Allow callback composition (#2330)

* Allow callback composition

Store all the callbacks added to the builder in a `Vec` so bindgen
invokes each one of them in a last-to-first manner.

8 files changed, 69 insertions, 50 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index de08d829..560ce38b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -154,6 +154,8 @@
  * Regex inputs are sanitized so alternation (`a|b`) is handled correctly but
    wildcard patterns (`*`) are now considered invalid.
  * the `ParseCallbacks`trait does not require to implement `UnwindSafe`.
+ * the `Builder::parse_callbacks` method no longer overwrites previously added
+   callbacks and composes them in a last-to-first manner.
 
 ## Removed
 
diff --git a/bindgen/codegen/mod.rs b/bindgen/codegen/mod.rs
index bf0b3356..a59265ab 100644
--- a/bindgen/codegen/mod.rs
+++ b/bindgen/codegen/mod.rs
@@ -2112,12 +2112,11 @@ impl CodeGenerator for CompInfo {
 
         // The custom derives callback may return a list of derive attributes;
         // add them to the end of the list.
-        let custom_derives;
-        if let Some(cb) = &ctx.options().parse_callbacks {
-            custom_derives = cb.add_derives(&canonical_name);
-            // In most cases this will be a no-op, since custom_derives will be empty.
-            derives.extend(custom_derives.iter().map(|s| s.as_str()));
-        };
+        let custom_derives = ctx
+            .options()
+            .all_callbacks(|cb| cb.add_derives(&canonical_name));
+        // In most cases this will be a no-op, since custom_derives will be empty.
+        derives.extend(custom_derives.iter().map(|s| s.as_str()));
 
         if !derives.is_empty() {
             attributes.push(attributes::derives(&derives))
@@ -3152,12 +3151,10 @@ impl CodeGenerator for Enum {
 
             // The custom derives callback may return a list of derive attributes;
             // add them to the end of the list.
-            let custom_derives;
-            if let Some(cb) = &ctx.options().parse_callbacks {
-                custom_derives = cb.add_derives(&name);
-                // In most cases this will be a no-op, since custom_derives will be empty.
-                derives.extend(custom_derives.iter().map(|s| s.as_str()));
-            };
+            let custom_derives =
+                ctx.options().all_callbacks(|cb| cb.add_derives(&name));
+            // In most cases this will be a no-op, since custom_derives will be empty.
+            derives.extend(custom_derives.iter().map(|s| s.as_str()));
 
             attrs.push(attributes::derives(&derives));
         }
diff --git a/bindgen/ir/context.rs b/bindgen/ir/context.rs
index d987534d..928f2406 100644
--- a/bindgen/ir/context.rs
+++ b/bindgen/ir/context.rs
@@ -19,7 +19,6 @@ use super::module::{Module, ModuleKind};
 use super::template::{TemplateInstantiation, TemplateParameters};
 use super::traversal::{self, Edge, ItemTraversal};
 use super::ty::{FloatKind, Type, TypeKind};
-use crate::callbacks::ParseCallbacks;
 use crate::clang::{self, Cursor};
 use crate::parse::ClangItemParser;
 use crate::BindgenOptions;
@@ -619,15 +618,10 @@ If you encounter an error missing from this list, please file an issue or a PR!"
         )
     }
 
-    /// Get the user-provided callbacks by reference, if any.
-    pub fn parse_callbacks(&self) -> Option<&dyn ParseCallbacks> {
-        self.options().parse_callbacks.as_deref()
-    }
-
     /// Add another path to the set of included files.
     pub fn include_file(&mut self, filename: String) {
-        if let Some(cbs) = self.parse_callbacks() {
-            cbs.include_file(&filename);
+        for cb in &self.options().parse_callbacks {
+            cb.include_file(&filename);
         }
         self.deps.insert(filename);
     }
@@ -2240,19 +2234,24 @@ If you encounter an error missing from this list, please file an issue or a PR!"
             .or_insert_with(|| {
                 item.expect_type()
                     .name()
-                    .and_then(|name| match self.options.parse_callbacks {
-                        Some(ref cb) => cb.blocklisted_type_implements_trait(
-                            name,
-                            derive_trait,
-                        ),
-                        // Sized integer types from <stdint.h> get mapped to Rust primitive
-                        // types regardless of whether they are blocklisted, so ensure that
-                        // standard traits are considered derivable for them too.
-                        None => Some(if self.is_stdint_type(name) {
-                            CanDerive::Yes
+                    .and_then(|name| {
+                        if self.options.parse_callbacks.is_empty() {
+                            // Sized integer types from <stdint.h> get mapped to Rust primitive
+                            // types regardless of whether they are blocklisted, so ensure that
+                            // standard traits are considered derivable for them too.
+                            if self.is_stdint_type(name) {
+                                Some(CanDerive::Yes)
+                            } else {
+                                Some(CanDerive::No)
+                            }
                         } else {
-                            CanDerive::No
-                        }),
+                            self.options.last_callback(|cb| {
+                                cb.blocklisted_type_implements_trait(
+                                    name,
+                                    derive_trait,
+                                )
+                            })
+                        }
                     })
                     .unwrap_or(CanDerive::No)
             })
diff --git a/bindgen/ir/enum_ty.rs b/bindgen/ir/enum_ty.rs
index 059ee012..39677e93 100644
--- a/bindgen/ir/enum_ty.rs
+++ b/bindgen/ir/enum_ty.rs
@@ -102,8 +102,8 @@ impl Enum {
                     let name = cursor.spelling();
                     let annotations = Annotations::new(&cursor);
                     let custom_behavior = ctx
-                        .parse_callbacks()
-                        .and_then(|callbacks| {
+                        .options()
+                        .last_callback(|callbacks| {
                             callbacks
                                 .enum_variant_behavior(type_name, &name, val)
                         })
@@ -119,8 +119,8 @@ impl Enum {
                         });
 
                     let new_name = ctx
-                        .parse_callbacks()
-                        .and_then(|callbacks| {
+                        .options()
+                        .last_callback(|callbacks| {
                             callbacks.enum_variant_name(type_name, &name, val)
                         })
                         .or_else(|| {
diff --git a/bindgen/ir/function.rs b/bindgen/ir/function.rs
index c160ed81..f488b384 100644
--- a/bindgen/ir/function.rs
+++ b/bindgen/ir/function.rs
@@ -664,10 +664,11 @@ impl ClangSubItemParser for Function {
             // but seems easy enough to handle it here.
             name.push_str("_destructor");
         }
-        if let Some(callbacks) = context.parse_callbacks() {
-            if let Some(nm) = callbacks.generated_name_override(&name) {
-                name = nm;
-            }
+        if let Some(nm) = context
+            .options()
+            .last_callback(|callbacks| callbacks.generated_name_override(&name))
+        {
+            name = nm;
         }
         assert!(!name.is_empty(), "Empty function name.");
 
diff --git a/bindgen/ir/item.rs b/bindgen/ir/item.rs
index 1f4ac154..446d78bd 100644
--- a/bindgen/ir/item.rs
+++ b/bindgen/ir/item.rs
@@ -932,8 +932,8 @@ impl Item {
         let name = names.join("_");
 
         let name = if opt.user_mangled == UserMangled::Yes {
-            ctx.parse_callbacks()
-                .and_then(|callbacks| callbacks.item_name(&name))
+            ctx.options()
+                .last_callback(|callbacks| callbacks.item_name(&name))
                 .unwrap_or(name)
         } else {
             name
diff --git a/bindgen/ir/var.rs b/bindgen/ir/var.rs
index daaad8c5..198206b9 100644
--- a/bindgen/ir/var.rs
+++ b/bindgen/ir/var.rs
@@ -182,7 +182,7 @@ impl ClangSubItemParser for Var {
         use clang_sys::*;
         match cursor.kind() {
             CXCursor_MacroDefinition => {
-                if let Some(callbacks) = ctx.parse_callbacks() {
+                for callbacks in &ctx.options().parse_callbacks {
                     match callbacks.will_parse_macro(&cursor.spelling()) {
                         MacroParsingBehavior::Ignore => {
                             return Err(ParseError::Continue);
@@ -191,7 +191,7 @@ impl ClangSubItemParser for Var {
                     }
 
                     if cursor.is_macro_function_like() {
-                        handle_function_macro(&cursor, callbacks);
+                        handle_function_macro(&cursor, callbacks.as_ref());
                         // We handled the macro, skip macro processing below.
                         return Err(ParseError::Continue);
                     }
@@ -249,15 +249,15 @@ impl ClangSubItemParser for Var {
                             true,
                             ctx,
                         );
-                        if let Some(callbacks) = ctx.parse_callbacks() {
+                        for callbacks in &ctx.options().parse_callbacks {
                             callbacks.str_macro(&name, &val);
                         }
                         (TypeKind::Pointer(char_ty), VarType::String(val))
                     }
                     EvalResult::Int(Wrapping(value)) => {
                         let kind = ctx
-                            .parse_callbacks()
-                            .and_then(|c| c.int_macro(&name, value))
+                            .options()
+                            .last_callback(|c| c.int_macro(&name, value))
                             .unwrap_or_else(|| {
                                 default_macro_constant_type(ctx, value)
                             });
diff --git a/bindgen/lib.rs b/bindgen/lib.rs
index 4d72df0b..5e04acfe 100644
--- a/bindgen/lib.rs
+++ b/bindgen/lib.rs
@@ -1464,7 +1464,7 @@ impl Builder {
         mut self,
         cb: Box<dyn callbacks::ParseCallbacks>,
     ) -> Self {
-        self.options.parse_callbacks = Some(Rc::from(cb));
+        self.options.parse_callbacks.push(Rc::from(cb));
         self
     }
 
@@ -1982,7 +1982,7 @@ struct BindgenOptions {
 
     /// A user-provided visitor to allow customizing different kinds of
     /// situations.
-    parse_callbacks: Option<Rc<dyn callbacks::ParseCallbacks>>,
+    parse_callbacks: Vec<Rc<dyn callbacks::ParseCallbacks>>,
 
     /// Which kind of items should we generate? By default, we'll generate all
     /// of them.
@@ -2160,6 +2160,26 @@ impl BindgenOptions {
     pub fn rust_features(&self) -> RustFeatures {
         self.rust_features
     }
+
+    fn last_callback<T>(
+        &self,
+        f: impl Fn(&dyn callbacks::ParseCallbacks) -> Option<T>,
+    ) -> Option<T> {
+        self.parse_callbacks
+            .iter()
+            .filter_map(|cb| f(cb.as_ref()))
+            .last()
+    }
+
+    fn all_callbacks<T>(
+        &self,
+        f: impl Fn(&dyn callbacks::ParseCallbacks) -> Vec<T>,
+    ) -> Vec<T> {
+        self.parse_callbacks
+            .iter()
+            .flat_map(|cb| f(cb.as_ref()))
+            .collect()
+    }
 }
 
 impl Default for BindgenOptions {
@@ -2225,7 +2245,7 @@ impl Default for BindgenOptions {
             clang_args: vec![],
             input_headers: vec![],
             input_header_contents: Default::default(),
-            parse_callbacks: None,
+            parse_callbacks: Default::default(),
             codegen_config: CodegenConfig::all(),
             conservative_inline_namespaces: false,
             generate_comments: true,