Add the %pycached macro

Usage:

  %files
  ...
  %pycached %{python3_sitelib}/foo.py

This will list:

  /usr/lib/python3.8/site-packages/foo.py
  /usr/lib/python3.8/site-packages/__pycache__/foo.cpython-38{,.opt-?}.pyc

Assuming the Python 3 version is 3.8.
The bytecode files are globbed, their presence is not checked.

This will fail:

  %pycached %{python3_sitelib}/foo

error: %pycached can only be used with paths explicitly ending with .py

And so will any of this:

  %pycached %{python3_sitelib}/*
  %pycached %{python3_sitelib}/foo.*
  %pycached %{python3_sitelib}/foo.p?
  %pycached %{python3_sitelib}/foo.?y
  %pycached %{python3_sitelib}/foo.??

But this will work:

  %pycached %{python3_sitelib}/foo*.py

And it will generate the following globs:

  /usr/lib/python3.8/site-packages/foo*.py
  /usr/lib/python3.8/site-packages/__pycache__/foo*.cpython-38{,.opt-?}.pyc

When used with paths that include Python 3 version, it globs with the version:

  %pycached /opt/python3.10/foo.py

Generates:

  /opt/python3.10/foo.py
  /opt/python3.10/__pycache__/foo.cpython-310{,.opt-?}.pyc

While paths without version have less strict globs:

  %pycached /custom/foo.py
  /custom/foo.py
  /custom/__pycache__/foo.cpython-3*{,.opt-?}.pyc

This will generate a warning in RPM build:

warning: File listed twice: /custom/__pycache__/foo.cpython-38.opt-1.pyc

However it ensures the optimized bytecode is there.

macros.python3

@@ -37,3 +37,18 @@
 %py3_install_wheel() %{expand:\\\
   pip%{python3_version} install -I dist/%{1} --root %{buildroot} --no-deps
 }
+
+# This only supports Python 3.5+ and will never work with Python 2.
+# Hence, it has no Python version in the name.
+%pycached() %{lua:
+  path = rpm.expand("%{?1}")
+  if (string.sub(path, "-3") ~= ".py") then
+    rpm.expand("%{error:%%pycached can only be used with paths explicitly ending with .py}")
+  else
+    print(path)
+    pyminor = path:match("/python3.(%d+)/") or "*"
+    dirname = path:match("(.*/)")
+    modulename = path:match(".*/([^/]+).py")
+    print("\\n" .. dirname .. "__pycache__/" .. modulename .. ".cpython-3" .. pyminor .. "{,.opt-?}.pyc")
+  end
+}

python-rpm-macros.spec

@@ -80,6 +80,7 @@ install -m 644 %{SOURCE5} \
 %changelog
 * Sat Dec 28 2019 Miro Hrončok <mhroncok@redhat.com> - 3-51
 - Define %%python, but make it work only if %%__python is redefined
+- Add the %%pycached macro
 
 * Tue Nov 26 2019 Lumír Balhar <lbalhar@redhat.com> - 3-50
 - Update of bundled compileall2 module