Support custom jinja2 filters.

This uses the plugin framework to add filter plugins.
The previously hardcoded core filters are defined using the plugin
framework now.

examples/playbooks/custom_filters.yml

+---
+
+- name: Demonstrate custom jinja2 filters
+  hosts: all
+  tasks:
+  - action: template src=templates/custom-filters.j2 dest=/tmp/custom-filters.txt

examples/playbooks/filter_plugins/custom_plugins.py

+# (c) 2012, Jeroen Hoekx <jeroen@hoekx.be>
+#
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+
+class FilterModule(object):
+    ''' Custom filters are loaded by FilterModule objects '''
+
+    def filters(self):
+        ''' FilterModule objects return a dict mapping filter names to
+            filter functions. '''
+        return {
+            'generate_answer': self.generate_answer,
+        }
+
+    def generate_answer(self, value):
+        return '42'

examples/playbooks/templates/custom-filters.j2

+1 + 1 = {{ '1+1' | generate_answer }}

lib/ansible/constants.py

@@ -93,6 +93,7 @@ DEFAULT_CALLBACK_PLUGIN_PATH   = shell_expand_path(get_config(p, DEFAULTS, 'call
 DEFAULT_CONNECTION_PLUGIN_PATH = shell_expand_path(get_config(p, DEFAULTS, 'connection_plugins', None, '/usr/share/ansible_plugins/connection_plugins'))
 DEFAULT_LOOKUP_PLUGIN_PATH     = shell_expand_path(get_config(p, DEFAULTS, 'lookup_plugins',     None, '/usr/share/ansible_plugins/lookup_plugins'))
 DEFAULT_VARS_PLUGIN_PATH     = shell_expand_path(get_config(p, DEFAULTS, 'vars_plugins',     None, '/usr/share/ansible_plugins/vars_plugins'))
+DEFAULT_FILTER_PLUGIN_PATH     = shell_expand_path(get_config(p, DEFAULTS, 'filter_plugins',     None, '/usr/share/ansible_plugins/filter_plugins'))
 
 # non-configurable things
 DEFAULT_SUDO_PASS         = None

lib/ansible/runner/filter_plugins/core.py

+# (c) 2012, Jeroen Hoekx <jeroen@hoekx.be>
+#
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+
+import json
+import yaml
+
+class FilterModule(object):
+    ''' Ansible core jinja2 filters '''
+
+    def filters(self):
+        return {
+            'to_json': json.dumps,
+            'from_json': json.loads,
+            'to_yaml': yaml.dump,
+            'from_yaml': yaml.load,
+        }
+    

lib/ansible/utils/plugins.py

@@ -95,3 +95,4 @@ callback_loader   = PluginLoader('CallbackModule', 'ansible.callback_plugins',
 connection_loader = PluginLoader('Connection',     'ansible.runner.connection_plugins', C.DEFAULT_CONNECTION_PLUGIN_PATH, 'connection_plugins', aliases={'paramiko': 'paramiko_ssh'})
 lookup_loader     = PluginLoader('LookupModule',   'ansible.runner.lookup_plugins',     C.DEFAULT_LOOKUP_PLUGIN_PATH,     'lookup_plugins')
 vars_loader       = PluginLoader('VarsModule',     'ansible.inventory.vars_plugins',    C.DEFAULT_VARS_PLUGIN_PATH,       'vars_plugins')
+filter_loader     = PluginLoader('FilterModule',   'ansible.runner.filter_plugins',     C.DEFAULT_FILTER_PLUGIN_PATH,     'filter_plugins')

lib/ansible/utils/template.py

@@ -221,10 +221,11 @@ def template_from_file(basedir, path, vars):
     realpath = utils.path_dwim(basedir, path)
     loader=jinja2.FileSystemLoader([basedir,os.path.dirname(realpath)])
     environment = jinja2.Environment(loader=loader, trim_blocks=True)
-    environment.filters['to_json'] = json.dumps
-    environment.filters['from_json'] = json.loads
-    environment.filters['to_yaml'] = yaml.dump
-    environment.filters['from_yaml'] = yaml.load
+    for filter_plugin in utils.plugins.filter_loader.all():
+        filters = filter_plugin.filters()
+        if not isinstance(filters, dict):
+            raise errors.AnsibleError("FilterModule.filters should return a dict.")
+        environment.filters.update(filters)
     try:
         data = codecs.open(realpath, encoding="utf8").read()
     except UnicodeDecodeError: