Add support for themes to define their own defaults

pelican/settings.py

@@ -524,6 +524,22 @@ def configure_settings(settings):
             raise Exception("Could not find the theme %s"
                             % settings['THEME'])
 
+    theme_config = os.path.join(settings['THEME'], 'pelicanconf.py')
+    if os.path.isfile(theme_config):
+        preserved = {}
+        logger.debug('Theme provides a config `%s`', theme_config)
+        # preserve variables that are dynamically calculated in read_settings()
+        for p in ['PATH', 'OUTPUT_PATH', 'THEME', 'CACHE_PATH', 'PLUGIN_PATHS']:
+            if settings.get(p) is not None:
+                preserved[p] = settings.get(p)
+        settings.pop('THEME') # avoid recursion
+        settings = read_settings(theme_config, settings)
+        # restore them back to look like we did not calculate them again
+        for p in ['PATH', 'OUTPUT_PATH', 'THEME', 'CACHE_PATH', 'PLUGIN_PATHS']:
+            if preserved.get(p) is not None:
+                settings[p] = preserved.pop(p)
+
+
     # make paths selected for writing absolute if necessary
     settings['WRITE_SELECTED'] = [
         os.path.abspath(path) for path in

pelican/tests/test_settings.py

@@ -6,14 +6,12 @@ import os
 from os.path import abspath, dirname, join
 from sys import platform
 
-
 from pelican.settings import (DEFAULT_CONFIG, DEFAULT_THEME,
                               _printf_s_to_format_field,
                               configure_settings, handle_deprecated_settings,
                               read_settings)
 from pelican.tests.support import unittest
 
-
 class TestSettingsConfiguration(unittest.TestCase):
     """Provided a file, it should read it, replace the default values,
     append new values to the settings (if any), and apply basic settings
@@ -66,6 +64,18 @@ class TestSettingsConfiguration(unittest.TestCase):
         new_settings = read_settings(default_conf)
         self.assertNotEqual(new_settings['SITEURL'], settings['SITEURL'])
 
+    def test_theme_settings_applied(self):
+        # Make sure that the results from loading theme's config do not
+        # affect the previously defined system configuration
+        self.PATH = abspath(dirname(__file__))
+        default_conf = join(self.PATH, 'default_conf.py')
+        expected = copy.deepcopy(self.settings)
+        expected['THEME'] = os.path.join(self.PATH, 'themes/custom')
+        expected['CUSTOM_THEME_SETTING'] = 'test'
+        settings = read_settings(default_conf, { 'THEME': 'themes/custom' } )
+        self.maxDiff = None
+        self.assertDictEqual(settings, expected)
+
     def test_defaults_not_overwritten(self):
         # This assumes 'SITENAME': 'A Pelican Blog'
         settings = read_settings(None)

pelican/tests/themes/custom/pelicanconf.py

@@ -0,0 +1,3 @@
+CUSTOM_THEME_SETTING = 'test'
+PATH = 'a path'
+AUTHOR = 'Test Suite'