From 21fffc523e71e4f4661debc6067551c5dcf3ce69 Mon Sep 17 00:00:00 2001
From: Bas Schoenmaeckers <b.schoenmaeckers@zandersgroup.com>
Date: Wed, 3 Jun 2026 16:17:29 +0200
Subject: [PATCH] Add iter support to c-api

---
 crates/capi/src/abstract_.rs      |  10 +++
 crates/capi/src/abstract_/iter.rs | 129 ++++++++++++++++++++++++++++++
 2 files changed, 139 insertions(+)
 create mode 100644 crates/capi/src/abstract_/iter.rs

diff --git a/crates/capi/src/abstract_.rs b/crates/capi/src/abstract_.rs
index a677c98c7b4..01a3964f728 100644
--- a/crates/capi/src/abstract_.rs
+++ b/crates/capi/src/abstract_.rs
@@ -1,6 +1,7 @@
 use crate::{PyObject, pystate::with_vm};
 use alloc::slice;
 use core::ffi::c_int;
+pub use iter::*;
 pub use mapping::*;
 pub use number::*;
 use rustpython_vm::builtins::{PyDict, PyStr, PyTuple};
@@ -8,6 +9,7 @@ use rustpython_vm::function::{FuncArgs, KwArgs, PosArgs};
 use rustpython_vm::{AsObject, Py, PyObjectRef, PyResult, VirtualMachine};
 pub use sequence::*;
 
+mod iter;
 mod mapping;
 mod number;
 mod sequence;
@@ -170,3 +172,11 @@ pub unsafe extern "C" fn PyObject_IsInstance(inst: *mut PyObject, cls: *mut PyOb
         inst.is_instance(cls, vm)
     })
 }
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyObject_Size(obj: *mut PyObject) -> isize {
+    with_vm(|vm| {
+        let obj = unsafe { &*obj };
+        obj.length(vm)
+    })
+}
diff --git a/crates/capi/src/abstract_/iter.rs b/crates/capi/src/abstract_/iter.rs
new file mode 100644
index 00000000000..1ba5bd04d19
--- /dev/null
+++ b/crates/capi/src/abstract_/iter.rs
@@ -0,0 +1,129 @@
+use crate::{PyObject, pystate::with_vm};
+use core::ffi::c_int;
+use rustpython_vm::PyObjectRef;
+use rustpython_vm::builtins::PyGenerator;
+use rustpython_vm::protocol::{PyIter, PyIterReturn};
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyIter_Check(obj: *mut PyObject) -> c_int {
+    with_vm(|_vm| Ok(PyIter::check(unsafe { &*obj })))
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyObject_GetIter(obj: *mut PyObject) -> *mut PyObject {
+    with_vm(|vm| {
+        let obj = unsafe { &*obj };
+        obj.get_iter(vm).map(PyObjectRef::from)
+    })
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyIter_NextItem(iter: *mut PyObject, item: *mut *mut PyObject) -> c_int {
+    with_vm(|vm| {
+        unsafe {
+            *item = core::ptr::null_mut();
+        }
+
+        let iter = PyIter::new(unsafe { &*iter });
+        match iter.next(vm)? {
+            PyIterReturn::Return(next_item) => {
+                unsafe {
+                    *item = next_item.into_raw().as_ptr();
+                };
+                Ok(true)
+            }
+            PyIterReturn::StopIteration(_) => Ok(false),
+        }
+    })
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyIter_Next(iter: *mut PyObject) -> *mut PyObject {
+    with_vm(|vm| {
+        let iter = PyIter::new(unsafe { &*iter });
+        match iter.next(vm)? {
+            PyIterReturn::Return(next_item) => Ok(next_item.into_raw().as_ptr()),
+            PyIterReturn::StopIteration(_) => Ok(core::ptr::null_mut()),
+        }
+    })
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn PyIter_Send(
+    iter: *mut PyObject,
+    arg: *mut PyObject,
+    presult: *mut *mut PyObject,
+) -> c_int {
+    with_vm(|vm| {
+        unsafe {
+            *presult = core::ptr::null_mut();
+        }
+
+        let iter_obj = unsafe { &*iter };
+        let arg_obj = unsafe { &*arg };
+
+        let ret = if vm.is_none(arg_obj) {
+            PyIter::new(iter_obj).next(vm)?
+        } else {
+            iter_obj
+                .try_downcast_ref::<PyGenerator>(vm)?
+                .as_coro()
+                .send(iter_obj, arg_obj.to_owned(), vm)?
+        };
+
+        match ret {
+            PyIterReturn::Return(next_item) => {
+                unsafe {
+                    *presult = next_item.into_raw().as_ptr();
+                };
+                Ok(true)
+            }
+            PyIterReturn::StopIteration(ret_val) => {
+                let ret_val = ret_val.unwrap_or_else(|| vm.ctx.none());
+                unsafe {
+                    *presult = ret_val.into_raw().as_ptr();
+                };
+                Ok(false)
+            }
+        }
+    })
+}
+
+#[cfg(false)]
+mod tests {
+    use pyo3::prelude::*;
+    use pyo3::types::{PyAnyMethods, PyIterator, PyList, PySendResult};
+
+    #[test]
+    fn next_item() {
+        Python::attach(|py| {
+            let list = PyList::new(py, [1, 2, 3]).unwrap();
+            let iter = list.try_iter().unwrap();
+            let items: Vec<i32> = iter.map(|x| x.unwrap().extract::<i32>().unwrap()).collect();
+            assert_eq!(items, vec![1, 2, 3]);
+        })
+    }
+
+    #[test]
+    fn send_generator() {
+        Python::attach(|py| {
+            let generator = py
+                .eval(c"(x for x in (1, 2))", None, None)
+                .unwrap()
+                .cast_into::<PyIterator>()
+                .unwrap();
+
+            let first = generator.send(py.None().bind(py)).unwrap();
+            assert!(matches!(
+                first,
+                PySendResult::Next(value) if value.extract::<i32>().unwrap() == 1
+            ));
+
+            let second = generator.send(py.None().bind(py)).unwrap();
+            assert!(matches!(
+                second,
+                PySendResult::Next(value) if value.extract::<i32>().unwrap() == 2
+            ));
+        })
+    }
+}