macro-error2 = "2.0"
 syn = { version = "2.0", features = ["extra-traits", "parsing"] }
-serde.workspace = true
+serde = { workspace = true, optional = true }
 merge = { workspace = true, optional = true }
 
 [dev-dependencies]

filecaster-derive/src/from_file.rs

@@ -1,5 +1,3 @@
-use std::path::PathBuf;
-
 use proc_macro2::TokenStream;
 use quote::{format_ident, quote};
 use syn::{
@@ -72,23 +70,6 @@ fn extract_named_fields(input: &DeriveInput) -> Result<&FieldsNamed> {
     }
 }
 
-/// Nested-struct detection
-fn is_from_file_struct(ty: &Type) -> bool {
-    if let Type::Path(TypePath { qself: None, path }) = ty {
-        return path.segments.len() == 1;
-    }
-    false
-}
-
-/// Extract the last identifier from a [`TypePath`].
-fn last_path_ident(ty: &Type) -> Result<String> {
-    if let Type::Path(TypePath { qself: None, path }) = ty {
-        return Ok(path.segments.last().unwrap().ident.to_string());
-    }
-
-    Err(Error::new_spanned(ty, "expected a plain struct name"))
-}
-
 /// Build the shadow field + assignment for one original field
 fn build_file_field(field: &Field) -> Result<(TokenStream, TokenStream, Option<TokenStream>)> {
     let ident = field
@@ -159,14 +140,10 @@ fn build_where_clause(
 
 /// Derive clause for the shadow struct
 fn build_derive_clause() -> TokenStream {
-    if WITH_MERGE {
-        return quote! {
-            #[derive(Debug, Clone, Default, serde::Deserialize, serde::Serialize, merge::Merge)]
-        };
-    }
-
     quote! {
-        #[derive(Debug, Clone, Default, serde::Deserialize, serde::Serialize)]
+        #[derive(Debug, Clone, Default)]
+        #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+        #[cfg_attr(feature = "merge", derive(merge::Merge))]
     }
 }
 
@@ -332,21 +309,6 @@ mod tests {
         assert_eq!(preds, vec!["Z : Eq".to_string()]);
     }
 
-    #[test]
-    fn build_derive_clause_defaults() {
-        let derive_ts = build_derive_clause();
-        let s = derive_ts.to_string();
-        if WITH_MERGE {
-            assert!(s.contains(
-                "derive (Debug , Clone , Default , serde :: Deserialize , serde :: Serialize , merge :: Merge)"
-            ));
-        } else {
-            assert!(s.contains(
-                "derive (Debug , Clone , Default , serde :: Deserialize , serde :: Serialize)"
-            ));
-        }
-    }
-
     #[test]
     fn add_trait_bouds_appends_default() {
         let gens: Generics = parse_quote!(<T, U>);

filecaster/Cargo.toml

@@ -14,13 +14,14 @@ exclude = ["/.github", "/.gitignore", "/tests", "*.png", "*.md"]
 readme = "README.md"
 
 [features]
-default = ["derive"]
+default = ["serde", "derive"]
 derive = ["dep:filecaster-derive"]
+serde = ["dep:serde", "filecaster-derive/serde"]
 merge = ["dep:merge", "filecaster-derive/merge"]
 
 [dependencies]
 filecaster-derive = { path = "../filecaster-derive", optional = true }
-serde.workspace = true
+serde = { workspace = true, optional = true }
 merge = { workspace = true, optional = true }
 
 [dev-dependencies]

filecaster/src/lib.rs

@@ -1,4 +1,5 @@
 pub use filecaster_derive::FromFile;
+#[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
 
 /// Marker for types that can be built from an `Option<Shadow>` produced by the macro.
@@ -6,9 +7,13 @@ pub trait FromFile: Sized {
     fn from_file(file: Option<Self::Shadow>) -> Self;
 
     /// Associated shadow type generated by the macro.
+    #[cfg(feature = "serde")]
     type Shadow: Default + Serialize + for<'de> Deserialize<'de>;
+    #[cfg(not(feature = "serde"))]
+    type Shadow: Default;
 }
 
+#[cfg(feature = "serde")]
 impl<T> FromFile for T
 where
     T: Default + Serialize + for<'de> Deserialize<'de>,
@@ -18,3 +23,14 @@ where
         file.unwrap_or_default()
     }
 }
+
+#[cfg(not(feature = "serde"))]
+impl<T> FromFile for T
+where
+    T: Default,
+{
+    type Shadow = T;
+    fn from_file(file: Option<Self::Shadow>) -> Self {
+        file.unwrap_or_default()
+    }
+}