Add ExpandDerive handler (#1685)

**Stack**:
- #1686
- #1685 ⬅


⚠️ *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_derive.rs

@@ -0,0 +1,41 @@
+use std::sync::Arc;
+
+use anyhow::Result;
+use cairo_lang_macro::TokenStream;
+use convert_case::{Case, Casing};
+use scarb_proc_macro_server_types::methods::{expand::ExpandDerive, ProcMacroResult};
+
+use super::Handler;
+use crate::compiler::plugin::proc_macro::{Expansion, ExpansionKind, ProcMacroHost};
+
+impl Handler for ExpandDerive {
+    fn handle(proc_macro_host: Arc<ProcMacroHost>, params: Self::Params) -> Result<Self::Response> {
+        let mut derived_code = String::new();
+        let mut all_diagnostics = vec![];
+
+        for derive in params.derives {
+            let expansion = Expansion::new(derive.to_case(Case::Snake), ExpansionKind::Derive);
+            let instance = proc_macro_host
+                .macros()
+                .iter()
+                .find(|e| e.get_expansions().contains(&expansion))
+                .unwrap();
+
+            let result = instance.generate_code(
+                expansion.name.clone(),
+                TokenStream::empty(),
+                params.item.clone(),
+            );
+
+            // Register diagnostics.
+            all_diagnostics.extend(result.diagnostics);
+            // Add generated code.
+            derived_code.push_str(&result.token_stream.to_string());
+        }
+
+        Ok(ProcMacroResult {
+            token_stream: TokenStream::new(derived_code),
+            diagnostics: all_diagnostics,
+        })
+    }
+}

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

@@ -7,6 +7,7 @@ use crate::compiler::plugin::proc_macro::ProcMacroHost;
 
 pub mod defined_macros;
 pub mod expand_attribute;
+pub mod expand_derive;
 
 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

@@ -8,7 +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::expand::{ExpandAttribute, ExpandDerive};
 use scarb_proc_macro_server_types::methods::Method;
 use serde_json::Value;
 
@@ -74,6 +74,7 @@ fn route_request(proc_macros: Arc<ProcMacroHost>, request: RpcRequest) -> Result
         ExpandAttribute::METHOD => {
             run_handler::<ExpandAttribute>(proc_macros.clone(), request.value)
         }
+        ExpandDerive::METHOD => run_handler::<ExpandDerive>(proc_macros.clone(), request.value),
         _ => Err(anyhow!("method not found")),
     }
 }

scarb/tests/proc_macro_server.rs

@@ -5,6 +5,8 @@ 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_proc_macro_server_types::methods::expand::ExpandDerive;
+use scarb_proc_macro_server_types::methods::expand::ExpandDeriveParams;
 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;
@@ -88,3 +90,39 @@ fn expand_attribute() {
         TokenStream::new("fn very_new_name(){}".to_string())
     );
 }
+
+#[test]
+fn expand_derive() {
+    let t = TempDir::new().unwrap();
+    let plugin_package = t.child("some");
+
+    CairoPluginProjectBuilder::default()
+        .lib_rs(SIMPLE_MACROS)
+        .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 item = TokenStream::new("fn some_test_fn(){}".to_string());
+
+    let response = proc_macro_server
+        .request_and_wait::<ExpandDerive>(ExpandDeriveParams {
+            derives: vec!["some_derive".to_string()],
+            item,
+        })
+        .unwrap();
+
+    assert_eq!(response.diagnostics, vec![]);
+    assert_eq!(
+        response.token_stream,
+        TokenStream::new("impl SomeImpl of SomeTrait {}".to_string())
+    );
+}