675 extended env variable interpolation

pywps/configuration.py

@@ -27,6 +27,36 @@
 wps_strict = True
 
 
+class EnvInterpolation(configparser.BasicInterpolation):
+    """
+    Configuration parser class to allow env variable interpolation.
+
+    With this interpolator it is possible to use env variables as
+    part of the values in an cfg file.
+
+    Example (given an env variable HOSTNAME=localhost):
+
+    [server]
+    url = http://${HOSTNAME}/wps
+
+
+    ==> http://localhost/wps
+
+
+    This code is an adaption from the configuation parsing in the pycsw
+    project.
+    See also
+    - https://github.com/geopython/pycsw/blob/3.0.0-alpha3/pycsw/core/util.py
+    - https://stackoverflow.com/a/49529659
+
+    """
+
+    def before_get(self, parser, section, option, value, defaults):
+        """Expand env variables when returning values."""
+        value = super().before_get(parser, section, option, value, defaults)
+        return os.path.expandvars(value)
+
+
 def get_config_value(section, option, default_value=''):
     """Get desired value from  configuration files
 
@@ -67,7 +97,7 @@ def load_configuration(cfgfiles=None):
     global CONFIG
 
     LOGGER.info('loading configuration')
-    CONFIG = configparser.ConfigParser(os.environ)
+    CONFIG = configparser.ConfigParser(os.environ, interpolation=EnvInterpolation())
 
     LOGGER.debug('setting default values')
     CONFIG.add_section('server')

tests/__init__.py

@@ -13,6 +13,7 @@
 import pywps.configuration as config
 
 from tests import test_capabilities
+from tests import test_configuration
 from tests import test_describe
 from tests import test_execute
 from tests import test_exceptions
@@ -76,6 +77,7 @@ def load_tests(loader=None, tests=None, pattern=None):
 
     return unittest.TestSuite([
         test_capabilities.load_tests(),
+        test_configuration.load_tests(),
         test_execute.load_tests(),
         test_describe.load_tests(),
         test_inout.load_tests(),

tests/test_configuration.py

@@ -0,0 +1,49 @@
+##################################################################
+# Copyright 2018 Open Source Geospatial Foundation and others    #
+# licensed under MIT, Please consult LICENSE.txt for details     #
+##################################################################
+
+"""Tests for the configuration."""
+
+import os
+import unittest
+
+from pywps import configuration
+
+
+class TestEnvInterpolation(unittest.TestCase):
+    """Test cases for env variable interpolation within the configuration."""
+
+    def test_expand_user(self):
+        """Ensure we can parse a value with the $USER entry."""
+        user = os.environ.get("USER")
+        configuration.CONFIG.read_string("[envinterpolationsection]\nuser=$USER")
+        assert user == configuration.CONFIG["envinterpolationsection"]["user"]
+
+    def test_expand_user_with_some_text(self):
+        """Ensure we can parse a value with the $USER entry and some more text."""
+        user = os.environ.get("USER")
+        new_user = "new_" + user
+        configuration.CONFIG.read_string("[envinterpolationsection]\nuser=new_${USER}")
+        assert new_user == configuration.CONFIG["envinterpolationsection"]["user"]
+
+    def test_dont_expand_value_without_env_variable(self):
+        """
+        Ensure we don't expand values that are no env variables.
+
+        Could be an important case for existing config keys that need to
+        contain the $symbol.
+        """
+        key = "$example_key_that_hopefully_will_never_be_a_real_env_variable"
+        configuration.CONFIG.read_string("[envinterpolationsection]\nuser=" + key)
+        assert key == configuration.CONFIG["envinterpolationsection"]["user"]
+
+
+def load_tests(loader=None, tests=None, pattern=None):
+    """Load the tests and return the test suite for this file."""
+    if not loader:
+        loader = unittest.TestLoader()
+    suite_list = [
+        loader.loadTestsFromTestCase(TestEnvInterpolation),
+    ]
+    return unittest.TestSuite(suite_list)