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fix: give a useful error when ProjectionClass*D is missing #737

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fix: give a useful error when ProjectionClass*D is missing #737

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92c6979
fix: give a useful error when ProjectionClass*D is missing
FanxinSun Aug 5, 2026
d90a1c9
loop test with iest_issue_488() in test_issues.py got clean returns
FanxinSun Aug 11, 2026
667383e
Applying nit
FanxinSun Aug 11, 2026
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27 changes: 19 additions & 8 deletions src/vector/backends/awkward.py
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Original file line number Diff line number Diff line change
Expand Up @@ -584,6 +584,17 @@ def elements(self) -> tuple[ArrayOrRecord]:
return (self.tau,)


def _projection_class(
cls: type[VectorProtocol], dimension: int
) -> type[VectorProtocol]:
name = f"ProjectionClass{dimension}D"
projection: type[VectorProtocol] | None = getattr(cls, name, None)

@Saransh-cpp Saransh-cpp Aug 8, 2026

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Is the type explicitly required here? Does mypy complain?

@FanxinSun FanxinSun Aug 10, 2026

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I checked with:

mypy: 2.1.0
Python: 3.14.4

it will not complain. And this type annotation is not required, but one caveat is about warn_unreachable. Currently it's set false, by flipping it the un-annotated function will raise
error: Statement is unreachable [unreachable]
because ProjectionClass4D is declared non-Optional.

But in general I'm not clear about the plan of that flag so keeping it or not is up to you!

if not projection:
msg = f"{dimension}D conversion for {cls.__name__} is not defined"
raise TypeError(msg)
return projection


def _class_to_name(cls: type[VectorProtocol]) -> str:
# respect the type of classes inheriting VectorAwkward classes
is_vector = "vector.backends" in cls.__module__
Expand Down Expand Up @@ -742,11 +753,11 @@ def _wrap_result(
if any(
f in fields for f in ("t", "tau", "M", "m", "mass", "E", "e", "energy")
):
cls = cls.ProjectionClass4D
cls = _projection_class(cls, 4)
elif any(f in fields for f in ("z", "pz", "theta", "eta")):
cls = cls.ProjectionClass3D
cls = _projection_class(cls, 3)
else:
cls = cls.ProjectionClass2D
cls = _projection_class(cls, 2)

return maybe_record(
ak.zip(
Expand Down Expand Up @@ -788,7 +799,7 @@ def _wrap_result(
ak.zip(
dict(zip(names, arrays, strict=True)),
depth_limit=first.layout.purelist_depth,
with_name=_class_to_name(cls.ProjectionClass2D),
with_name=_class_to_name(_projection_class(cls, 2)),
behavior=None if vector._awkward_registered else first.behavior,
)
)
Expand Down Expand Up @@ -835,9 +846,9 @@ def _wrap_result(
if any(
f in fields for f in ("t", "tau", "M", "m", "mass", "E", "e", "energy")
):
cls = cls.ProjectionClass4D
cls = _projection_class(cls, 4)
else:
cls = cls.ProjectionClass3D
cls = _projection_class(cls, 3)

return maybe_record(
ak.zip(
Expand Down Expand Up @@ -891,7 +902,7 @@ def _wrap_result(
ak.zip(
dict(zip(names, arrays, strict=True)),
depth_limit=first.layout.purelist_depth,
with_name=_class_to_name(cls.ProjectionClass3D),
with_name=_class_to_name(_projection_class(cls, 3)),
behavior=None if vector._awkward_registered else first.behavior,
)
)
Expand Down Expand Up @@ -947,7 +958,7 @@ def _wrap_result(
ak.zip(
dict(zip(names, arrays, strict=True)),
depth_limit=first.layout.purelist_depth,
with_name=_class_to_name(cls.ProjectionClass4D),
with_name=_class_to_name(_projection_class(cls, 4)),
behavior=None if vector._awkward_registered else first.behavior,
)
)
Expand Down
34 changes: 34 additions & 0 deletions tests/test_issues.py
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Original file line number Diff line number Diff line change
Expand Up @@ -313,6 +313,40 @@ def test_issue_704():
assert isinstance(vec_vec.neg3D, vector.backends.awkward.MomentumArray4D)


def test_issue_488():
ak = pytest.importorskip("awkward")

coordinates = {
2: {"x": [1.1], "y": [2.2]},
3: {"x": [1.1], "y": [2.2], "z": [3.3]},
4: {"x": [1.1], "y": [2.2], "z": [3.3], "t": [4.4]},
}

for dimension, fields in coordinates.items():
mixin = getattr(vector.backends.awkward, f"VectorAwkward{dimension}D")

class VertexArray(mixin, ak.Array):
pass

class VertexRecord(mixin, ak.Record):
pass

# a subclass (like coffea's VertexArray) that defines GenericClass but
# deliberately no ProjectionClass*D, because it has no such interpretation
VertexArray.GenericClass = VertexArray
VertexRecord.GenericClass = VertexRecord

v = ak.zip(
fields,
with_name="Vertex",
behavior={("*", "Vertex"): VertexArray, "Vertex": VertexRecord},
)
with pytest.raises(
TypeError, match=f"{dimension}D conversion for VertexArray is not defined"
):
v.add(v)


def test_star_import_without_optional_deps():
"""from vector import * must not raise even when sympy/awkward are absent."""
# Block sympy via a find_spec-based meta path finder inserted before vector is imported.
Expand Down