Proposal for generating scl-specific macros automatically

a.spec

# To try, install python27-macros and rpmbuild -bp this spec
# Then see what it prints
# Uncomment this to get unversioned %%python_datadir macro
# %%python27_make_default_macros

Name:           a
Version:        1
Release:        1%{?dist}
Summary:        a

License:        MIT
URL:            http://a

%description
a.

%prep
echo %python27_datadir
# echo %%python_datadir

%build

%install

%files

%changelog

macros.genscl

# arguments to scl_generate_macros:
#  %1 - prefix for general macros
#  %2 - where to save the file
%scl_generate_macros() %{expand:
cat >> %2/macros.%{scl}-general << EOF
%%%{expand:%{scl}_datadir} %_datadir
# if %{scl}_make_default_macros is defined, generate default macros
# (if RPM doesn't work, just add more percent signs)
%%%{scl}_make_default_macros() %%%%{expand:
%%%%global %{expand:%{1}_datadir %_datadir}
}
EOF
}

python27.spec

diff --git a/python27.spec b/python27.spec
index 22f496a..9e425f3 100644
--- a/python27.spec
+++ b/python27.spec
@@ -42,6 +42,12 @@ Requires: scl-utils-build
 %description build
 Package shipping essential configuration macros to build %scl Software Collection.
 
+%package macros
+Summary: Package shipping macros specific to this collection
+
+%description macros
+Package shipping macros specific to this collection.
+
 %prep
 %setup -T -c
 
@@ -59,6 +65,7 @@ export XDG_DATA_DIRS=%{_datadir}\${XDG_DATA_DIRS:+:\${XDG_DATA_DIRS}}
 export PKG_CONFIG_PATH=%{_libdir}/pkgconfig\${PKG_CONFIG_PATH:+:\${PKG_CONFIG_PATH}}
 EOF
 %scl_install
+%scl_generate_macros python %{buildroot}%{_root_sysconfdir}/rpm
 
 # Add the aditional macros to macros.%%{scl}-config
 cat %{SOURCE0} >> %{buildroot}%{_root_sysconfdir}/rpm/macros.%{scl}-config
@@ -72,6 +79,9 @@ sed -i 's|@scl@|%{scl}|g' %{buildroot}%{_root_sysconfdir}/rpm/macros.%{scl}-conf
 %files build
 %{_root_sysconfdir}/rpm/macros.%{scl}-config
 
+%files macros
+%{_root_sysconfdir}/rpm/macros.%{scl}-general
+
 %changelog
 * Wed Oct 23 2013 Robert Kuska <rkuska@redhat.com> - 1-13
 - Remove blank line from macros.additional.python27