Add derive macro under feature

Cargo.lock

@@ -4,4 +4,104 @@ version = 3
 
 [[package]]
 name = "newt"
-version = "0.2.0"
+version = "0.3.1"
+dependencies = [
+ "newt-derive",
+ "newt-derive-core",
+]
+
+[[package]]
+name = "newt-derive"
+version = "0.1.0"
+dependencies = [
+ "newt-derive-core",
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.66",
+]
+
+[[package]]
+name = "newt-derive-core"
+version = "0.1.0"
+dependencies = [
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.66",
+]
+
+[[package]]
+name = "proc-macro-error"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da25490ff9892aab3fcf7c36f08cfb902dd3e71ca0f9f9517bea02a73a5ce38c"
+dependencies = [
+ "proc-macro-error-attr",
+ "proc-macro2",
+ "quote",
+ "syn 1.0.109",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro-error-attr"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1be40180e52ecc98ad80b184934baf3d0d29f979574e439af5a55274b35f869"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.85"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22244ce15aa966053a896d1accb3a6e68469b97c7f33f284b99f0d576879fc23"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.36"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0fa76aaf39101c457836aec0ce2316dbdc3ab723cdda1c6bd4e6ad4208acaca7"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "syn"
+version = "1.0.109"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "72b64191b275b66ffe2469e8af2c1cfe3bafa67b529ead792a6d0160888b4237"
+dependencies = [
+ "proc-macro2",
+ "unicode-ident",
+]
+
+[[package]]
+name = "syn"
+version = "2.0.66"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c42f3f41a2de00b01c0aaad383c5a45241efc8b2d1eda5661812fda5f3cdcff5"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3354b9ac3fae1ff6755cb6db53683adb661634f67557942dea4facebec0fee4b"
+
+[[package]]
+name = "version_check"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"

Cargo.toml

@@ -1,6 +1,23 @@
 [package]
 name = "newt"
-version = "0.3.0"
+version = "0.3.1"
 edition = "2021"
 
+[workspace]
+resolver = "2"
+members = ["derive", "derive/core"]
+
+[workspace.dependencies]
+proc-macro-error = "1.0"
+proc-macro2 = "1"
+syn = { version = "2", features = ["full"] }
+quote = "1"
+
 [dependencies]
+newt-derive = { path = "derive", optional = true }
+
+[dev-dependencies]
+newt-derive-core = { path = "derive/core" }
+
+[features]
+derive = ["dep:newt-derive"]

derive/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "newt-derive"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+proc-macro-error = { workspace = true }
+proc-macro2 = { workspace = true }
+syn = { workspace = true }
+quote = { workspace = true }
+
+newt-derive-core = { path = "./core" }
+
+[lib]
+proc-macro = true

derive/core/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "newt-derive-core"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+proc-macro-error = { workspace = true }
+proc-macro2 = { workspace = true }
+syn = { workspace = true }
+quote = { workspace = true }

derive/core/src/lib.rs

@@ -0,0 +1,83 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{Fields, ItemStruct};
+
+pub fn lookup_core(input: TokenStream) -> TokenStream {
+	let input: ItemStruct = match syn::parse2(input) {
+		Ok(i) => i,
+		Err(e) => return e.to_compile_error(),
+	};
+
+	let struct_name = input.ident;
+	let (ipl, ty, _) = input.generics.split_for_impl();
+
+	match input.fields {
+		Fields::Named(n) => {
+			let mut exprs = Vec::new();
+
+			for field in n.named {
+				let ident = field.ident.expect("named field should have name");
+				let ident_str = format!(r#"{ident}"#);
+				exprs.push(quote! {
+					#ident_str => Some(&self.#ident),
+				});
+			}
+
+			let output = quote! {
+				impl #ipl #struct_name #ty {
+					fn __lookup(&self, name: &str) -> Option<&dyn ::newt::Value> {
+						match name {
+							#(#exprs)*
+							_ => None,
+						}
+					}
+				}
+			};
+
+			output
+		},
+		Fields::Unnamed(_u) => {
+			todo!()
+		},
+		Fields::Unit => quote! {
+			todo!()
+		},
+	}
+}
+
+#[cfg(test)]
+mod test {
+	use quote::quote;
+
+	use crate::lookup_core;
+
+	macro_rules! go {
+		($in:expr, $exp:expr $(,)?) => {
+			assert_eq!(lookup_core($in).to_string(), $exp.to_string());
+		};
+	}
+
+	#[test]
+	pub fn named_fields_struct() {
+		go! {
+			quote! {
+				#[derive(Lookup)]
+				struct Test {
+					foo: String,
+					bar: String,
+				}
+			},
+			quote! {
+				impl Test {
+					fn __lookup(&self, name: &str) -> Option<&dyn ::newt::Value> {
+						match name {
+							"foo" => Some(&self.foo),
+							"bar" => Some(&self.bar),
+							_ => None,
+						}
+					}
+				}
+			},
+		};
+	}
+}

derive/src/lib.rs

@@ -0,0 +1,9 @@
+use newt_derive_core::lookup_core;
+use proc_macro::TokenStream;
+use proc_macro_error::proc_macro_error;
+
+#[proc_macro_error]
+#[proc_macro_derive(Lookup)]
+pub fn lookup(input: TokenStream) -> TokenStream {
+	lookup_core(input.into()).into()
+}

src/lib.rs

@@ -478,3 +478,6 @@ macro_rules! values {
 		]
 	}}
 }
+
+#[cfg(feature = "derive")]
+pub use newt_derive::Lookup;