Define %python, but make it work only if %__python is redefined

macros.python-srpm

@@ -11,6 +11,16 @@
 %python2 %__python2
 %python3 %__python3
 
+# Users can use %%python only if they redefined %%__python (e.g. to %%__python3)
+%python() %{lua:\
+    __python = rpm.expand("%__python")\
+    if __python == "/usr/bin/python" then\
+        rpm.expand("%{error:Cannot use %%python if %%__python wasn't redefined to something other than /usr/bin/python.}")\
+    else\
+        print(__python)\
+    end\
+}
+
 # python3_pkgversion specifies the version of Python 3 in the distro.  It can be
 # a specific version (e.g. 34 in Fedora EPEL7)
 %python3_pkgversion 3

python-rpm-macros.spec

@@ -1,6 +1,6 @@
 Name:           python-rpm-macros
 Version:        3
-Release:        43%{?dist}
+Release:        44%{?dist}
 Summary:        The unversioned Python RPM macros
 
 License:        MIT
@@ -73,6 +73,9 @@ install -m 644 %{SOURCE0} %{SOURCE1} %{SOURCE2} %{SOURCE3} %{SOURCE4} \
 
 
 %changelog
+* Sat Dec 28 2019 Miro Hrončok <mhroncok@redhat.com> - 3-44
+- Define %%python, but make it work only if %%__python is redefined
+
 * Fri Sep 27 2019 Miro Hrončok <mhroncok@redhat.com> - 3-43
 - Define %%python2 and %%python3