Add developer install instructions

[banesullivan]

pip install -e .

does not work on Python 3.8 after cloning

$ pip install -e .
ERROR: File "setup.py" not found. Directory cannot be installed in editable mode: /Users/bane/Software/external/meshio
(A "pyproject.toml" file was found, but editable mode currently requires a setup.py based build.)

>>> import scooby
>>> scooby.Report(['setuptools', 'distutils'])

--------------------------------------------------------------------------------
  Date: Mon Nov 29 11:40:24 2021 MST

                OS : Darwin
            CPU(s) : 16
           Machine : x86_64
      Architecture : 64bit
       Environment : Python

  Python 3.8.8 | packaged by conda-forge | (default, Feb 20 2021, 16:12:38)
  [Clang 11.0.1 ]

        setuptools : 49.6.0.post20210108
         distutils : 3.8.8
             numpy : 1.20.2
             scipy : 1.6.3
           IPython : 7.22.0
        matplotlib : 3.4.1
            scooby : 0.5.7
--------------------------------------------------------------------------------

It appears the setup.py was removed (without warning?) in https://github.com/nschloe/meshio/pull/795

Since the typical way of installing isn't working, there should be an explanation of the usage of setup.cfg in the README and how to install this locally

[nschloe]

I just use tox for testing and install it with from pypi or pip install ..

[banesullivan]

But then you cannot edit the source and it be reflected in the environment. For example check this out:

I updated the init of meshio with this diff (after installing):

diff --git a/src/meshio/__init__.py b/src/meshio/__init__.py
index 035ae53..36c81ae 100644
--- a/src/meshio/__init__.py
+++ b/src/meshio/__init__.py
@@ -80,3 +80,5 @@ __all__ = [
     "topological_dimension",
     "__version__",
 ]
+
+print('this has been editted')

But then if I import meshio into Python, I cannot see that change:

$ meshio git:(main) ✗ python
Python 3.8.8 | packaged by conda-forge | (default, Feb 20 2021, 16:12:38)
[Clang 11.0.1 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import meshio
>>>

In order to see the change I have to install it again:

$ meshio git:(main) ✗ pip install .
...
$ meshio git:(main) ✗ python
Python 3.8.8 | packaged by conda-forge | (default, Feb 20 2021, 16:12:38)
[Clang 11.0.1 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import meshio
this has been editted
>>>

Without a setup.py there is no way to do a dev install (AFAIK)

[nschloe]

How about tox?

[banesullivan]

Well the point is that I want to use meshio in an arbitrary virtual env outside the context of tox and testing. Can the setup.py that was removed in #795 be added back?

[stefsmeets]

Without a setup.py there is no way to do a dev install (AFAIK)

This is also what I found. pip cannot do an editable install without a setup.py, so it seems that setup.cfg/pyproject.toml cannot completely replace setup.py yet.

[nschloe]

For the time being, you could simply add a setup.py locally.

[stefsmeets]

Yep, that's what I did 👍

[banesullivan]

A bit embarrassingly, this took me about an hour to figure out. IMO, meshio should keep a setup.py until the new package config can support editable installations

[banesullivan]

Or at least dev install instructions outlining the need for this file

[nschloe]

IMO, meshio should keep a setup.py until the new package config can support editable installations

Fair enough, fair enough. I'll add one.