Add a config object

- add the following file:
  + src/urban_meal_delivery/_config.py
- a config module is created holding two sets of configurations:
  + production => against the real database
  + testing => against a database with test data
- the module is "protected" (i.e., underscore) and imported at the
  top level via a proxy-like object `config` that detects in which of
  the two environments the package is being run

.gitignore

@@ -1,4 +1,5 @@
 .cache/
 *.egg-info/
+.env
 .python-version
 .venv/

poetry.lock

@@ -804,6 +804,17 @@ pytest = ">=4.6"
 [package.extras]
 testing = ["fields", "hunter", "process-tests (2.0.2)", "six", "pytest-xdist", "virtualenv"]
 
+[[package]]
+category = "main"
+description = "Add .env support to your django/flask apps in development and deployments"
+name = "python-dotenv"
+optional = false
+python-versions = "*"
+version = "0.14.0"
+
+[package.extras]
+cli = ["click (>=5.0)"]
+
 [[package]]
 category = "dev"
 description = "World timezone definitions, modern and historical"
@@ -1140,7 +1151,7 @@ optional = ["pygments", "colorama"]
 tests = ["pytest", "pytest-cov", "codecov", "scikit-build", "cmake", "ninja", "pybind11"]
 
 [metadata]
-content-hash = "beb356287b912e1ce67c5997bd4d683dbc424ee24660a93d8f1fb4e511972762"
+content-hash = "862a0bc650dab485af541f185ed3c1e86a8947e7518c8fbcacfd19d5b8055af5"
 lock-version = "1.0"
 python-versions = "^3.8"
 
@@ -1526,6 +1537,10 @@ pytest-cov = [
     {file = "pytest-cov-2.10.0.tar.gz", hash = "sha256:1a629dc9f48e53512fcbfda6b07de490c374b0c83c55ff7a1720b3fccff0ac87"},
     {file = "pytest_cov-2.10.0-py2.py3-none-any.whl", hash = "sha256:6e6d18092dce6fad667cd7020deed816f858ad3b49d5b5e2b1cc1c97a4dba65c"},
 ]
+python-dotenv = [
+    {file = "python-dotenv-0.14.0.tar.gz", hash = "sha256:8c10c99a1b25d9a68058a1ad6f90381a62ba68230ca93966882a4dbc3bc9c33d"},
+    {file = "python_dotenv-0.14.0-py2.py3-none-any.whl", hash = "sha256:c10863aee750ad720f4f43436565e4c1698798d763b63234fb5021b6c616e423"},
+]
 pytz = [
     {file = "pytz-2020.1-py2.py3-none-any.whl", hash = "sha256:a494d53b6d39c3c6e44c3bec237336e14305e4f29bbf800b599253057fbb79ed"},
     {file = "pytz-2020.1.tar.gz", hash = "sha256:c35965d010ce31b23eeb663ed3cc8c906275d6be1a34393a1d73a41febf4a048"},

pyproject.toml

@@ -28,6 +28,7 @@ repository = "https://github.com/webartifex/urban-meal-delivery"
 python = "^3.8"
 
 click = "^7.1.2"
+python-dotenv = "^0.14.0"
 
 [tool.poetry.dev-dependencies]
 # Task Runners

setup.cfg

@@ -109,6 +109,11 @@ per-file-ignores =
         WPS213,
         # No overuse of string constants (e.g., '--version').
         WPS226,
+    src/urban_meal_delivery/_config.py:
+        # Allow upper case class variables within classes.
+        WPS115,
+        # Numbers are normal in config files.
+        WPS432,
     tests/*.py:
         # Type annotations are not strictly enforced.
         ANN0, ANN2,
@@ -135,10 +140,10 @@ show-source = true
 # wemake-python-styleguide's settings
 # ===================================
 allowed-domain-names =
+    obj,
     param,
     result,
     value,
-min-name-length = 3
 max-name-length = 40
 # darglint
 strictness = long
@@ -186,7 +191,13 @@ single_line_exclusions = typing
 [mypy]
 cache_dir = .cache/mypy
 
-[mypy-nox.*,packaging,pytest]
+[mypy-dotenv]
+ignore_missing_imports = true
+[mypy-nox.*]
+ignore_missing_imports = true
+[mypy-packaging]
+ignore_missing_imports = true
+[mypy-pytest]
 ignore_missing_imports = true
 
 

src/urban_meal_delivery/__init__.py

@@ -6,8 +6,11 @@ Example:
     True
 """
 
+import os as _os
 from importlib import metadata as _metadata
 
+from urban_meal_delivery import _config  # noqa:WPS450
+
 
 try:
     _pkg_info = _metadata.metadata(__name__)
@@ -21,3 +24,7 @@ else:
     __author__ = _pkg_info['author']
     __pkg_name__ = _pkg_info['name']
     __version__ = _pkg_info['version']
+
+
+# Little Hack: "Overwrites" the config module so that the environment is already set.
+config = _config.get_config('testing' if _os.getenv('TESTING') else 'production')

src/urban_meal_delivery/_config.py

@@ -0,0 +1,87 @@
+"""Provide package-wide configuration.
+
+This module is "protected" so that it is only used
+via the `config` proxy at the package's top level.
+
+That already loads the correct configuration
+depending on the current environment.
+"""
+
+import datetime
+import os
+import warnings
+
+import dotenv
+
+
+dotenv.load_dotenv()
+
+
+class Config:
+    """Configuration that applies in all situations."""
+
+    # pylint:disable=too-few-public-methods
+
+    CUTOFF_DAY = datetime.datetime(2017, 2, 1)
+
+    # If a scheduled pre-order is made within this
+    # time horizon, we treat it as an ad-hoc order.
+    QUASI_AD_HOC_LIMIT = datetime.timedelta(minutes=45)
+
+    DATABASE_URI = os.getenv('DATABASE_URI')
+
+    # The PostgreSQL schema that holds the tables with the original data.
+    ORIGINAL_SCHEMA = os.getenv('ORIGINAL_SCHEMA') or 'public'
+
+    # The PostgreSQL schema that holds the tables with the cleaned data.
+    CLEAN_SCHEMA = os.getenv('CLEAN_SCHEMA') or 'clean'
+
+    def __repr__(self) -> str:
+        """Non-literal text representation."""
+        return '<configuration>'
+
+
+class ProductionConfig(Config):
+    """Configuration for the real dataset."""
+
+    # pylint:disable=too-few-public-methods
+
+    TESTING = False
+
+
+class TestingConfig(Config):
+    """Configuration for the test suite."""
+
+    # pylint:disable=too-few-public-methods
+
+    TESTING = True
+
+    DATABASE_URI = os.getenv('DATABASE_URI_TESTING') or Config.DATABASE_URI
+    CLEAN_SCHEMA = os.getenv('CLEAN_SCHEMA_TESTING') or Config.CLEAN_SCHEMA
+
+
+def get_config(env: str = 'production') -> Config:
+    """Get the configuration for the package.
+
+    Args:
+        env: either 'production' or 'testing'; defaults to the first
+
+    Returns:
+        config: a namespace with all configurations
+
+    Raises:
+        ValueError: if `env` is not as specified
+    """  # noqa:DAR203
+    config: Config
+    if env.strip().lower() == 'production':
+        config = ProductionConfig()
+    elif env.strip().lower() == 'testing':
+        config = TestingConfig()
+    else:
+        raise ValueError("Must be either 'production' or 'testing'")
+
+    # Without a PostgreSQL database the package cannot work.
+    if config.DATABASE_URI is None:
+        warnings.warn('Bad configurartion: no DATABASE_URI set in the environment')
+
+    return config

tests/test_config.py

@@ -0,0 +1,45 @@
+"""Test the package's configuration module."""
+
+import pytest
+
+from urban_meal_delivery import _config as config_mod  # noqa:WPS450
+
+
+envs = ['production', 'testing']
+
+
+@pytest.mark.parametrize('env', envs)
+def test_config_repr(env):
+    """Config objects have the text representation '<configuration>'."""
+    config = config_mod.get_config(env)
+
+    assert str(config) == '<configuration>'
+
+
+def test_invalid_config():
+    """There are only 'production' and 'testing' configurations."""
+    with pytest.raises(ValueError, match="'production' or 'testing'"):
+        config_mod.get_config('invalid')
+
+
+@pytest.mark.parametrize('env', envs)
+def test_database_uri_set(env, monkeypatch):
+    """Package does NOT emit warning if DATABASE_URI is set."""
+    uri = 'postgresql://user:password@localhost/db'
+    monkeypatch.setattr(config_mod.ProductionConfig, 'DATABASE_URI', uri)
+    monkeypatch.setattr(config_mod.TestingConfig, 'DATABASE_URI', uri)
+
+    with pytest.warns(None) as record:
+        config_mod.get_config(env)
+
+    assert len(record) == 0  # noqa:WPS441,WPS507
+
+
+@pytest.mark.parametrize('env', envs)
+def test_no_database_uri_set(env, monkeypatch):
+    """Package does not work without DATABASE_URI set in the environment."""
+    monkeypatch.setattr(config_mod.ProductionConfig, 'DATABASE_URI', None)
+    monkeypatch.setattr(config_mod.TestingConfig, 'DATABASE_URI', None)
+
+    with pytest.warns(UserWarning, match='no DATABASE_URI'):
+        config_mod.get_config(env)