Add macro for code metadata

Cargo.toml

@@ -59,12 +59,12 @@ git = "https://github.com/stellar/rs-stellar-xdr"
 rev = "bcf6f4c3a9dd32822a20af89880650a421d10e7f"
 default-features = false
 
-# [patch."https://github.com/stellar/rs-soroban-env"]
-# soroban-env-common = { path = "../rs-soroban-env/soroban-env-common" }
-# soroban-env-guest = { path = "../rs-soroban-env/soroban-env-guest" }
-# soroban-env-host = { path = "../rs-soroban-env/soroban-env-host/" }
-# [patch."https://github.com/stellar/rs-stellar-xdr"]
-# stellar-xdr = { path = "../rs-stellar-xdr/" }
+[patch."https://github.com/stellar/rs-soroban-env"]
+soroban-env-common = { path = "../rs-soroban-env/soroban-env-common" }
+soroban-env-guest = { path = "../rs-soroban-env/soroban-env-guest" }
+soroban-env-host = { path = "../rs-soroban-env/soroban-env-host/" }
+[patch."https://github.com/stellar/rs-stellar-xdr"]
+stellar-xdr = { path = "../rs-stellar-xdr/" }
 
 [profile.dev]
 overflow-checks = true

soroban-sdk-macros/src/lib.rs

@@ -23,7 +23,7 @@ use derive_struct_tuple::derive_type_struct_tuple;
 use darling::FromMeta;
 use proc_macro::TokenStream;
 use proc_macro2::{Literal, Span, TokenStream as TokenStream2};
-use quote::quote;
+use quote::{format_ident, quote};
 use sha2::{Digest, Sha256};
 use std::fs;
 use syn::{
@@ -35,6 +35,8 @@ use self::derive_client::ClientItem;
 
 use soroban_spec::gen::rust::{generate_from_wasm, GenerateFromFileError};
 
+use stellar_xdr::{ScMetaEntry, ScMetaV0, StringM, WriteXdr};
+
 fn default_crate_path() -> Path {
     parse_str("soroban_sdk").unwrap()
 }
@@ -95,6 +97,74 @@ pub fn contractimpl(_metadata: TokenStream, input: TokenStream) -> TokenStream {
     }
 }
 
+#[derive(Debug, FromMeta)]
+struct MetadataArgs {
+    key: String,
+    val: String,
+}
+
+#[proc_macro]
+pub fn contractmeta(metadata: TokenStream) -> TokenStream {
+    let args = parse_macro_input!(metadata as AttributeArgs);
+    let args = match MetadataArgs::from_list(&args) {
+        Ok(v) => v,
+        Err(e) => return e.write_errors().into(),
+    };
+
+    let gen = {
+        let key: StringM<10> = match args.key.clone().try_into() {
+            Ok(k) => k,
+            Err(e) => {
+                return Error::new(Span::call_site(), e.to_string())
+                    .into_compile_error()
+                    .into()
+            }
+        };
+
+        let val: StringM<256> = match args.val.try_into() {
+            Ok(k) => k,
+            Err(e) => {
+                return Error::new(Span::call_site(), e.to_string())
+                    .into_compile_error()
+                    .into()
+            }
+        };
+
+        let meta_v0 = ScMetaV0 { key, val };
+        let meta_entry = ScMetaEntry::ScMetaV0(meta_v0);
+        let metadata_xdr: Vec<u8> = match meta_entry.to_xdr() {
+            Ok(v) => v,
+            Err(e) => {
+                return Error::new(Span::call_site(), e.to_string())
+                    .into_compile_error()
+                    .into()
+            }
+        };
+
+        let metadata_xdr_lit = proc_macro2::Literal::byte_string(metadata_xdr.as_slice());
+        let metadata_xdr_len = metadata_xdr.len();
+
+        let ident = format_ident!(
+            "__CONTRACT_KEY_{}",
+            args.key
+                .as_bytes()
+                .iter()
+                .map(|b| format!("{b:02x}"))
+                .collect::<String>()
+        );
+        quote! {
+            #[doc(hidden)]
+            #[cfg_attr(target_family = "wasm", link_section = "contractmetav0")]
+            static #ident: [u8; #metadata_xdr_len] = *#metadata_xdr_lit;
+        }
+    };
+
+    quote! {
+        #gen
+    }
+    .into()
+}
+
 #[derive(Debug, FromMeta)]
 struct ContractTypeArgs {
     #[darling(default = "default_crate_path")]

soroban-sdk/src/lib.rs

@@ -298,6 +298,7 @@ pub use soroban_sdk_macros::contractimport;
 /// # fn main() { }
 /// ```
 pub use soroban_sdk_macros::contractimpl;
+pub use soroban_sdk_macros::contractmeta;
 
 /// Generates conversions from the struct/enum from/into a `RawVal`.
 ///