Support UVICORN_APP

Uvicorn 0.24.0 adds support for setting the app instance with the
environment variable `UVICORN_APP`. inboard already has an environment
variable for this purpose, `APP_MODULE`.

This commit will add support for `UVICORN_APP`. Either `APP_MODULE` or
`UVICORN_APP` can be used to set the app module for inboard, with
precendence given to `APP_MODULE` for backward compatibility.

https://github.com/encode/uvicorn/releases/tag/0.24.0
encode/uvicorn#2106

docs/environment.md

@@ -20,11 +20,11 @@ ENV APP_MODULE="package.custom.module:api" WORKERS_PER_CORE="2"
 
 ## General
 
-`APP_MODULE`
+`APP_MODULE`/`UVICORN_APP`
 
 -   Python module with app instance.
 -   Default: The appropriate app module from inboard.
--   Custom: For a module at `/app/package/custom/module.py` and app instance object `api`, `APP_MODULE="package.custom.module:api"`
+-   Custom: For a module at `/app/package/custom/module.py` and app instance object `api`, either `APP_MODULE` (like `APP_MODULE="package.custom.module:api"`) or `UVICORN_APP` (like `UVICORN_APP="package.custom.module:api"`, _new in inboard 0.62_)
 
     !!!example "Example of a custom FastAPI app module"
 
@@ -188,6 +188,8 @@ ENV APP_MODULE="package.custom.module:api" WORKERS_PER_CORE="2"
 
     These settings are mostly used for local development.
 
+    [Uvicorn supports environment variables named with the `UVICORN_` prefix](https://www.uvicorn.org/settings/) (via the [Click `auto_envvar_prefix` feature](https://click.palletsprojects.com/en/7.x/options/#dynamic-defaults-for-prompts)), but these environment variables are only read when running from the CLI. inboard runs Uvicorn programmatically with `uvicorn.run()` instead of running with the CLI, so most of these variables will not apply. The exception is `UVICORN_APP`, as explained in the [general section](#general).
+
 `WITH_RELOAD`
 
 -   Configure the [Uvicorn auto-reload setting](https://www.uvicorn.org/settings/).
@@ -249,6 +251,11 @@ ENV APP_MODULE="package.custom.module:api" WORKERS_PER_CORE="2"
         - `uvicorn.run` equivalent: `reload_includes`
         - Uvicorn CLI equivalent: `--reload-include`
 
+`UVICORN_APP` _(new in inboard 0.62)_
+
+-   `UVICORN_APP` can be used interchangeably with `APP_MODULE`.
+-   See the [general section](#general) for further details.
+
 `UVICORN_CONFIG_OPTIONS` _(advanced usage, new in inboard 0.11)_
 
 -   JSON-formatted string containing arguments to pass directly to Uvicorn.

inboard/start.py

@@ -38,7 +38,7 @@ def run_pre_start_script(logger: logging.Logger = logging.getLogger()) -> str:
 def set_app_module(logger: logging.Logger = logging.getLogger()) -> str:
     """Set the name of the Python module with the app instance to run."""
     try:
-        app_module = os.getenv("APP_MODULE")
+        app_module = os.getenv("APP_MODULE") or os.getenv("UVICORN_APP")
         if not app_module:
             raise ValueError("Please set the APP_MODULE environment variable")
         if not importlib.util.find_spec((module := app_module.split(sep=":")[0])):

tests/test_start.py

@@ -128,17 +128,19 @@ def test_set_app_module(
         assert mocker.call(f"App module set to inboard.app.main_{module}:app.")
 
     @pytest.mark.parametrize("module", ("base", "fastapi", "starlette"))
+    @pytest.mark.parametrize("module_variable_name", ("APP_MODULE", "UVICORN_APP"))
     def test_set_app_module_custom(
         self,
         app_module_tmp_path: Path,
         module: str,
+        module_variable_name: str,
         mocker: MockerFixture,
         monkeypatch: pytest.MonkeyPatch,
     ) -> None:
         """Test `start.set_app_module` with custom module path."""
         logger = mocker.patch.object(logging, "root", autospec=True)
         monkeypatch.syspath_prepend(app_module_tmp_path)
-        monkeypatch.setenv("APP_MODULE", f"tmp_app.main_{module}:app")
+        monkeypatch.setenv(module_variable_name, f"tmp_app.main_{module}:app")
         start.set_app_module(logger=logger)
         assert mocker.call(f"App module set to tmp_app.main_{module}:app.")