builder through test 5, working on test 6

builder/Cargo.toml

@@ -16,4 +16,5 @@ path = "tests/progress.rs"
 trybuild = { version = "1.0.49", features = ["diff"] }
 
 [dependencies]
-# TODO
+quote = "1.0.36"
+syn = { version = "2.0.72", features = ["extra-traits", "printing"] }

builder/src/lib.rs

@@ -1,8 +1,97 @@
+#![allow(unused)]
+
 use proc_macro::TokenStream;
+use quote::{format_ident, quote};
+use syn;
 
 #[proc_macro_derive(Builder)]
-pub fn derive(input: TokenStream) -> TokenStream {
-    let _ = input;
+pub fn derive(item: TokenStream) -> TokenStream {
+    let input = syn::parse_macro_input!(item as syn::DeriveInput);
+    let syn::DeriveInput {
+        ident,
+        data: syn::Data::Struct(syn::DataStruct { fields, .. }),
+        ..
+    } = input
+    else {
+        todo!()
+    };
+    let builder_ident = format_ident!("{}Builder", ident);
+
+    let syn::Fields::Named(syn::FieldsNamed { named, .. }) = fields else {
+        todo!()
+    };
+    let fields = named.iter();
+
+    let struct_impl = quote! {
+        impl #ident {
+            pub fn builder() -> #builder_ident {
+                #builder_ident {
+                    ..Default::default()
+                }
+            }
+        }
+    };
+
+    let option_fields = fields.clone().map(|f| {
+        let name = &f.ident;
+        let ty = &f.ty;
+        quote! { #name: std::option::Option<#ty> }
+    });
+    let builder_def = quote! {
+        #[derive(Default)]
+        pub struct #builder_ident {
+            #( #option_fields ),*
+        }
+    };
+
+    let field_methods = fields.clone().map(|f| {
+        let name = &f.ident;
+        let ty = &f.ty;
+        let optional_fields;
+        if let syn::Type::Path(syn::TypePath {
+            path: syn::Path { segments, .. },
+            ..
+        }) = ty
+        {
+            optional_fields = segments.iter().filter_map(|seg| {
+                let syn::PathSegment { ident, arguments } = seg;
+                if ident == &format_ident!("Option") {
+                    return None;
+                }
+                Some(seg)
+            })
+        }
+        quote! {
+            pub fn #name(&mut self, #name: #ty) -> &mut Self {
+                self.#name = Some(#name);
+                self
+            }
+        }
+    });
+    let built_fields = fields.clone().map(|f| {
+        let name = &f.ident;
+        let ty = &f.ty;
+        let err_msg = format!("{} missing", name.as_ref().unwrap());
+        quote! {
+            #name: self.#name.clone().ok_or(#err_msg)?
+        }
+    });
+
+    let builder_impl = quote! {
+        impl #builder_ident {
+            #( #field_methods )*
+            fn build(&self) -> Result<#ident, Box<dyn std::error::Error>> {
+                Ok(#ident {
+                    #( #built_fields ),*
+                })
+            }
+        }
+    };
 
-    unimplemented!()
+    quote! {
+            #struct_impl
+            #builder_def
+            #builder_impl
+    }
+    .into()
 }

builder/tests/progress.rs

@@ -1,11 +1,11 @@
 #[test]
 fn tests() {
     let t = trybuild::TestCases::new();
-    //t.pass("tests/01-parse.rs");
-    //t.pass("tests/02-create-builder.rs");
-    //t.pass("tests/03-call-setters.rs");
-    //t.pass("tests/04-call-build.rs");
-    //t.pass("tests/05-method-chaining.rs");
+    t.pass("tests/01-parse.rs");
+    t.pass("tests/02-create-builder.rs");
+    t.pass("tests/03-call-setters.rs");
+    t.pass("tests/04-call-build.rs");
+    t.pass("tests/05-method-chaining.rs");
     //t.pass("tests/06-optional-field.rs");
     //t.pass("tests/07-repeated-field.rs");
     //t.compile_fail("tests/08-unrecognized-attribute.rs");