feat(bindgen-integration): add test for custom fn attributes

Author: rich-ayr

Cargo.lock

@@ -10,6 +10,9 @@ build = "build.rs"
 rust-version.workspace = true
 edition.workspace = true
 
+[dependencies]
+syn = { workspace = true, features = ["full"] }
+
 [build-dependencies]
 bindgen = { workspace = true, default-features = true, features = ["experimental"] }
 cc.workspace = true

bindgen-integration/Cargo.toml

@@ -1,7 +1,8 @@
 extern crate bindgen;
 
 use bindgen::callbacks::{
-    DeriveInfo, IntKind, MacroParsingBehavior, ParseCallbacks,
+    AttributeItemKind, DeriveInfo, FunctionKind, IntKind, MacroParsingBehavior,
+    ParseCallbacks,
 };
 use bindgen::{Builder, EnumVariation, Formatter};
 use std::collections::HashSet;
@@ -140,10 +141,16 @@ impl ParseCallbacks for MacroCallback {
         info: &bindgen::callbacks::AttributeInfo<'_>,
     ) -> Vec<String> {
         if info.name == "Test" {
-            vec!["#[cfg_attr(test, derive(PartialOrd))]".into()]
-        } else {
-            vec![]
+            assert!(info.kind == AttributeItemKind::Struct);
+            return vec!["#[cfg_attr(test, derive(PartialOrd))]".into()];
+        } else if info.name == "coord" {
+            assert!(
+                info.kind ==
+                    AttributeItemKind::Function(FunctionKind::Function)
+            );
+            return vec!["#[must_use]".into()];
         }
+        return vec![];
     }
 }
 

bindgen-integration/build.rs

@@ -297,6 +297,49 @@ fn test_custom_derive() {
     assert!(!(test1 > test2));
 }
 
+#[test]
+fn test_custom_fn_attribute() {
+    use std::env;
+    use std::fs;
+    use std::path::Path;
+    use syn::{parse_file, File, Item, ItemFn};
+
+    let out_dir =
+        std::env::var("OUT_DIR").expect("OUT_DIR environment variable not set");
+    let test_file_path = Path::new(&out_dir).join("test.rs");
+    let file_content = fs::read_to_string(&test_file_path)
+        .expect("Failed to read test.rs file");
+    let syntax_tree: File =
+        parse_file(&file_content).expect("Failed to parse test.rs");
+
+    let mut found_coord = false;
+    let mut has_must_use = false;
+
+    for item in syntax_tree.items {
+        if let Item::Fn(item_fn) = item {
+            if item_fn.sig.ident == "coord" {
+                found_coord = true;
+                has_must_use = item_fn.attrs.iter().any(|attr| {
+                    if let Ok(meta) = attr.parse_meta() {
+                        meta.path().is_ident("must_use")
+                    } else {
+                        false
+                    }
+                });
+            }
+        }
+    }
+
+    assert!(
+        found_coord,
+        "The function 'coord' was not found in the source."
+    );
+    assert!(
+        has_must_use,
+        "The function 'coord' does not have the #[must_use] attribute."
+    );
+}
+
 #[test]
 fn test_custom_attributes() {
     // The `add_attributes` callback should have added `#[cfg_attr(test, derive(PartialOrd))])`