# F2PY CLI tests study

Path - https://github.com/HaoZeke/numpy/blob/f2py2eTests/numpy/f2py/tests/test_f2py2e.py

- Used to test the frontend CLI of F2PY
- Tests use [`hello_world_f90`, `hello_world_f77`, `retreal_f77`] fixtures that return `tmpdir` file paths.
- `monkeypatch` fixture patches the command line input (for eg - it changes `pytest runtests.py` to `f2py -h fibfortran.py`).
- `f2pycli()`function when executed reads the patched command line and executes F2PY.

- **[get_io_paths()](https://github.com/HaoZeke/numpy/blob/f9ee4527726df63d4bedcb14d349dc9e67f84367/numpy/f2py/tests/test_f2py2e.py#L17)**
- Returns expected path of output files generated by F2PY after parsing input fortran file. (any of [`hello_world_f90`, `hello_world_f77`, `retreal_f77`] for ex)
- Output files generated by F2PY might include pyf, f77 or f90 wrappers and C API module file

### Doubts
- **[test_gen_pyf_stdout](https://github.com/HaoZeke/numpy/blob/f9ee4527726df63d4bedcb14d349dc9e67f84367/numpy/f2py/tests/test_f2py2e.py#L98)**
- L99. Why are we not testing if pyf file has been written to the stdout. In `test_gen_pyf` we tested that output pyf file was indeed generated?

- **[test_inclpath](https://github.com/HaoZeke/numpy/blob/f9ee4527726df63d4bedcb14d349dc9e67f84367/numpy/f2py/tests/test_f2py2e.py#L518)**
- Need help understanding --include-paths usage.
- Determine how to test this flag.

- **-c -help-fcompiler**
- Why is `-c` flag necessary to invoke `--help-fcompiler`

### Testing Plans:
- [test_f2cmap](https://github.com/HaoZeke/numpy/blob/f9ee4527726df63d4bedcb14d349dc9e67f84367/numpy/f2py/tests/test_f2py2e.py#L536)
- --f2cmap flag lacks [documentation](https://numpy.org/doc/stable/f2py/usage.html)
- Create a temp file .f2py_f2cmap. Write test f2cmap config and test the generate C API module.
- [test_hlink](https://github.com/HaoZeke/numpy/blob/f2py2eTests/numpy/f2py/tests/test_f2py2e.py#L527)
1. Output result of `f2py --help-link` to stdout or a tempfile.
2. Search for various terms like - `fft_opt_info, C compiler, fftw_info,...` etc.

## distutils Flag Meson alternatives

| Flag | Alternative |
| -------- | -------- |
| `--help-fcompiler` | No alternative found |
| `--fcompiler` | [Set FC Flag](https://mesonbuild.com/Reference-tables.html#compiler-and-linker-selection-variables) |
| `--compiler` | Set CC Flag |

**Native File reference Meson**
Native files can be used to specify compiler Paths and Flags - [Native Files - Meson](https://mesonbuild.com/Machine-files.html)
- Study the meson build system this weekend and understand [NumPy, Meson and F2PY](https://rgoswami.me/posts/numpy-meson-f2py/)
- Native file examples show C program compilation, find out Fortran compilationg using Native file

### Interactive F2PY development
- Get the environment setup

micromamba create -f environment.yml
micromamba activate numpy-dev
pip install -e . # EDITABLE MODE

Now somewhere in `f2py` sources (only works for the `.py` sources, full rebuilds needed for `.{c,h}` changes):

# Add a breakpoint anywhere
breakpoint()

Finally, run some code, any code which is expected to go over the breakpoint. This will drop you into an interactive `pdb` session.

### Test case

subroutine foo()
print*, "Hello"
end subroutine foo

^ Given this

- We want to have `f2py -c hello.f90 -m blah` generate a `cpython` module which works (but is built with `meson`)
- We want to have `f2py -m blah hello.f90` generate a `build` directory which contains `meson.build` which code generated

Basically automating this [part of the documentation](https://numpy.org/doc/stable/f2py/buildtools/meson.html)

### Helpful things
- `nm` --> https://en.wikipedia.org/wiki/Nm_%28Unix%29