Fix #1356 -- Allow to override config file settings with env vars

doc/admin/config.rst

@@ -23,6 +23,14 @@ The config file may contain the following sections (all settings are optional an
 default values). We suggest that you start from the examples given in one of the
 installation tutorials.
 
+.. note::
+
+    The configuration file is the recommended way to configure pretix. However, you can
+    also set them through environment variables. In this case, the syntax is
+    ``PRETIX_SECTION_CONFIG``. For example, to configure the setting ``password_reset``
+    from the ``[pretix]`` section, set ``PRETIX_PRETIX_PASSWORD_RESET=off`` in your
+    environment.
+
 pretix settings
 ---------------
 

src/pretix/helpers/config.py

@@ -0,0 +1,43 @@
+import os
+import re
+from configparser import _UNSET
+
+
+class EnvOrParserConfig:
+    def __init__(self, configparser):
+        self.cp = configparser
+
+    def _envkey(self, section, option):
+        section = re.sub('[^a-zA-Z0-9]', '_', section.upper())
+        option = re.sub('[^a-zA-Z0-9]', '_', option.upper())
+        return f'PRETIX_{section}_{option}'
+
+    def get(self, section, option, *, raw=False, vars=None, fallback=_UNSET):
+        if self._envkey(section, option) in os.environ:
+            return os.environ[self._envkey(section, option)]
+        return self.cp.get(section, option, raw=raw, vars=vars, fallback=fallback)
+
+    def getint(self, section, option, *, raw=False, vars=None, fallback=_UNSET):
+        if self._envkey(section, option) in os.environ:
+            return int(os.environ[self._envkey(section, option)])
+        return self.cp.getint(section, option, raw=raw, vars=vars, fallback=fallback)
+
+    def getfloat(self, section, option, *, raw=False, vars=None, fallback=_UNSET):
+        if self._envkey(section, option) in os.environ:
+            return float(os.environ[self._envkey(section, option)])
+        return self.cp.getfloat(section, option, raw=raw, vars=vars, fallback=fallback)
+
+    def getboolean(self, section, option, *, raw=False, vars=None, fallback=_UNSET):
+        if self._envkey(section, option) in os.environ:
+            return self.cp._convert_to_boolean(os.environ[self._envkey(section, option)])
+        return self.cp.getboolean(section, option, raw=raw, vars=vars, fallback=fallback)
+
+    def has_section(self, section):
+        if any(k.startswith(self._envkey(section, '')) for k in os.environ):
+            return True
+        return self.cp.has_section(section)
+
+    def has_option(self, section, option):
+        if self._envkey(section, option) in os.environ:
+            return True
+        return self.cp.has_option(section, option)

src/pretix/settings.py

@@ -11,16 +11,19 @@ from pkg_resources import iter_entry_points
 from pycountry import currencies
 
 from . import __version__
+from .helpers.config import EnvOrParserConfig
+
 
 from django.contrib.messages import constants as messages  # NOQA
 from django.utils.translation import gettext_lazy as _  # NOQA
 
-config = configparser.RawConfigParser()
+_config = configparser.RawConfigParser()
 if 'PRETIX_CONFIG_FILE' in os.environ:
-    config.read_file(open(os.environ.get('PRETIX_CONFIG_FILE'), encoding='utf-8'))
+    _config.read_file(open(os.environ.get('PRETIX_CONFIG_FILE'), encoding='utf-8'))
 else:
-    config.read(['/etc/pretix/pretix.cfg', os.path.expanduser('~/.pretix.cfg'), 'pretix.cfg'],
+    _config.read(['/etc/pretix/pretix.cfg', os.path.expanduser('~/.pretix.cfg'), 'pretix.cfg'],
-                encoding='utf-8')
+                 encoding='utf-8')
+config = EnvOrParserConfig(_config)
 
 CONFIG_FILE = config
 BASE_DIR = os.path.dirname(os.path.dirname(__file__))