feat: add custom attributes to fn items

Cargo.toml

@@ -31,7 +31,7 @@ clang-sys = "1"
 clap = "4"
 clap_complete = "4"
 env_logger = "0.10.0"
-itertools = { version = ">=0.10,<0.14", default-features = false }
+itertools = { version = ">=0.10,<0.15", default-features = false, features = ["use_alloc"]}
 libloading = "0.8"
 log = "0.4"
 objc = "0.2"

bindgen-integration/Cargo.toml

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

bindgen-integration/build.rs

@@ -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;
@@ -140,7 +141,14 @@ impl ParseCallbacks for MacroCallback {
         info: &bindgen::callbacks::AttributeInfo<'_>,
     ) -> Vec<String> {
         if info.name == "Test" {
+            assert_eq!(info.kind, AttributeItemKind::Struct);
             vec!["#[cfg_attr(test, derive(PartialOrd))]".into()]
+        } else if info.name == "coord" {
+            assert_eq!(
+                info.kind,
+                AttributeItemKind::Function(FunctionKind::Function)
+            );
+            vec!["#[must_use]".into()]
         } else {
             vec![]
         }

bindgen-integration/src/lib.rs

@@ -297,6 +297,62 @@ 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::visit::Visit;
+    use syn::{parse_file, File, ForeignItem, Item, ItemForeignMod};
+
+    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");
+
+    struct FunctionVisitor {
+        found_coord: bool,
+        has_must_use: bool,
+    }
+
+    impl<'ast> Visit<'ast> for FunctionVisitor {
+        fn visit_item_foreign_mod(
+            &mut self,
+            foreign_mod: &'ast ItemForeignMod,
+        ) {
+            for foreign_item in &foreign_mod.items {
+                if let ForeignItem::Fn(item_fn) = foreign_item {
+                    if item_fn.sig.ident == "coord" {
+                        self.found_coord = true;
+                        self.has_must_use = item_fn
+                            .attrs
+                            .iter()
+                            .any(|attr| attr.path().is_ident("must_use"));
+                    }
+                }
+            }
+        }
+    }
+
+    let mut visitor = FunctionVisitor {
+        found_coord: false,
+        has_must_use: false,
+    };
+    visitor.visit_file(&syntax_tree);
+
+    assert!(
+        visitor.found_coord,
+        "The function 'coord' was not found in the source."
+    );
+    assert!(
+        visitor.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))])`

bindgen-tests/tests/headers/attribute-custom-cli.h

@@ -1,4 +1,4 @@
-// bindgen-flags: --default-enum-style rust --default-non-copy-union-style manually_drop --no-default=".*" --no-hash=".*" --no-partialeq=".*" --no-debug=".*" --no-copy=".*" --with-attribute-custom="foo_[^e].*=#[doc(hidden)]" --with-attribute-custom-struct="foo.*=#[derive(Default)]" --with-attribute-custom-enum="foo.*=#[cfg_attr(test, derive(PartialOrd, Copy))]" --with-attribute-custom-union="foo.*=#[derive(Clone)],#[derive(Copy)]"
+// bindgen-flags: --default-enum-style rust --default-non-copy-union-style manually_drop --no-default=".*" --no-hash=".*" --no-partialeq=".*" --no-debug=".*" --no-copy=".*" --with-attribute-custom="foo_[^e].*=#[doc(hidden)]" --with-attribute-custom-struct="foo.*=#[derive(Default)]" --with-attribute-custom-enum="foo.*=#[cfg_attr(test, derive(PartialOrd, Copy))]" --with-attribute-custom-union="foo.*=#[derive(Clone)],#[derive(Copy)]" --with-attribute-custom-function="foo.*=#[must_use],#[doc(hidden)]"
 struct foo_struct {
     int inner;
 };
@@ -12,3 +12,4 @@ union foo_union {
 struct non_matching {
     int inner;
 };
+int foo_function() { return 1; }

bindgen-tests/tests/headers/attribute-custom.h

@@ -26,3 +26,8 @@ struct my_type2 {
 struct my_type3 {
     unsigned long a;
 };
+
+/**
+ * <div rustbindgen attribute="#[must_use]" attribute="#[doc(hidden)]"></div>
+ */
+int function_attributes() { return 1; }

bindgen/callbacks.rs

@@ -3,7 +3,9 @@
 pub use crate::ir::analysis::DeriveTrait;
 pub use crate::ir::derive::CanDerive as ImplementsTrait;
 pub use crate::ir::enum_ty::{EnumVariantCustomBehavior, EnumVariantValue};
+pub use crate::ir::function::FunctionKind;
 pub use crate::ir::int::IntKind;
+use crate::HashSet;
 use std::fmt;
 
 /// An enum to allow ignoring parsing of macros.
@@ -133,9 +135,7 @@ pub trait ParseCallbacks: fmt::Debug {
     ///
     /// If no additional attributes are wanted, this function should return an
     /// empty `Vec`.
-    fn add_attributes(&self, _info: &AttributeInfo<'_>) -> Vec<String> {
-        vec![]
-    }
+    fn process_attributes(&self, _info: &AttributeInfo<'_>, _attributes: &mut HashSet<String>) {}
 
     /// Process a source code comment.
     fn process_comment(&self, _comment: &str) -> Option<String> {
@@ -231,15 +231,31 @@ pub struct DeriveInfo<'a> {
     pub kind: TypeKind,
 }
 
-/// Relevant information about a type to which new attributes will be added using
+/// Relevant information about an item to which new attributes will be added using
 /// [`ParseCallbacks::add_attributes`].
 #[derive(Debug)]
 #[non_exhaustive]
 pub struct AttributeInfo<'a> {
-    /// The name of the type.
+    /// The name of the item.
     pub name: &'a str,
-    /// The kind of the type.
-    pub kind: TypeKind,
+    /// The kind of the item.
+    pub kind: AttributeItemKind,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+/// The kind of the current item.
+pub enum AttributeItemKind {
+    /// The item is a Rust `struct`.
+    Struct,
+    /// The item is a Rust `enum`.
+    Enum,
+    /// The item is a Rust `union`.
+    Union,
+    /// The item is a Rust variable.
+    Var,
+    /// The item is a Rust `fn`.
+    Function(FunctionKind),
+    // TODO: Add `Alias` variant and more information about other items
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]