Merge #3727

3727: Introduce ra_proc_macro r=matklad a=edwin0cheng

This PR implemented:

1.  Reading dylib path of proc-macro crate from cargo check , similar to how `OUTDIR` is obtained.
2.  Added a new crate `ra_proc_macro` and implement the foot-work for reading result from external proc-macro expander. 
3. Added a struct `ProcMacroClient` , which will be responsible to the client side communication to the External process.



Co-authored-by: Edwin Cheng <[email protected]>

1 files changed, 59 insertions, 0 deletions

diff --git a/crates/ra_proc_macro/src/lib.rs b/crates/ra_proc_macro/src/lib.rs
new file mode 100644
index 000000000..5e21dd487
--- /dev/null
+++ b/crates/ra_proc_macro/src/lib.rs
@@ -0,0 +1,59 @@
+//! Client-side Proc-Macro crate
+//!
+//! We separate proc-macro expanding logic to an extern program to allow
+//! different implementations (e.g. wasm or dylib loading). And this crate
+//! is used to provide basic infrastructure  for communication between two
+//! processes: Client (RA itself), Server (the external program)
+
+use ra_tt::{SmolStr, Subtree};
+use std::{
+    path::{Path, PathBuf},
+    sync::Arc,
+};
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ProcMacroProcessExpander {
+    process: Arc<ProcMacroProcessSrv>,
+    name: SmolStr,
+}
+
+impl ra_tt::TokenExpander for ProcMacroProcessExpander {
+    fn expand(
+        &self,
+        _subtree: &Subtree,
+        _attr: Option<&Subtree>,
+    ) -> Result<Subtree, ra_tt::ExpansionError> {
+        // FIXME: do nothing for now
+        Ok(Subtree::default())
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ProcMacroProcessSrv {
+    path: PathBuf,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ProcMacroClient {
+    Process { process: Arc<ProcMacroProcessSrv> },
+    Dummy,
+}
+
+impl ProcMacroClient {
+    pub fn extern_process(process_path: &Path) -> ProcMacroClient {
+        let process = ProcMacroProcessSrv { path: process_path.into() };
+        ProcMacroClient::Process { process: Arc::new(process) }
+    }
+
+    pub fn dummy() -> ProcMacroClient {
+        ProcMacroClient::Dummy
+    }
+
+    pub fn by_dylib_path(
+        &self,
+        _dylib_path: &Path,
+    ) -> Vec<(SmolStr, Arc<dyn ra_tt::TokenExpander>)> {
+        // FIXME: return empty for now
+        vec![]
+    }
+}