build: specify dependencies directly in setup.cfg

In tox v4, "reuse of environments" was disabled [1]. This is then later
explained [2] to refer to exactly that thing which we were using for
inheriting the dependencies from the top-level testenv all the way to
the docs build. That's why the docs build in GitHub CI started failing.

IMHO, The Correct Way™ of specifying what dependencies are used for
which feature are the so-called "extra dependencies". Once they are in
place, it is be possible to install gnpy via, e.g., `pip install
oopt-gnpy[docs]`. However, this process is (as far as I can tell)
incompatible with `requirements.txt`; all my attempts at using the
standard dependency syntax in that file have failed for me.

So, in order to make this happen, let's move all the dependencies from a
more-or-less ad-hoc collection of files to this declarative approach
right in setup.cfg. That way, the deps are listed on a single place, in
a declarative manner, and as a result, the installation is now a trivial
pip oneliner.

As a result, one can also remove that duplication of dependencies in
docs requirements.

[1] https://tox.wiki/en/4.11.4/upgrading.html#reuse-of-environments
[2] https://tox.wiki/en/4.11.4/upgrading.html#packaging-configuration-and-inheritance

Change-Id: I34aa0c71e993b39e2b805a7de40e133b4d290318
Fixes: 47c89626 fix docs requirements

.github/workflows/main.yml

@@ -106,8 +106,7 @@ jobs:
         with:
           python-version: ${{ matrix.python_version }}
       - run: |
-          pip install -r tests/requirements.txt
-          pip install --editable .
+          pip install --editable .[tests]
           pytest -vv
     strategy:
       fail-fast: false
@@ -136,8 +135,7 @@ jobs:
         with:
           python-version: ${{ matrix.python_version }}
       - run: |
-          pip install -r tests/requirements.txt
-          pip install --editable .
+          pip install --editable .[tests]
           pytest -vv
     strategy:
       fail-fast: false

.readthedocs.yml

@@ -2,4 +2,3 @@ build:
     image: latest
 python:
     version: 3.8
-requirements_file: docs/requirements.txt

docs/requirements.txt

@@ -1,12 +0,0 @@
-alabaster>=0.7.12,<1
-docutils>=0.17.1,<1
-matplotlib>=3.7.3,<4
-myst-parser>=0.16.1,<1
-networkx>=3.1,<4
-numpy>=1.24.4,<2
-Pygments>=2.11.2,<3
-rstcheck
-scipy>=1.10.1,<2
-Sphinx>=5.3.0,<6
-sphinxcontrib-bibtex>=2.4.1,<3
-xlrd>=1.2.0,<2

requirements.txt

@@ -1,11 +0,0 @@
-# matplotlib 3.8 removed support for Python 3.8
-matplotlib>=3.7.3,<4
-# networkx 3.2 removed support for Python 3.8
-networkx>=3.1,<4
-# numpy 1.25 removed support for Python 3.8
-numpy>=1.24.4,<2
-pbr>=6.0.0,<7
-# scipy 1.11 removed support for Python 3.8
-scipy>=1.10.1,<2
-# xlrd 2.x removed support for .xlsx, it's only .xls now
-xlrd>=1.2.0,<2

setup.cfg

@@ -49,3 +49,35 @@ console_scripts =
     gnpy-transmission-example = gnpy.tools.cli_examples:transmission_main_example
     gnpy-path-request = gnpy.tools.cli_examples:path_requests_run
     gnpy-convert-xls = gnpy.tools.convert:_do_convert
+
+[options]
+install_requires =
+	# matplotlib 3.8 removed support for Python 3.8
+	matplotlib>=3.7.3,<4
+	# networkx 3.2 removed support for Python 3.8
+	networkx>=3.1,<4
+	# numpy 1.25 removed support for Python 3.8
+	numpy>=1.24.4,<2
+	pbr>=6.0.0,<7
+	# scipy 1.11 removed support for Python 3.8
+	scipy>=1.10.1,<2
+	# xlrd 2.x removed support for .xlsx, it's only .xls now
+	xlrd>=1.2.0,<2
+
+[options.extras_require]
+tests =
+	build>=1.0.3,<2
+	pytest>=7.4.3,<8
+	# pandas 2.1 removed support for Python 3.8
+	pandas>=2.0.3,<3
+	# flake v6 killed the --diff option
+	flake8>=5.0.4,<6
+
+docs =
+	alabaster>=0.7.12,<1
+	docutils>=0.17.1,<1
+	myst-parser>=0.16.1,<1
+	Pygments>=2.11.2,<3
+	rstcheck
+	Sphinx>=5.3.0,<6
+	sphinxcontrib-bibtex>=2.4.1,<3

tests/requirements.txt

@@ -1,7 +0,0 @@
-build>=1.0.3,<2
-pytest>=7.4.3,<8
-# pandas 2.1 removed support for Python 3.8
-pandas>=2.0.3,<3
-
-# flake v6 killed the --diff option
-flake8>=5.0.4,<6

tox.ini

@@ -2,9 +2,8 @@
 skipsdist = True
 
 [testenv]
+extras = tests
 deps =
-	-r{toxinidir}/requirements.txt
-	-r{toxinidir}/tests/requirements.txt
 	cover: pytest-cov
 	linters: flake8
 	linters: pep8-naming
@@ -22,8 +21,7 @@ commands =
 	python -m build
 
 [testenv:docs]
-deps =
-	-r{toxinidir}/docs/requirements.txt
+extras = docs
 allowlist_externals =
 	/bin/sh
 commands =