feat: Allow configuration of config envvar

README.md

@@ -102,6 +102,21 @@ After modifying the settings to your liking, `podcast-archiver` can be run with
 podcast-archiver --config path/to/config.yaml
 ```
 
+Alternatively (for example, if you're running `podcast-archiver` in Docker), you may point it to the config file using the `PODCAST_ARCHIVER_CONFIG=path/to/config.yaml` environment variable.
+
+### Using environment variables
+
+`podcast-archiver` uses [Pydantic](https://docs.pydantic.dev/latest/usage/settings/#parsing-environment-variable-values) to parse and validate its configuration. You can also prefix all configuration options (as used in the config file) with `PODCAST_ARCHIVER_` and export the results as environment variables to change the behavior, like so:
+
+```bash
+export PODCAST_ARCHIVER_FEEDS='[
+    "http://raumzeit-podcast.de/feed/m4a/",
+    "https://feeds.lagedernation.org/feeds/ldn-mp3.xml"
+]'  # Must be a string of a JSON array
+export PODCAST_ARCHIVER_SLUGIFY_PATHS=true
+export PODCAST_ARCHIVER_VERBOSE=2
+```
+
 ## Excursion: Unicode Normalization in Slugify
 
 The `--slugify` option removes all ambiguous characters from folders and filenames used in the archiving process. The removal includes unicode normalization according to [Compatibility Decomposition](http://unicode.org/reports/tr15/tr15-18.html#Decomposition). What? Yeah, me too. I figured this is best seen in an example, so here's a fictitious episode name, and how it would be translated to an target filename using the Archiver:

podcast_archiver/__main__.py

@@ -21,7 +21,8 @@ def main(argv: Union[list[str], None] = None) -> None:
             Settings.generate_example(args.config_generate)
             sys.exit(0)
 
-        settings = Settings.load_and_merge(args.config, args)
+        settings = Settings.load_from_yaml(args.config)
+        settings.merge_argparser_args(args)
         if not (settings.opml_files or settings.feeds):
             parser.error("Must provide at least one of --feed or --opml")
 

podcast_archiver/config.py

@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import textwrap
+from os import environ
 from pathlib import Path
 from typing import TYPE_CHECKING, Any, Union
 
@@ -106,30 +107,44 @@ def normalize_opml_files(cls, v: Any) -> Path:
 
     @classmethod
     def load_from_yaml(cls, path: Union[Path, None]) -> Settings:
+        target = None
         if path and path.is_file():
-            with path.open("r") as filep:
+            target = path
+        else:
+            target = cls._get_envvar_config_path()
+
+        if target:
+            with target.open("r") as filep:
                 content = safe_load(filep)
             if content:
                 return cls.parse_obj(content)
         return cls()  # type: ignore[call-arg]
 
     @classmethod
-    def load_and_merge(cls, path: Union[Path, None], args: argparse.Namespace):
-        settings = cls.load_from_yaml(path)
-        for name, field in settings.__fields__.items():
+    def _get_envvar_config_path(cls) -> Union[Path, None]:
+        if not (var_value := environ.get(f"{cls.Config.env_prefix}CONFIG")):
+            return None
+
+        if not (env_path := Path(var_value).expanduser()).is_file():
+            raise FileNotFoundError(f"{env_path} does not exist")
+
+        return env_path
+
+    def merge_argparser_args(self, args: argparse.Namespace):
+        for name, field in self.__fields__.items():
             if (args_value := getattr(args, name, None)) is None:
                 continue
 
-            settings_value = getattr(settings, name)
+            settings_value = getattr(self, name)
             if isinstance(settings_value, list) and isinstance(args_value, list):
-                setattr(settings, name, settings_value + args_value)
+                setattr(self, name, settings_value + args_value)
                 continue
 
             if args_value != field.get_default():
-                setattr(settings, name, args_value)
+                setattr(self, name, args_value)
 
-        merged_settings = settings.dict(exclude_defaults=True, exclude_unset=True)
-        return cls.parse_obj(merged_settings)
+        merged_settings = self.dict(exclude_defaults=True, exclude_unset=True)
+        return self.parse_obj(merged_settings)
 
     @classmethod
     def generate_example(cls, path: Path) -> None:

pyproject.toml

@@ -53,6 +53,7 @@ pre-commit = "^3.2.2"
 pytest = "^7.3.1"
 pytest-cov = "^4.0.0"
 pytest-responses = "^0.5.1"
+pytest-env = "^0.8.1"
 
 [tool.ruff]
 line-length = 120
@@ -86,12 +87,19 @@ target-version = ['py39', 'py310', 'py311']
 minversion = "6.0"
 testpaths = ["tests",]
 addopts = "--cov podcast_archiver --cov-report term --no-cov-on-fail"
+env = [
+    "PODCAST_ARCHIVER_CONFIG=",
+]
 
 [tool.coverage.run]
 omit = ["tests/*", "venv/*", ".venv/*"]
 
 [tool.coverage.report]
 precision = 1
+exclude_lines = [
+    "pragma: no cover",
+    "if TYPE_CHECKING:",
+]
 
 [tool.mypy]
 warn_unused_configs = true

tests/test_config.py

@@ -0,0 +1,33 @@
+from pathlib import Path
+
+import pytest
+
+from podcast_archiver.config import Settings
+
+DUMMY_FEED = "http://localhost/feed.rss"
+
+
+def test_load_from_envvar_config_path(tmp_path_cd: Path, monkeypatch):
+    configfile = tmp_path_cd / "configtmp.yaml"
+    configfile.write_text(f"feeds: [{DUMMY_FEED}]")
+
+    monkeypatch.setenv("PODCAST_ARCHIVER_CONFIG", configfile)
+    settings = Settings.load_from_yaml(None)
+
+    assert DUMMY_FEED in settings.feeds
+
+
+def test_load_from_envvar_config_path_nonexistent(monkeypatch):
+    monkeypatch.setenv("PODCAST_ARCHIVER_CONFIG", "nonexistent")
+    with pytest.raises(FileNotFoundError):
+        Settings.load_from_yaml(None)
+
+
+def test_load_from_envvar_config_path_overridden_by_arg(tmp_path_cd: Path, monkeypatch):
+    configfile = tmp_path_cd / "configtmp.yaml"
+    configfile.write_text(f"feeds: [{DUMMY_FEED}]")
+
+    monkeypatch.setenv("PODCAST_ARCHIVER_CONFIG", "nonexistent")
+    settings = Settings.load_from_yaml(configfile)
+
+    assert DUMMY_FEED in settings.feeds