adds Config

src/ploomber/config.py

@@ -0,0 +1,59 @@
+import abc
+from collections.abc import Mapping
+
+import yaml
+
+
+class Config(abc.ABC):
+    def __init__(self):
+        # resolve home directory
+        path = self.path()
+
+        if not path.exists():
+            defaults = self._get_data()
+            path.write_text(yaml.dump(defaults))
+            self._set_data(defaults)
+        else:
+            text = path.read_text()
+
+            try:
+                content = yaml.safe_load(text)
+                loaded = True
+            except Exception:
+                # NOTE: show warning?
+                loaded = False
+                content = self._get_data()
+
+            if loaded and not isinstance(content, Mapping):
+                # NOTE: show warning?
+                content = self._get_data()
+
+            self._set_data(content)
+
+    # TODO: delete, only here for compatibility
+    def read(self):
+        return self._get_data()
+
+    def _get_data(self):
+        return {key: getattr(self, key) for key in self.__annotations__}
+
+    def _set_data(self, data):
+        for key in self.__annotations__:
+            if key in data:
+                setattr(self, key, data[key])
+
+    def _write(self):
+        path = self.path()
+        data = self._get_data()
+        path.write_text(yaml.dump(data))
+
+    def __setattr__(self, name, value):
+        if name not in self.__annotations__:
+            raise ValueError(f'{name} not a valid field')
+        else:
+            super().__setattr__(name, value)
+            self._write()
+
+    @abc.abstractclassmethod
+    def path(cls):
+        pass

tests/test_config.py

@@ -0,0 +1,80 @@
+from pathlib import Path
+
+import pytest
+import yaml
+
+from ploomber.config import Config
+
+
+class MyConfig(Config):
+    number: int = 42
+    string: str = 'value'
+
+    def path(self):
+        return Path('myconfig.yaml')
+
+
+def test_stores_defaults(tmp_directory):
+    MyConfig()
+
+    content = yaml.safe_load(Path('myconfig.yaml').read_text())
+
+    assert content == {'number': 42, 'string': 'value'}
+
+
+def test_reads_existing(tmp_directory):
+    path = Path('myconfig.yaml')
+    path.write_text(yaml.dump({'number': 100}))
+
+    cfg = MyConfig()
+
+    assert cfg.number == 100
+    assert cfg.string == 'value'
+
+
+def test_ignores_extra(tmp_directory):
+    path = Path('myconfig.yaml')
+    path.write_text(
+        yaml.dump({
+            'number': 200,
+            'string': 'another',
+            'unknown': 2000,
+        }))
+
+    cfg = MyConfig()
+
+    assert cfg.number == 200
+    assert cfg.string == 'another'
+
+
+def test_stores_on_update(tmp_directory):
+    cfg = MyConfig()
+
+    cfg.number = 500
+
+    content = yaml.safe_load(Path('myconfig.yaml').read_text())
+
+    assert content == {'number': 500, 'string': 'value'}
+
+
+def test_uses_default_if_missing(tmp_directory):
+    path = Path('myconfig.yaml')
+    path.write_text(yaml.dump({'number': 100}))
+
+    cfg = MyConfig()
+
+    assert cfg.number == 100
+    assert cfg.string == 'value'
+
+
+@pytest.mark.parametrize('content', ['not yaml', '[[]'])
+def test_uses_defaults_if_corrupted(tmp_directory, content):
+    path = Path('myconfig.yaml')
+    path.write_text(content)
+
+    cfg = MyConfig()
+    content = yaml.safe_load(Path('myconfig.yaml').read_text())
+
+    assert cfg.number == 42
+    assert cfg.string == 'value'
+    assert content == {'number': 42, 'string': 'value'}