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[mlir][py] Mark all type caster from_{cpp,python} methods as noexcept #143866

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Merged
merged 5 commits into from
Jul 15, 2025
Merged

[mlir][py] Mark all type caster from_{cpp,python} methods as noexcept #143866

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35d5b50
[mlir][py] Mark all type caster `from_{cpp,python}` methods as noexcept
nicholasjng Jun 12, 2025
d7beef9
refactor: Change `mlirApiObjectToCapsule` to return std::optional
nicholasjng Jul 10, 2025
db8e35c
refactor: Assign in if statements everywhere, adjust test expectations
nicholasjng Jul 10, 2025
88e8038
Relax conversions to `nanobind::try_cast`
nicholasjng Jul 11, 2025
3fe682e
Merge branch 'main' into constexpr-from-cpp
makslevental Jul 15, 2025
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117 changes: 67 additions & 50 deletions mlir/include/mlir/Bindings/Python/NanobindAdaptors.h
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@
#define MLIR_BINDINGS_PYTHON_NANOBINDADAPTORS_H

#include <cstdint>
#include <optional>

#include "mlir-c/Diagnostics.h"
#include "mlir-c/IR.h"
Expand All @@ -43,18 +44,14 @@ namespace detail {
/// with a raw handle (unowned). The returned object's lifetime may not extend
/// beyond the apiObject handle without explicitly having its refcount increased
/// (i.e. on return).
static nanobind::object mlirApiObjectToCapsule(nanobind::handle apiObject) {
static std::optional<nanobind::object>
mlirApiObjectToCapsule(nanobind::handle apiObject) {
if (PyCapsule_CheckExact(apiObject.ptr()))
return nanobind::borrow<nanobind::object>(apiObject);
nanobind::object api =
nanobind::getattr(apiObject, MLIR_PYTHON_CAPI_PTR_ATTR, nanobind::none());
if (api.is_none()) {
std::string repr = nanobind::cast<std::string>(nanobind::repr(apiObject));
throw nanobind::type_error(
(llvm::Twine("Expected an MLIR object (got ") + repr + ").")
.str()
.c_str());
}
if (api.is_none())
return std::nullopt;
return api;
}

Expand All @@ -67,12 +64,11 @@ static nanobind::object mlirApiObjectToCapsule(nanobind::handle apiObject) {
template <>
struct type_caster<MlirAffineMap> {
NB_TYPE_CASTER(MlirAffineMap, const_name("MlirAffineMap"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToAffineMap(capsule.ptr());
if (mlirAffineMapIsNull(value)) {
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
if (!capsule)
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@makslevental makslevental Jul 10, 2025

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I did

    if (auto capsule = mlirApiObjectToCapsule(src))
      value = mlirPythonCapsuleToPassManager(capsule->ptr());

return false;
}
value = mlirPythonCapsuleToAffineMap(capsule.value().ptr());
return !mlirAffineMapIsNull(value);
}
static handle from_cpp(MlirAffineMap v, rv_policy,
Expand All @@ -90,9 +86,11 @@ struct type_caster<MlirAffineMap> {
template <>
struct type_caster<MlirAttribute> {
NB_TYPE_CASTER(MlirAttribute, const_name("MlirAttribute"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToAttribute(capsule.ptr());
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
if (!capsule)
return false;
value = mlirPythonCapsuleToAttribute(capsule.value().ptr());
return !mlirAttributeIsNull(value);
}
static handle from_cpp(MlirAttribute v, rv_policy,
Expand All @@ -111,9 +109,11 @@ struct type_caster<MlirAttribute> {
template <>
struct type_caster<MlirBlock> {
NB_TYPE_CASTER(MlirBlock, const_name("MlirBlock"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToBlock(capsule.ptr());
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
if (!capsule)
return false;
value = mlirPythonCapsuleToBlock(capsule.value().ptr());
return !mlirBlockIsNull(value);
}
};
Expand All @@ -122,7 +122,7 @@ struct type_caster<MlirBlock> {
template <>
struct type_caster<MlirContext> {
NB_TYPE_CASTER(MlirContext, const_name("MlirContext"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
if (src.is_none()) {
// Gets the current thread-bound context.
// TODO: This raises an error of "No current context" currently.
Expand All @@ -132,8 +132,8 @@ struct type_caster<MlirContext> {
.attr("Context")
.attr("current");
}
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToContext(capsule.ptr());
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToContext(capsule.value().ptr());
return !mlirContextIsNull(value);
}
};
Expand All @@ -142,9 +142,11 @@ struct type_caster<MlirContext> {
template <>
struct type_caster<MlirDialectRegistry> {
NB_TYPE_CASTER(MlirDialectRegistry, const_name("MlirDialectRegistry"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToDialectRegistry(capsule.ptr());
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
if (!capsule)
return false;
value = mlirPythonCapsuleToDialectRegistry(capsule.value().ptr());
return !mlirDialectRegistryIsNull(value);
}
static handle from_cpp(MlirDialectRegistry v, rv_policy,
Expand All @@ -162,15 +164,15 @@ struct type_caster<MlirDialectRegistry> {
template <>
struct type_caster<MlirLocation> {
NB_TYPE_CASTER(MlirLocation, const_name("MlirLocation"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
if (src.is_none()) {
// Gets the current thread-bound context.
src = nanobind::module_::import_(MAKE_MLIR_PYTHON_QUALNAME("ir"))
.attr("Location")
.attr("current");
}
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToLocation(capsule.ptr());
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToLocation(capsule.value().ptr());
return !mlirLocationIsNull(value);
}
static handle from_cpp(MlirLocation v, rv_policy,
Expand All @@ -188,9 +190,11 @@ struct type_caster<MlirLocation> {
template <>
struct type_caster<MlirModule> {
NB_TYPE_CASTER(MlirModule, const_name("MlirModule"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToModule(capsule.ptr());
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
if (!capsule)
return false;
value = mlirPythonCapsuleToModule(capsule.value().ptr());
return !mlirModuleIsNull(value);
}
static handle from_cpp(MlirModule v, rv_policy,
Expand All @@ -209,12 +213,15 @@ template <>
struct type_caster<MlirFrozenRewritePatternSet> {
NB_TYPE_CASTER(MlirFrozenRewritePatternSet,
const_name("MlirFrozenRewritePatternSet"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToFrozenRewritePatternSet(capsule.ptr());
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
if (!capsule)
return false;
value = mlirPythonCapsuleToFrozenRewritePatternSet(capsule.value().ptr());
return value.ptr != nullptr;
}
static handle from_cpp(MlirFrozenRewritePatternSet v, rv_policy, handle) {
static handle from_cpp(MlirFrozenRewritePatternSet v, rv_policy,
handle) noexcept {
nanobind::object capsule = nanobind::steal<nanobind::object>(
mlirPythonFrozenRewritePatternSetToCapsule(v));
return nanobind::module_::import_(MAKE_MLIR_PYTHON_QUALNAME("rewrite"))
Expand All @@ -228,9 +235,11 @@ struct type_caster<MlirFrozenRewritePatternSet> {
template <>
struct type_caster<MlirOperation> {
NB_TYPE_CASTER(MlirOperation, const_name("MlirOperation"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToOperation(capsule.ptr());
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
if (!capsule)
return false;
value = mlirPythonCapsuleToOperation(capsule.value().ptr());
return !mlirOperationIsNull(value);
}
static handle from_cpp(MlirOperation v, rv_policy,
Expand All @@ -250,9 +259,11 @@ struct type_caster<MlirOperation> {
template <>
struct type_caster<MlirValue> {
NB_TYPE_CASTER(MlirValue, const_name("MlirValue"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToValue(capsule.ptr());
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
if (!capsule)
return false;
value = mlirPythonCapsuleToValue(capsule.value().ptr());
return !mlirValueIsNull(value);
}
static handle from_cpp(MlirValue v, rv_policy,
Expand All @@ -273,9 +284,11 @@ struct type_caster<MlirValue> {
template <>
struct type_caster<MlirPassManager> {
NB_TYPE_CASTER(MlirPassManager, const_name("MlirPassManager"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToPassManager(capsule.ptr());
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
if (!capsule)
return false;
value = mlirPythonCapsuleToPassManager(capsule.value().ptr());
return !mlirPassManagerIsNull(value);
}
};
Expand All @@ -284,9 +297,11 @@ struct type_caster<MlirPassManager> {
template <>
struct type_caster<MlirTypeID> {
NB_TYPE_CASTER(MlirTypeID, const_name("MlirTypeID"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToTypeID(capsule.ptr());
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
if (!capsule)
return false;
value = mlirPythonCapsuleToTypeID(capsule.value().ptr());
return !mlirTypeIDIsNull(value);
}
static handle from_cpp(MlirTypeID v, rv_policy,
Expand All @@ -306,9 +321,11 @@ struct type_caster<MlirTypeID> {
template <>
struct type_caster<MlirType> {
NB_TYPE_CASTER(MlirType, const_name("MlirType"))
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) {
nanobind::object capsule = mlirApiObjectToCapsule(src);
value = mlirPythonCapsuleToType(capsule.ptr());
bool from_python(handle src, uint8_t flags, cleanup_list *cleanup) noexcept {
std::optional<nanobind::object> capsule = mlirApiObjectToCapsule(src);
if (!capsule)
return false;
value = mlirPythonCapsuleToType(capsule.value().ptr());
return !mlirTypeIsNull(value);
}
static handle from_cpp(MlirType t, rv_policy,
Expand Down
6 changes: 4 additions & 2 deletions mlir/test/python/lib/PythonTestModuleNanobind.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -113,8 +113,10 @@ NB_MODULE(_mlirPythonTestNanobind, m) {
.attr(MLIR_PYTHON_CAPI_VALUE_CASTER_REGISTER_ATTR)(
mlirRankedTensorTypeID)(
nanobind::cpp_function([valueCls](const nb::object &valueObj) {
nb::object capsule = mlirApiObjectToCapsule(valueObj);
MlirValue v = mlirPythonCapsuleToValue(capsule.ptr());
std::optional<nb::object> capsule =
mlirApiObjectToCapsule(valueObj);
// TODO(nicholasjng): Can this capsule be std::nullopt?
MlirValue v = mlirPythonCapsuleToValue(capsule.value().ptr());
MlirType t = mlirValueGetType(v);
// This is hyper-specific in order to exercise/test registering a
// value caster from cpp (but only for a single test case; see
Expand Down
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