Migrated the metadata into PEP 621-compliant pyproject.toml (#138)

* Move the metadata from `setup.py` into `setup.cfg`.
Added `pyproject.toml`.
Removed `setup.py` - it is no longer needed.
Got rid of tests erroroneously finding their way into the wheel.

* Started populating version automatically from git tags using `setuptools_scm`.

* Migrated the metadata into `PEP 621`-compliant `pyproject.toml`, got rid of `setup.cfg`.

* test build in develop and pull requests

* use static version instead of dynamic git tag info

---------

Co-authored-by: KOLANICH <kolan_n@mail.ru>

.github/workflows/python-app.yml

@@ -23,7 +23,10 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install tox
+        pip install --upgrade setuptools setuptools_scm wheel build tox
     - name: Lint and test
       run: |
         tox
+    - name: Build
+      run: |
+        python -m build -nwsx .

.github/workflows/python-publish.yml

@@ -21,11 +21,11 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install setuptools wheel twine
+        pip install --upgrade setuptools setuptools_scm wheel build twine
     - name: Build and publish
       env:
         TWINE_USERNAME: ${{ secrets.PYPI_USERNAME }}
         TWINE_PASSWORD: ${{ secrets.PYPI_PASSWORD }}
       run: |
-        python setup.py sdist bdist_wheel
+        python -m build -nwsx .
         twine upload dist/*

pyproject.toml

@@ -0,0 +1,45 @@
+[build-system]
+requires = ["setuptools>=61.2", "setuptools_scm[toml]>=3.4.3"]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "markdownify"
+version = "0.13.0"
+authors = [{name = "Matthew Tretter", email = "m@tthewwithanm.com"}]
+description = "Convert HTML to markdown."
+readme = "README.rst"
+classifiers = [
+    "Environment :: Web Environment",
+    "Framework :: Django",
+    "Intended Audience :: Developers",
+    "License :: OSI Approved :: MIT License",
+    "Operating System :: OS Independent",
+    "Programming Language :: Python :: 2.5",
+    "Programming Language :: Python :: 2.6",
+    "Programming Language :: Python :: 2.7",
+    "Programming Language :: Python :: 3.6",
+    "Programming Language :: Python :: 3.7",
+    "Programming Language :: Python :: 3.8",
+    "Topic :: Utilities",
+]
+dependencies = [
+    "beautifulsoup4>=4.9,<5",
+    "six>=1.15,<2"
+]
+
+[project.urls]
+Homepage = "http://github.com/matthewwithanm/python-markdownify"
+Download = "http://github.com/matthewwithanm/python-markdownify/tarball/master"
+
+[project.scripts]
+markdownify = "markdownify.main:main"
+
+[tool.setuptools]
+zip-safe = false
+include-package-data = true
+
+[tool.setuptools.packages.find]
+include = ["markdownify", "markdownify.*"]
+namespaces = false
+
+[tool.setuptools_scm]