feat: fully readable configuration from environment

docs/configuration.rst

@@ -65,6 +65,8 @@ will try to read value from ``SECRET`` environment variable. In case if the requ
 
 will eventually lead ``key`` option in section ``section1`` to be set to the value of ``HOME`` environment variable (if available).
 
+Moreover, configuration can be read from environment variables directly by following the same naming convention, e.g. in the example above, one can have environment variable named ``section1:key`` (e.g. ``section1:key=$HOME``) and it will be substituted to the configuration with the highest priority.
+
 There is also additional subcommand which will allow to validate configuration and print found errors. In order to do so, run ``service-config-validate`` subcommand, e.g.:
 
 .. code-block:: shell

src/ahriman/core/configuration/configuration.py

@@ -19,6 +19,7 @@
 #
 # pylint: disable=too-many-public-methods
 import configparser
+import os
 import shlex
 import sys
 
@@ -164,6 +165,7 @@ class Configuration(configparser.RawConfigParser):
         """
         configuration = cls()
         configuration.load(path)
+        configuration.load_environment()
         configuration.merge_sections(repository_id)
         return configuration
 
@@ -288,6 +290,16 @@ class Configuration(configparser.RawConfigParser):
         self.read(self.path)
         self.load_includes()  # load includes
 
+    def load_environment(self) -> None:
+        """
+        load environment variables into configuration
+        """
+        for name, value in os.environ.items():
+            if ":" not in name:
+                continue
+            section, key = name.rsplit(":", maxsplit=1)
+            self.set_option(section, key, value)
+
     def load_includes(self, path: Path | None = None) -> None:
         """
         load configuration includes from specified path
@@ -356,11 +368,16 @@ class Configuration(configparser.RawConfigParser):
         """
         reload configuration if possible or raise exception otherwise
         """
+        # get current properties and validate input
         path, repository_id = self.check_loaded()
-        for section in self.sections():  # clear current content
+
+        # clear current content
+        for section in self.sections():
             self.remove_section(section)
-        self.load(path)
-        self.merge_sections(repository_id)
+
+        # create another instance and copy values from there
+        instance = self.from_path(path, repository_id)
+        self.copy_from(instance)
 
     def set_option(self, section: str, option: str, value: str) -> None:
         """

tests/ahriman/core/configuration/test_configuration.py

@@ -1,8 +1,8 @@
 import configparser
-from io import StringIO
-
 import pytest
+import os
 
+from io import StringIO
 from pathlib import Path
 from pytest_mock import MockerFixture
 from unittest.mock import call as MockCall
@@ -42,12 +42,16 @@ def test_from_path(repository_id: RepositoryId, mocker: MockerFixture) -> None:
     mocker.patch("ahriman.core.configuration.Configuration.get", return_value="ahriman.ini.d")
     read_mock = mocker.patch("ahriman.core.configuration.Configuration.read")
     load_includes_mock = mocker.patch("ahriman.core.configuration.Configuration.load_includes")
+    merge_mock = mocker.patch("ahriman.core.configuration.Configuration.merge_sections")
+    environment_mock = mocker.patch("ahriman.core.configuration.Configuration.load_environment")
     path = Path("path")
 
     configuration = Configuration.from_path(path, repository_id)
     assert configuration.path == path
     read_mock.assert_called_once_with(path)
     load_includes_mock.assert_called_once_with()
+    merge_mock.assert_called_once_with(repository_id)
+    environment_mock.assert_called_once_with()
 
 
 def test_from_path_file_missing(repository_id: RepositoryId, mocker: MockerFixture) -> None:
@@ -324,6 +328,18 @@ def test_gettype_from_section_no_section(configuration: Configuration) -> None:
         configuration.gettype("rsync:x86_64", configuration.repository_id)
 
 
+def test_load_environment(configuration: Configuration) -> None:
+    """
+    must load environment variables
+    """
+    os.environ["section:key"] = "value1"
+    os.environ["section:identifier:key"] = "value2"
+
+    configuration.load_environment()
+    assert configuration.get("section", "key") == "value1"
+    assert configuration.get("section:identifier", "key") == "value2"
+
+
 def test_load_includes(mocker: MockerFixture) -> None:
     """
     must load includes
@@ -444,10 +460,12 @@ def test_reload(configuration: Configuration, mocker: MockerFixture) -> None:
     """
     load_mock = mocker.patch("ahriman.core.configuration.Configuration.load")
     merge_mock = mocker.patch("ahriman.core.configuration.Configuration.merge_sections")
+    environment_mock = mocker.patch("ahriman.core.configuration.Configuration.load_environment")
 
     configuration.reload()
     load_mock.assert_called_once_with(configuration.path)
     merge_mock.assert_called_once_with(configuration.repository_id)
+    environment_mock.assert_called_once_with()
 
 
 def test_reload_clear(configuration: Configuration, mocker: MockerFixture) -> None: