numpy 2.5.1: broadcast_to

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify numpy.broadcast_to in pkg:pypi/numpy@2.5.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:pypi/numpy@2.5.1
Demonstrate these symbols/APIs:
  - numpy.broadcast_to

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:1993163957d610a0d0df4506244a594a56920f1b2db5c0b7523af0ecf6428f23","contract":["assert numpy.broadcast_to broadcasts 1D array to compatible 2D shape producing a view with zero stride","assert numpy.broadcast_to broadcasts scalar and 0D array to arbitrary target shape","assert numpy.broadcast_to expands singleton dimensions to target shape","assert numpy.broadcast_to returns read-only view with writeable flag set to False","assert numpy.broadcast_to raises ValueError when target shape is incompatible with input shape","assert numpy.broadcast_to preserves ndarray subclasses when subok is True and forces base ndarray when subok is False"],"goal":"verify numpy.broadcast_to in pkg:pypi/numpy@2.5.1","kind":"HOW","packages":["pkg:pypi/numpy@2.5.1"],"schemaVersion":1,"symbols":["numpy.broadcast_to"]},"contractCommand":["python3","test/contract.py"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"pypi","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"pip","schemaVersion":1},"license":"MIT-0","packages":["pkg:pypi/numpy@2.5.1"],"schemaVersion":1,"subject":"pkg:pypi/numpy@2.5.1","symbols":["numpy.broadcast_to"],"verifierAdapter":"python@1"}

[project]
name = "verify-numpy-broadcast-to"
version = "0.1.0"
dependencies = [
    "numpy==2.5.1",
]

numpy==2.5.1

{
  "schemaVersion": 1,
  "goal": "verify numpy.broadcast_to in pkg:pypi/numpy@2.5.1",
  "kind": "HOW",
  "packages": [
    "pkg:pypi/numpy@2.5.1"
  ],
  "symbols": [
    "numpy.broadcast_to"
  ]
}

import numpy as np


def test_broadcast_to_1d_to_2d():
    arr = np.array([1, 2, 3])
    b = np.broadcast_to(arr, (2, 3))
    assert b.shape == (2, 3)
    assert np.array_equal(b, np.array([[1, 2, 3], [1, 2, 3]]))
    assert b.strides[0] == 0
    assert b.strides[1] == arr.strides[0]


def test_broadcast_to_scalar_and_0d():
    b_scalar = np.broadcast_to(7, (2, 3))
    assert b_scalar.shape == (2, 3)
    assert np.all(b_scalar == 7)

    arr_0d = np.array(42)
    b_0d = np.broadcast_to(arr_0d, (3, 1, 2))
    assert b_0d.shape == (3, 1, 2)
    assert np.all(b_0d == 42)


def test_broadcast_to_singleton_expansion():
    arr = np.array([[1], [2], [3]])
    b = np.broadcast_to(arr, (3, 4))
    assert b.shape == (3, 4)
    assert np.array_equal(b, np.array([[1, 1, 1, 1], [2, 2, 2, 2], [3, 3, 3, 3]]))
    assert b.strides == (arr.strides[0], 0)

    arr_2d = np.array([[10, 20], [30, 40]])
    b_3d = np.broadcast_to(arr_2d, (3, 2, 2))
    assert b_3d.shape == (3, 2, 2)
    assert b_3d.strides[0] == 0
    assert np.array_equal(b_3d[0], arr_2d)
    assert np.array_equal(b_3d[1], arr_2d)
    assert np.array_equal(b_3d[2], arr_2d)


def test_broadcast_to_readonly_view():
    arr = np.array([1, 2, 3])
    b = np.broadcast_to(arr, (2, 3))
    assert b.flags.writeable is False
    try:
        b[0, 0] = 99
        assert False, "Assignment to broadcast_to view should raise ValueError"
    except ValueError:
        pass


def test_broadcast_to_incompatible_shape():
    arr = np.array([1, 2, 3])
    try:
        np.broadcast_to(arr, (2, 2))
        assert False, "Incompatible shape should raise ValueError"
    except ValueError:
        pass
    try:
        np.broadcast_to(arr, (2,))
        assert False, "Incompatible shape should raise ValueError"
    except ValueError:
        pass


def test_broadcast_to_subok():
    class CustomArray(np.ndarray):
        pass

    sub_arr = np.array([1, 2, 3]).view(CustomArray)
    b_subok_true = np.broadcast_to(sub_arr, (2, 3), subok=True)
    assert isinstance(b_subok_true, CustomArray)
    assert b_subok_true.shape == (2, 3)

    b_subok_false = np.broadcast_to(sub_arr, (2, 3), subok=False)
    assert type(b_subok_false) is np.ndarray
    assert b_subok_false.shape == (2, 3)


def main():
    test_broadcast_to_1d_to_2d()
    test_broadcast_to_scalar_and_0d()
    test_broadcast_to_singleton_expansion()
    test_broadcast_to_readonly_view()
    test_broadcast_to_incompatible_shape()
    test_broadcast_to_subok()
    print("All contract assertions passed.")


if __name__ == "__main__":
    main()