Support distro specific child templates

Support jinja child templates in renderspec/dist-templates which are
automatically used with corresponding --spec-style and allow different
output for each spec style (distro) using jinja `{% block %}` syntax.

Also enable trim_blocks to keep resulting specs clean.

Change-Id: I7c082e56836f06fb98881adc4cdf63d8626f4d7b

doc/source/usage.rst

@@ -163,6 +163,37 @@ With the `suse` spec-style::
 
   License: Apache-2.0
 
+
+distribution specific blocks & child templates
+**********************************************
+
+To properly handle differences between individual .spec styles, renderspec
+contains child templates in `renderspec/dist-templates` which are
+automatically used with corresponding `--spec-style`. These allow different
+output for each spec style (distro) using jinja `{% block %}` syntax.
+
+For example consider simple `renderspec/dist-templates/fedora.spec.j2`:
+
+  {% extends ".spec" %}
+  {% block build_requires %}
+  BuildRequires:  {{ py2pkg('setuptools') }}
+  {% endblock %}
+
+allows following in a spec template:
+
+  {% block build_requires %}{% endblock %}
+
+to render into
+
+  BuildRequires:  python-setuptools
+
+with `fedora` spec style, while `renderspec/dist-templates/suse.spec.j2` might
+define other result for `suse` spec style.
+
+For more information, see current `renderspec/dist-templates` and usage in
+`openstack/rpm-packaging`_ project.
+
+
 .. _Jinja2: http://jinja.pocoo.org/docs/dev/
 .. _openstack/rpm-packaging: https://git.openstack.org/cgit/openstack/rpm-packaging/
 .. _pymod2pkg: https://git.openstack.org/cgit/openstack/pymod2pkg

renderspec/__init__.py

@@ -24,11 +24,11 @@ import sys
 from jinja2 import contextfilter
 from jinja2 import contextfunction
 from jinja2 import Environment
-from jinja2 import FileSystemLoader
 import pymod2pkg
 
 import yaml
 
+from renderspec.distloader import RenderspecLoader
 from renderspec import versions
 
 
@@ -147,12 +147,17 @@ def _env_register_filters_and_globals(env):
 
 def generate_spec(spec_style, epochs, requirements, input_template_path):
     """generate a spec file with the given style and the given template"""
-    env = Environment(loader=FileSystemLoader(
-        os.path.dirname(input_template_path)))
+
+    env = Environment(loader=RenderspecLoader(
+        template_fn=input_template_path),
+        trim_blocks=True)
 
     _env_register_filters_and_globals(env)
 
-    template = env.get_template(os.path.basename(input_template_path))
+    template_name = '.spec'
+    if spec_style in env.loader.list_templates():
+        template_name = spec_style
+    template = env.get_template(template_name)
     return template.render(spec_style=spec_style, epochs=epochs,
                            requirements=requirements)
 

renderspec/dist-templates/fedora.spec.j2

@@ -0,0 +1,4 @@
+{% extends ".spec" %}
+{% block build_requires %}
+BuildRequires:  {{ py2pkg('setuptools') }}
+{% endblock %}

renderspec/dist-templates/suse.spec.j2

@@ -0,0 +1,4 @@
+{% extends ".spec" %}
+{% block build_requires %}
+BuildRequires:  openstack-macros
+{% endblock %}

renderspec/distloader.py

@@ -0,0 +1,76 @@
+#!/usr/bin/python
+# Copyright (c) 2016 Red Hat
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import jinja2
+from jinja2.loaders import TemplateNotFound
+from jinja2.utils import open_if_exists
+import os
+
+
+def get_dist_templates_path():
+    return os.path.join(os.path.dirname(__file__), 'dist-templates')
+
+
+class RenderspecLoader(jinja2.BaseLoader):
+    """A special template loader which allows rendering supplied .spec template
+    with distro specific blocks maintained as part of renderspec.
+
+    '.spec' returns the spec template (which you need to supply during init)
+    while other strings map to corresponding child templates included
+    in renderspec which simply extend the '.spec' template.
+    """
+    base_ref = '.spec'
+    template_postfix = '.spec.j2'
+
+    def __init__(self, template_fn, encoding='utf-8'):
+        self.base_fn = template_fn
+        self.encoding = encoding
+        self.disttemp_path = get_dist_templates_path()
+
+    def get_source(self, environment, template):
+        if template == self.base_ref:
+            fn = self.base_fn
+        else:
+            fn = os.path.join(self.disttemp_path,
+                              template + self.template_postfix)
+
+        f = open_if_exists(fn)
+        if not f:
+            return TemplateNotFound(template)
+        try:
+            contents = f.read().decode(self.encoding)
+        finally:
+            f.close()
+
+        mtime = os.path.getmtime(self.base_fn)
+
+        def uptodate():
+            try:
+                return os.path.getmtime(self.base_fn) == mtime
+            except OSError:
+                return False
+
+        return contents, fn, uptodate
+
+    def list_templates(self):
+        found = set([self.base_ref])
+        walk_dir = os.walk(self.disttemp_path)
+        for _, _, filenames in walk_dir:
+            for fn in filenames:
+                if fn.endswith(self.template_postfix):
+                    template = fn[:-len(self.template_postfix)]
+                    found.add(template)
+        return sorted(found)

tests.py

@@ -24,7 +24,7 @@ from ddt import data, ddt, unpack
 
 from jinja2 import Environment
 
-from mock import Mock
+from mock import Mock, patch
 import os
 import renderspec
 import renderspec.versions
@@ -297,5 +297,41 @@ class RenderspecDistroDetection(unittest.TestCase):
         self.assertEqual(renderspec._get_default_distro(), "unknown")
 
 
+class RenderspecDistTeamplatesTests(unittest.TestCase):
+    @patch('renderspec.distloader.get_dist_templates_path')
+    def test_dist_templates(self, mock_dt_path):
+        base_txt = ('Line before block\n'
+                    '{% block footest %}{% endblock %}\n'
+                    'Line after block\n')
+        dt_txt = ('{% extends ".spec" %}'
+                  '{% block footest %}'
+                  'foo block\n'
+                  'macro: {{ py2pkg("test") }}\n'
+                  '{% endblock %}')
+        expected_out = ('Line before block\n'
+                        'foo block\n'
+                        'macro: python-test\n'
+                        'Line after block')
+        tmpdir = tempfile.mkdtemp(prefix='renderspec-test_')
+        try:
+            # create .spec template
+            base_path = os.path.join(tmpdir, 'foo.spec.j2')
+            with open(base_path, 'w+') as f:
+                f.write(base_txt)
+            # create custom dist template
+            dt_dir = os.path.join(tmpdir, 'dist-templates')
+            os.mkdir(dt_dir)
+            dt_path = os.path.join(dt_dir, 'loldistro.spec.j2')
+            with open(dt_path, 'w+') as f:
+                f.write(dt_txt)
+            # mock this to use testing dist-tempaltes folder
+            mock_dt_path.return_value = dt_dir
+
+            out = renderspec.generate_spec('loldistro', {}, {}, base_path)
+            self.assertEqual(out, expected_out)
+        finally:
+            shutil.rmtree(tmpdir)
+
+
 if __name__ == '__main__':
     unittest.main()