Add ExpandAttribute handler (#1684)

**Stack**:
- #1686
- #1685
- #1684 ⬅


⚠️ *Part of a stack created by [spr](https://github.com/ejoffe/spr). Do
not merge manually using the UI - doing so may have unexpected results.*

scarb/src/ops/proc_macro_server/methods/expand_attribute.rs

@@ -0,0 +1,29 @@
+use std::sync::Arc;
+
+use anyhow::Result;
+use scarb_proc_macro_server_types::methods::{expand::ExpandAttribute, ProcMacroResult};
+
+use super::Handler;
+use crate::compiler::plugin::proc_macro::{ExpansionKind, ProcMacroHost};
+
+impl Handler for ExpandAttribute {
+    fn handle(proc_macro_host: Arc<ProcMacroHost>, params: Self::Params) -> Result<Self::Response> {
+        let instance = proc_macro_host
+            .macros()
+            .iter()
+            .find(|e| {
+                e.get_expansions()
+                    .iter()
+                    .filter(|expansion| expansion.kind == ExpansionKind::Attr)
+                    .any(|expansion| expansion.name == params.attr)
+            })
+            .unwrap();
+
+        let result = instance.generate_code(params.attr.into(), params.args, params.item);
+
+        Ok(ProcMacroResult {
+            token_stream: result.token_stream,
+            diagnostics: result.diagnostics,
+        })
+    }
+}

scarb/src/ops/proc_macro_server/methods/mod.rs

@@ -6,6 +6,7 @@ use scarb_proc_macro_server_types::methods::Method;
 use crate::compiler::plugin::proc_macro::ProcMacroHost;
 
 pub mod defined_macros;
+pub mod expand_attribute;
 
 pub trait Handler: Method {
     fn handle(proc_macro_host: Arc<ProcMacroHost>, params: Self::Params) -> Result<Self::Response>;

scarb/src/ops/proc_macro_server/mod.rs

@@ -8,6 +8,7 @@ use crossbeam_channel::{Receiver, Sender};
 use methods::Handler;
 use scarb_proc_macro_server_types::jsonrpc::{ResponseError, RpcRequest, RpcResponse};
 use scarb_proc_macro_server_types::methods::defined_macros::DefinedMacros;
+use scarb_proc_macro_server_types::methods::expand::ExpandAttribute;
 use scarb_proc_macro_server_types::methods::Method;
 use serde_json::Value;
 
@@ -70,6 +71,9 @@ fn handle_requests(
 fn route_request(proc_macros: Arc<ProcMacroHost>, request: RpcRequest) -> Result<Value> {
     match request.method.as_str() {
         DefinedMacros::METHOD => run_handler::<DefinedMacros>(proc_macros.clone(), request.value),
+        ExpandAttribute::METHOD => {
+            run_handler::<ExpandAttribute>(proc_macros.clone(), request.value)
+        }
         _ => Err(anyhow!("method not found")),
     }
 }

scarb/tests/proc_macro_server.rs

@@ -1,7 +1,10 @@
 use assert_fs::prelude::PathChild;
 use assert_fs::TempDir;
+use cairo_lang_macro::TokenStream;
 use scarb_proc_macro_server_types::methods::defined_macros::DefinedMacros;
 use scarb_proc_macro_server_types::methods::defined_macros::DefinedMacrosParams;
+use scarb_proc_macro_server_types::methods::expand::ExpandAttribute;
+use scarb_proc_macro_server_types::methods::expand::ExpandAttributeParams;
 use scarb_test_support::cairo_plugin_project_builder::CairoPluginProjectBuilder;
 use scarb_test_support::proc_macro_server::ProcMacroClient;
 use scarb_test_support::proc_macro_server::SIMPLE_MACROS;
@@ -36,3 +39,52 @@ fn defined_macros() {
     assert_eq!(response.inline_macros, vec!["inline_some".to_string()]);
     assert_eq!(response.executables, vec!["some_executable".to_string()]);
 }
+
+#[test]
+fn expand_attribute() {
+    let t = TempDir::new().unwrap();
+    let plugin_package = t.child("some");
+
+    let rename_to_very_new_name = r##"
+        #[attribute_macro]
+        pub fn rename_to_very_new_name(_attr: TokenStream, token_stream: TokenStream) -> ProcMacroResult {{
+            let re = regex::Regex::new(r#"fn (\w+)\(.*\)\{.*\}"#).unwrap();
+            let input = token_stream.to_string();
+            let name = re.captures(&input).unwrap().get(1).unwrap().as_str();
+
+            let output = input.replace(name, "very_new_name");
+
+            ProcMacroResult::new(TokenStream::new(output))
+        }}
+    "##;
+
+    CairoPluginProjectBuilder::default()
+        .lib_rs(format!("{SIMPLE_MACROS}\n{rename_to_very_new_name}"))
+        .add_dep(r#"regex = "1.11.1""#)
+        .build(&plugin_package);
+
+    let project = t.child("test_package");
+
+    ProjectBuilder::start()
+        .name("test_package")
+        .version("1.0.0")
+        .lib_cairo("")
+        .dep("some", plugin_package)
+        .build(&project);
+
+    let mut proc_macro_server = ProcMacroClient::new(&project);
+
+    let response = proc_macro_server
+        .request_and_wait::<ExpandAttribute>(ExpandAttributeParams {
+            attr: "rename_to_very_new_name".to_string(),
+            args: TokenStream::empty(),
+            item: TokenStream::new("fn some_test_fn(){}".to_string()),
+        })
+        .unwrap();
+
+    assert_eq!(response.diagnostics, vec![]);
+    assert_eq!(
+        response.token_stream,
+        TokenStream::new("fn very_new_name(){}".to_string())
+    );
+}