From 1df5d052392da6ef9cd8bf993d59d1a20806ddad Mon Sep 17 00:00:00 2001
From: J Henry Waugh <jhwgh1968@protonmail.com>
Date: Sat, 8 Aug 2020 09:31:15 -0500
Subject: [PATCH] export_fn: allow duplicate Rust names

---
 codegen/src/function.rs         |  9 +++++--
 codegen/src/lib.rs              | 15 ++++++++++--
 codegen/tests/test_functions.rs | 42 ++++++++++++++++++++++++++++++++-
 3 files changed, 61 insertions(+), 5 deletions(-)

diff --git a/codegen/src/function.rs b/codegen/src/function.rs
index 88ff685d..f2e0ab11 100644
--- a/codegen/src/function.rs
+++ b/codegen/src/function.rs
@@ -4,7 +4,7 @@ use syn::{parse::Parse, parse::ParseStream, spanned::Spanned};
 
 #[derive(Debug, Default)]
 pub(crate) struct ExportedFnParams {
-    name: Option<String>,
+    pub name: Option<String>,
 }
 
 impl Parse for ExportedFnParams {
@@ -238,7 +238,12 @@ impl ExportedFn {
     }
 
     pub fn generate_impl(&self, on_type_name: &str) -> proc_macro2::TokenStream {
-        let name: syn::Ident = self.name().clone();
+        let name: syn::Ident = if let Some(ref name) = self.params.name {
+            syn::Ident::new(name, self.name().span())
+        } else {
+            self.name().clone()
+        };
+
         let arg_count = self.arg_count();
         let is_method_call = self.mutable_receiver();
 
diff --git a/codegen/src/lib.rs b/codegen/src/lib.rs
index 167bd0fb..8cc5bbd4 100644
--- a/codegen/src/lib.rs
+++ b/codegen/src/lib.rs
@@ -67,7 +67,7 @@
 //! ```
 //!
 
-use quote::{quote, quote_spanned};
+use quote::{quote, quote_spanned, ToTokens};
 use syn::{parse::Parser, parse_macro_input, spanned::Spanned};
 
 mod function;
@@ -79,9 +79,20 @@ pub fn export_fn(
     args: proc_macro::TokenStream,
     input: proc_macro::TokenStream,
 ) -> proc_macro::TokenStream {
-    let mut output = proc_macro2::TokenStream::from(input.clone());
+    let output = proc_macro2::TokenStream::from(input.clone());
+
     let parsed_params = parse_macro_input!(args as function::ExportedFnParams);
     let function_def = parse_macro_input!(input as function::ExportedFn);
+
+    let mut output = if let Some(ref rename) = parsed_params.name {
+        // If it wasn't a function, it wouldn't have parsed earlier, so unwrap() is fine.
+        let mut output_fn: syn::ItemFn = syn::parse2(output.clone()).unwrap();
+        let new_name = syn::Ident::new(rename, output_fn.sig.ident.span());
+        output_fn.sig.ident = new_name;
+        output_fn.into_token_stream()
+    } else {
+        output
+    };
     output.extend(function_def.generate_with_params(parsed_params));
     proc_macro::TokenStream::from(output)
 }
diff --git a/codegen/tests/test_functions.rs b/codegen/tests/test_functions.rs
index 24dba324..85fcede7 100644
--- a/codegen/tests/test_functions.rs
+++ b/codegen/tests/test_functions.rs
@@ -1,5 +1,5 @@
 use rhai::module_resolvers::*;
-use rhai::{Engine, EvalAltResult, Module, RegisterFn, FLOAT, INT};
+use rhai::{Array, Engine, EvalAltResult, Module, RegisterFn, FLOAT};
 
 pub mod raw_fn {
     use rhai::plugin::*;
@@ -190,3 +190,43 @@ fn rename_fn_test() -> Result<(), Box<EvalAltResult>> {
     );
     Ok(())
 }
+
+mod duplicate_fn_rename {
+    use rhai::plugin::*;
+    use rhai::{FLOAT, INT};
+
+    #[export_fn(name = "add_float")]
+    pub fn add(f1: FLOAT, f2: FLOAT) -> FLOAT {
+        f1 + f2
+    }
+
+    #[export_fn(name = "add_int")]
+    pub fn add(i1: INT, i2: INT) -> INT {
+        i1 + i2
+    }
+}
+
+#[test]
+fn duplicate_fn_rename_test() -> Result<(), Box<EvalAltResult>> {
+    let mut engine = Engine::new();
+    engine.register_fn("get_mystic_number", || 42 as FLOAT);
+    let mut m = Module::new();
+    rhai::register_exported_fn!(m, "add_two_floats", duplicate_fn_rename::add_float);
+    rhai::register_exported_fn!(m, "add_two_ints", duplicate_fn_rename::add_int);
+    let mut r = StaticModuleResolver::new();
+    r.insert("Math::Advanced".to_string(), m);
+    engine.set_module_resolver(Some(r));
+
+    let output_array = engine.eval::<Array>(
+        r#"import "Math::Advanced" as math;
+       let fx = get_mystic_number();
+       let fy = math::add_two_floats(fx, 1.0);
+       let ix = 42;
+       let iy = math::add_two_ints(ix, 1);
+       [fy, iy]
+       "#
+    )?;
+    assert_eq!(&output_array[0].as_float().unwrap(), &43.0);
+    assert_eq!(&output_array[1].as_int().unwrap(), &43);
+    Ok(())
+}