rust: Stylized name builder

bindings/rust/evmc-bind/src/lib.rs

@@ -2,12 +2,17 @@ extern crate proc_macro;
 
 use heck::ShoutySnakeCase;
 use heck::SnakeCase;
+use heck::TitleCase;
 use proc_macro::TokenStream;
 use syn::parse_macro_input;
 use syn::ItemStruct;
+use syn::Lit;
+use syn::Meta;
+use syn::MetaList;
+use syn::NestedMeta;
 
 #[proc_macro_attribute]
-pub fn evmc_raw(_attr: TokenStream, item: TokenStream) -> TokenStream {
+pub fn evmc_raw(args: TokenStream, item: TokenStream) -> TokenStream {
     // First, try to parse the input token stream into an AST node representing a struct
     // declaration.
     let input: ItemStruct = parse_macro_input!(item as ItemStruct);
@@ -17,9 +22,51 @@ pub fn evmc_raw(_attr: TokenStream, item: TokenStream) -> TokenStream {
 
     // Get the name in shouty snake case for the statically defined VM data.
     let vm_name_allcaps: String = vm_type_name.to_shouty_snake_case();
-    
+
     // Get the name in snake case and strip the underscores for the symbol name.
-    let vm_name_lowercase: String = vm_type_name.to_snake_case().chars().filter(|c| *c != '_').collect();
+    let vm_name_lowercase: String = vm_type_name
+        .to_snake_case()
+        .chars()
+        .filter(|c| *c != '_')
+        .collect();
+
+    // The stylized VM name can optionally be included as an argument for the attribute. If it is
+    // not provided, the stylized name defaults to the name of the VM struct in title case.
+    let vm_name_stylized: String = if !args.is_empty() {
+        let meta = parse_macro_input!(args as MetaList);
+
+        // If we have more than one argument, throw a compile error. Otherwise, extract the item
+        // and try to form a valid stylized name from it.
+        if meta.nested.len() != 1 {
+            panic!("More than one meta-item supplied to evmc_raw")
+        } else {
+            match meta
+                .nested
+                .first()
+                .expect("Meta-item list missing a first element.")
+                .into_value()
+            {
+                NestedMeta::Meta(m) => {
+                    // Try to form a string from the identifier if a meta-item was supplied.
+                    if let Meta::Word(id) = m {
+                        id.to_string()
+                    } else {
+                        panic!("Meta-item passed to evmc_raw is not a valid identifier")
+                    }
+                }
+                NestedMeta::Literal(l) => {
+                    // Try to extract a valid UTF-8 string if a literal was supplied.
+                    if let Lit::Str(s) = l {
+                        s.value()
+                    } else {
+                        panic!("Literal passed to evmc_raw is not a valid UTF-8 string literal")
+                    }
+                }
+            }
+        }
+    } else {
+        vm_type_name.to_title_case()
+    };
 
     // struct declaration transformation
     // capabilities