From 708c0f385e825cb14d66846a804d8c5d007ea416 Mon Sep 17 00:00:00 2001
From: J Henry Waugh <jhwgh1968@protonmail.com>
Date: Fri, 21 Aug 2020 22:30:10 -0500
Subject: [PATCH] Block #[cfg] attributes on exported or inner functions

---
 codegen/src/function.rs               | 10 ++++++++++
 codegen/src/module.rs                 | 11 +++++++++++
 codegen/ui_tests/export_fn_cfg.rs     | 25 +++++++++++++++++++++++++
 codegen/ui_tests/export_fn_cfg.stderr | 11 +++++++++++
 codegen/ui_tests/module_cfg_fn.rs     | 27 +++++++++++++++++++++++++++
 codegen/ui_tests/module_cfg_fn.stderr | 11 +++++++++++
 6 files changed, 95 insertions(+)
 create mode 100644 codegen/ui_tests/export_fn_cfg.rs
 create mode 100644 codegen/ui_tests/export_fn_cfg.stderr
 create mode 100644 codegen/ui_tests/module_cfg_fn.rs
 create mode 100644 codegen/ui_tests/module_cfg_fn.stderr

diff --git a/codegen/src/function.rs b/codegen/src/function.rs
index 0dba5afa..011ff650 100644
--- a/codegen/src/function.rs
+++ b/codegen/src/function.rs
@@ -148,6 +148,16 @@ impl Parse for ExportedFn {
         let entire_span = fn_all.span();
         let str_type_path = syn::parse2::<syn::Path>(quote! { str }).unwrap();
 
+        // #[cfg] attributes are not allowed on functions due to what is generated for them
+        if let Some(cfg_attr) = fn_all.attrs.iter().find(|a| {
+            a.path
+                .get_ident()
+                .map(|i| i.to_string() == "cfg")
+                .unwrap_or(false)
+        }) {
+            return Err(syn::Error::new(cfg_attr.span(), "cfg attributes not allowed on this item"));
+        }
+
         // Determine if the function is public.
         let is_public = match fn_all.vis {
             syn::Visibility::Public(_) => true,
diff --git a/codegen/src/module.rs b/codegen/src/module.rs
index c6bd6469..d3e09eca 100644
--- a/codegen/src/module.rs
+++ b/codegen/src/module.rs
@@ -16,6 +16,17 @@ use std::borrow::Cow;
 use std::collections::HashMap;
 
 fn inner_fn_attributes(f: &mut syn::ItemFn) -> syn::Result<ExportedFnParams> {
+    // #[cfg] attributes are not allowed on objects
+    if let Some(cfg_attr) = f.attrs.iter().find(|a| {
+        a.path
+            .get_ident()
+            .map(|i| i.to_string() == "cfg")
+            .unwrap_or(false)
+    }) {
+        return Err(syn::Error::new(cfg_attr.span(), "cfg attributes not allowed on this item"));
+    }
+
+    // Find the #[rhai_fn] attribute which will turn be read for the function parameters.
     if let Some(rhai_fn_idx) = f.attrs.iter().position(|a| {
         a.path
             .get_ident()
diff --git a/codegen/ui_tests/export_fn_cfg.rs b/codegen/ui_tests/export_fn_cfg.rs
new file mode 100644
index 00000000..52d4c963
--- /dev/null
+++ b/codegen/ui_tests/export_fn_cfg.rs
@@ -0,0 +1,25 @@
+use rhai::plugin::*;
+
+#[derive(Clone)]
+pub struct Point {
+    x: f32,
+    y: f32,
+}
+
+#[cfg(not(feature = "foo"))]
+#[export_fn]
+pub fn test_fn(input: Point) -> bool {
+    input.x > input.y
+}
+
+fn main() {
+    let n = Point {
+        x: 0.0,
+        y: 10.0,
+    };
+    if test_fn(n) {
+        println!("yes");
+    } else {
+        println!("no");
+    }
+}
diff --git a/codegen/ui_tests/export_fn_cfg.stderr b/codegen/ui_tests/export_fn_cfg.stderr
new file mode 100644
index 00000000..ac068be8
--- /dev/null
+++ b/codegen/ui_tests/export_fn_cfg.stderr
@@ -0,0 +1,11 @@
+error: cfg attributes not allowed on this item
+ --> $DIR/export_fn_cfg.rs:9:1
+  |
+9 | #[cfg(not(feature = "foo"))]
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0425]: cannot find function `test_fn` in this scope
+  --> $DIR/export_fn_cfg.rs:20:8
+   |
+20 |     if test_fn(n) {
+   |        ^^^^^^^ not found in this scope
diff --git a/codegen/ui_tests/module_cfg_fn.rs b/codegen/ui_tests/module_cfg_fn.rs
new file mode 100644
index 00000000..3613b9a5
--- /dev/null
+++ b/codegen/ui_tests/module_cfg_fn.rs
@@ -0,0 +1,27 @@
+use rhai::plugin::*;
+
+#[derive(Clone)]
+pub struct Point {
+    x: f32,
+    y: f32,
+}
+
+#[export_module]
+pub mod test_module {
+    #[cfg(not(feature = "foo"))]
+    pub fn test_fn(input: Point) -> bool {
+        input.x > input.y
+    }
+}
+
+fn main() {
+    let n = Point {
+        x: 0.0,
+        y: 10.0,
+    };
+    if test_module::test_fn(n) {
+        println!("yes");
+    } else {
+        println!("no");
+    }
+}
diff --git a/codegen/ui_tests/module_cfg_fn.stderr b/codegen/ui_tests/module_cfg_fn.stderr
new file mode 100644
index 00000000..80ac12f8
--- /dev/null
+++ b/codegen/ui_tests/module_cfg_fn.stderr
@@ -0,0 +1,11 @@
+error: cfg attributes not allowed on this item
+  --> $DIR/module_cfg_fn.rs:11:5
+   |
+11 |     #[cfg(not(feature = "foo"))]
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0433]: failed to resolve: use of undeclared type or module `test_module`
+  --> $DIR/module_cfg_fn.rs:22:8
+   |
+22 |     if test_module::test_fn(n) {
+   |        ^^^^^^^^^^^ use of undeclared type or module `test_module`