numpy dependency not properly updated when version changed

[user202729]

Describe the bug

When numpy version changes (e.g. 1.26 → 2.1), meson setup --reconfigure need to explicitly be invoked otherwise missing header error messages results.

(more generally, how can run_command output be made dependent on something else?)

To Reproduce

# if there's a previous test environment delete it
conda deactivate
#conda env remove -n test

export PYTHONNOUSERSITE=1
conda create -n test python==3.12 numpy==1.26.4 meson ninja pkg-config
conda activate test

##

cat > hello_world.c << 'EOF'
#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include <numpy/arrayobject.h>

static PyObject* hello_world(PyObject* self, PyObject* args) {
    npy_intp dims[1] = {5};
    PyObject* array = PyArray_SimpleNew(1, dims, NPY_DOUBLE);
    
    if (array == NULL) {
        return NULL;
    }

    double* data = (double*) PyArray_DATA((PyArrayObject*) array);
    for (int i = 0; i < 5; i++) {
        data[i] = (double)(i + 1);
    }

    PyObject* repr = PyObject_Repr(array);
    const char* str = PyUnicode_AsUTF8(repr);
    printf("Hello, World! Here is a NumPy array: %s\n", str);

    Py_XDECREF(repr);
    Py_DECREF(array);
    
    Py_RETURN_NONE;
}

static PyMethodDef HelloWorldMethods[] = {
    {"hello", hello_world, METH_VARARGS, "Print 'Hello, World!' and a NumPy array"},
    {NULL, NULL, 0, NULL}
};

static struct PyModuleDef helloworldmodule = {
    PyModuleDef_HEAD_INIT,
    "hello_world",
    NULL,
    -1,
    HelloWorldMethods
};

PyMODINIT_FUNC PyInit_hello_world(void) {
    import_array();
    return PyModule_Create(&helloworldmodule);
}
EOF

cat > meson.build << 'EOF'
project('hello_world', 'c', version: '0.1.0')

py_module = import('python')
py = py_module.find_installation(pure: false)

inc_numpy = run_command(
  py,
  [ '-c', 'import numpy; print(numpy.get_include())' ],
  check: true,
).stdout().strip()
# following instruction in https://numpy.org/doc/stable/f2py/buildtools/meson.html#using-via-meson

numpy_dep = declare_dependency(include_directories: inc_numpy)
#numpy_dep = dependency('numpy')  # doesn't work because numpy-config isn't available before numpy 2.0

hello_world = py.extension_module('hello_world',
    'hello_world.c',
    dependencies: [numpy_dep],
    install: true,
)
EOF


meson setup ./build
meson compile -C ./build --verbose

conda install -y numpy==2.1.0

meson compile -C ./build --verbose

→

INFO: autodetecting backend as ninja
INFO: calculating backend command to run: /home/aaa/miniforge3/envs/test/bin/ninja -C /tmp/c/src/build -v
ninja: Entering directory `/tmp/c/src/build'
[1/2] ccache cc -Ihello_world.cpython-312-x86_64-linux-gnu.so.p -I. -I.. -I/home/aaa/miniforge3/envs/test/lib/python3.12/site-packages/numpy/core/include -I/home/aaa/miniforge3/envs/test/include/python3.12 -fvisibility=hidden -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -O0 -g -fPIC -MD -MQ hello_world.cpython-312-x86_64-linux-gnu.so.p/hello_world.c.o -MF hello_world.cpython-312-x86_64-linux-gnu.so.p/hello_world.c.o.d -o hello_world.cpython-312-x86_64-linux-gnu.so.p/hello_world.c.o -c ../hello_world.c
FAILED: hello_world.cpython-312-x86_64-linux-gnu.so.p/hello_world.c.o 
ccache cc -Ihello_world.cpython-312-x86_64-linux-gnu.so.p -I. -I.. -I/home/aaa/miniforge3/envs/test/lib/python3.12/site-packages/numpy/core/include -I/home/aaa/miniforge3/envs/test/include/python3.12 -fvisibility=hidden -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -O0 -g -fPIC -MD -MQ hello_world.cpython-312-x86_64-linux-gnu.so.p/hello_world.c.o -MF hello_world.cpython-312-x86_64-linux-gnu.so.p/hello_world.c.o.d -o hello_world.cpython-312-x86_64-linux-gnu.so.p/hello_world.c.o -c ../hello_world.c
../hello_world.c:3:10: fatal error: numpy/arrayobject.h: No such file or directory
    3 | #include <numpy/arrayobject.h>
      |          ^~~~~~~~~~~~~~~~~~~~~
compilation terminated.
ninja: build stopped: subcommand failed.

Expected behavior

The equivalent of meson setup --reconfigure ./build is automatically executed.

system parameters

• not cross-machine build
• Linux
• Python 3.12.0
• meson version 1.6.1
• ninja version 1.12.1