Discovery callbacks for functions and methods.

This extends the existing discovery callback mechanism to report on functions
and methods. At this stage, we don't say much about them, in order to be
consistent with other discovery callbacks. Subsequent PRs will add
extra callbacks to provide information especially about methods
(virtualness, C++ visibility, etc.) Please request changes if you think
that sort of information should arrive in these callbacks.

Because methods are a fundamentally C++ thing, this splits the
current ParseCallbacks test to cover both a .h and a .hpp header.

Part of google/autocxx#124

bindgen-tests/tests/parse_callbacks/item_discovery_callback/header_item_discovery.h

@@ -25,4 +25,8 @@ enum NamedEnum {
     Fish,
 };
 
-typedef enum NamedEnum AliasOfNamedEnum;
+typedef enum NamedEnum AliasOfNamedEnum;
+
+// Functions
+
+void named_function();

bindgen-tests/tests/parse_callbacks/item_discovery_callback/header_item_discovery.hpp

@@ -0,0 +1,6 @@
+// Methods
+
+class SomeClass {
+public:
+    void named_method();
+};

bindgen-tests/tests/parse_callbacks/item_discovery_callback/mod.rs

@@ -17,20 +17,26 @@ impl ParseCallbacks for ItemDiscovery {
         self.0.borrow_mut().insert(_id, _item);
     }
 }
-#[test]
-pub fn test_item_discovery_callback() {
+
+fn test_item_discovery_callback(header: &str, expected: HashMap<DiscoveredItemId, DiscoveredItem>) {
     let discovery = ItemDiscovery::default();
     let info = Rc::clone(&discovery.0);
 
+    let mut header_path = env!("CARGO_MANIFEST_DIR").to_string();
+    header_path.push_str(header);
+
     Builder::default()
-        .header(concat!(
-        env!("CARGO_MANIFEST_DIR"),
-        "/tests/parse_callbacks/item_discovery_callback/header_item_discovery.h"
-        ))
+        .header(header_path)
         .parse_callbacks(Box::new(discovery))
         .generate()
         .expect("TODO: panic message");
 
+
+    compare_item_caches(&info.borrow(), &expected);
+}
+
+#[test]
+fn test_item_discovery_callback_c() {
     let expected = ItemCache::from([
         (
             DiscoveredItemId::new(10),
@@ -87,9 +93,38 @@ pub fn test_item_discovery_callback() {
                 final_name: "_bindgen_ty_*".to_string(),
             },
         ),
+        (
+            DiscoveredItemId::new(41),
+            DiscoveredItem::Function {
+                final_name: "named_function".to_string(),
+            },
+        ),
     ]);
+    test_item_discovery_callback(
+        "/tests/parse_callbacks/item_discovery_callback/header_item_discovery.h", expected);
+}
 
-    compare_item_caches(&info.borrow(), &expected);
+
+#[test]
+fn test_item_discovery_callback_cpp() {
+    let expected = ItemCache::from([
+        (
+            DiscoveredItemId::new(1),
+            DiscoveredItem::Struct {
+                original_name: Some("SomeClass".to_string()),
+                final_name: "SomeClass".to_string(),
+            },
+        ),
+        (
+            DiscoveredItemId::new(2),
+            DiscoveredItem::Method {
+                final_name: "named_method".to_string(),
+                parent: DiscoveredItemId::new(1),
+            },
+        ),
+    ]);
+    test_item_discovery_callback(
+        "/tests/parse_callbacks/item_discovery_callback/header_item_discovery.hpp", expected);
 }
 
 pub fn compare_item_caches(generated: &ItemCache, expected: &ItemCache) {
@@ -142,6 +177,12 @@ fn compare_item_info(
         DiscoveredItem::Enum { .. } => {
             compare_enum_info(expected_item, generated_item)
         }
+        DiscoveredItem::Function { .. } => {
+            compare_function_info(expected_item, generated_item)
+        }
+        DiscoveredItem::Method { .. } => {
+            compare_method_info(expected_item, generated_item)
+        }
     }
 }
 
@@ -279,3 +320,57 @@ pub fn compare_alias_info(
 
     compare_item_info(expected_aliased, generated_aliased, expected, generated)
 }
+
+pub fn compare_function_info(
+    expected_item: &DiscoveredItem,
+    generated_item: &DiscoveredItem,
+) -> bool {
+    let DiscoveredItem::Function {
+        final_name: expected_final_name,
+    } = expected_item
+    else {
+        unreachable!()
+    };
+
+    let DiscoveredItem::Function {
+        final_name: generated_final_name,
+    } = generated_item
+    else {
+        unreachable!()
+    };
+
+    if !compare_names(expected_final_name, generated_final_name) {
+        return false;
+    }
+    true
+}
+
+pub fn compare_method_info(
+    expected_item: &DiscoveredItem,
+    generated_item: &DiscoveredItem,
+) -> bool {
+    let DiscoveredItem::Method {
+        final_name: expected_final_name,
+        parent: expected_parent,
+    } = expected_item
+    else {
+        unreachable!()
+    };
+
+    let DiscoveredItem::Method {
+        final_name: generated_final_name,
+        parent: generated_parent,
+    } = generated_item
+    else {
+        unreachable!()
+    };
+
+    if expected_parent != generated_parent {
+        return false;
+    }
+
+    if !compare_names(expected_final_name, generated_final_name) {
+        return false;
+    }
+    true
+}

bindgen/callbacks.rs

@@ -224,7 +224,22 @@ pub enum DiscoveredItem {
         /// The final name of the generated binding
         final_name: String,
     },
-    // functions, modules, etc.
+
+    /// A function or method.
+    Function {
+        /// The final name used.
+        final_name: String,
+    },
+
+    /// A method.
+    Method {
+        /// The final name used.
+        final_name: String,
+
+        /// Type to which this method belongs.
+        parent: DiscoveredItemId,
+    }
+    // modules, etc.
 }
 
 /// Relevant information about a type to which new derive attributes will be added using

bindgen/codegen/mod.rs

@@ -2481,6 +2481,7 @@ impl CodeGenerator for CompInfo {
 
         let is_rust_union = is_union && struct_layout.is_rust_union();
 
+        let discovered_id = DiscoveredItemId::new(item.id().as_usize());
         ctx.options().for_each_callback(|cb| {
             let discovered_item = match self.kind() {
                 CompKind::Struct => DiscoveredItem::Struct {
@@ -2502,7 +2503,7 @@ impl CodeGenerator for CompInfo {
             };
 
             cb.new_item_found(
-                DiscoveredItemId::new(item.id().as_usize()),
+                discovered_id,
                 discovered_item,
             );
         });
@@ -2711,6 +2712,7 @@ impl CodeGenerator for CompInfo {
                         &mut method_names,
                         result,
                         self,
+                        discovered_id,
                     );
                 }
             }
@@ -2729,6 +2731,7 @@ impl CodeGenerator for CompInfo {
                         &mut method_names,
                         result,
                         self,
+                        discovered_id,
                     );
                 }
             }
@@ -2742,6 +2745,7 @@ impl CodeGenerator for CompInfo {
                         &mut method_names,
                         result,
                         self,
+                        discovered_id,
                     );
                 }
             }
@@ -2999,6 +3003,7 @@ impl Method {
         method_names: &mut HashSet<String>,
         result: &mut CodegenResult<'_>,
         _parent: &CompInfo,
+        parent_id: DiscoveredItemId,
     ) {
         assert!({
             let cc = &ctx.options().codegen_config;
@@ -3019,6 +3024,7 @@ impl Method {
 
         // First of all, output the actual function.
         let function_item = ctx.resolve_item(self.signature());
+        let id = DiscoveredItemId::new(function_item.id().as_usize());
         if !function_item.process_before_codegen(ctx, result) {
             return;
         }
@@ -3065,6 +3071,11 @@ impl Method {
 
         method_names.insert(name.clone());
 
+        ctx.options().for_each_callback(|cb| cb.new_item_found(id, DiscoveredItem::Method {
+            parent: parent_id,
+            final_name: name.clone(),
+        }));
+
         let mut function_name = function_item.canonical_name(ctx);
         if times_seen > 0 {
             write!(&mut function_name, "{times_seen}").unwrap();
@@ -4540,6 +4551,7 @@ impl CodeGenerator for Function {
     ) -> Self::Return {
         debug!("<Function as CodeGenerator>::codegen: item = {item:?}");
         debug_assert!(item.is_enabled_for_codegen(ctx));
+        let id = DiscoveredItemId::new(item.id().as_usize());
 
         let is_internal = matches!(self.linkage(), Linkage::Internal);
 
@@ -4650,6 +4662,14 @@ impl CodeGenerator for Function {
         if times_seen > 0 {
             write!(&mut canonical_name, "{times_seen}").unwrap();
         }
+        ctx.options().for_each_callback(|cb| {
+            cb.new_item_found(
+                id,
+                DiscoveredItem::Function {
+                    final_name: canonical_name.to_string(),
+                }
+            );
+        });
 
         let link_name_attr = self.link_name().or_else(|| {
             let mangled_name = mangled_name.unwrap_or(name);