feat: ignore empty env vars (#198)

docs/index.md

@@ -253,6 +253,11 @@ except ValidationError as e:
 
 ## Parsing environment variable values
 
+By default environment variables are parsed verbatim, including if the value is empty. You can choose to
+ignore empty environment variables by setting the `env_ignore_empty` config setting to `True`. This can be
+useful if you would prefer to use the default value for a field rather than an empty value from the
+environment.
+
 For most simple field types (such as `int`, `float`, `str`, etc.), the environment variable value is parsed
 the same way it would be if passed directly to the initialiser (as a string).
 

pydantic_settings/main.py

@@ -24,6 +24,7 @@ class SettingsConfigDict(ConfigDict, total=False):
     env_prefix: str
     env_file: DotenvType | None
     env_file_encoding: str | None
+    env_ignore_empty: bool
     env_nested_delimiter: str | None
     secrets_dir: str | Path | None
 
@@ -53,6 +54,7 @@ class BaseSettings(BaseModel):
             means that the value from `model_config['env_file']` should be used. You can also pass
             `None` to indicate that environment variables should not be loaded from an env file.
         _env_file_encoding: The env file encoding, e.g. `'latin-1'`. Defaults to `None`.
+        _env_ignore_empty: Ignore environment variables where the value is an empty string. Default to `False`.
         _env_nested_delimiter: The nested env values delimiter. Defaults to `None`.
         _secrets_dir: The secret files directory. Defaults to `None`.
     """
@@ -63,6 +65,7 @@ def __init__(
         _env_prefix: str | None = None,
         _env_file: DotenvType | None = ENV_FILE_SENTINEL,
         _env_file_encoding: str | None = None,
+        _env_ignore_empty: bool | None = None,
         _env_nested_delimiter: str | None = None,
         _secrets_dir: str | Path | None = None,
         **values: Any,
@@ -75,6 +78,7 @@ def __init__(
                 _env_prefix=_env_prefix,
                 _env_file=_env_file,
                 _env_file_encoding=_env_file_encoding,
+                _env_ignore_empty=_env_ignore_empty,
                 _env_nested_delimiter=_env_nested_delimiter,
                 _secrets_dir=_secrets_dir,
             )
@@ -111,6 +115,7 @@ def _settings_build_values(
         _env_prefix: str | None = None,
         _env_file: DotenvType | None = None,
         _env_file_encoding: str | None = None,
+        _env_ignore_empty: bool | None = None,
         _env_nested_delimiter: str | None = None,
         _secrets_dir: str | Path | None = None,
     ) -> dict[str, Any]:
@@ -121,6 +126,9 @@ def _settings_build_values(
         env_file_encoding = (
             _env_file_encoding if _env_file_encoding is not None else self.model_config.get('env_file_encoding')
         )
+        env_ignore_empty = (
+            _env_ignore_empty if _env_ignore_empty is not None else self.model_config.get('env_ignore_empty')
+        )
         env_nested_delimiter = (
             _env_nested_delimiter
             if _env_nested_delimiter is not None
@@ -135,6 +143,7 @@ def _settings_build_values(
             case_sensitive=case_sensitive,
             env_prefix=env_prefix,
             env_nested_delimiter=env_nested_delimiter,
+            env_ignore_empty=env_ignore_empty,
         )
         dotenv_settings = DotEnvSettingsSource(
             self.__class__,
@@ -143,6 +152,7 @@ def _settings_build_values(
             case_sensitive=case_sensitive,
             env_prefix=env_prefix,
             env_nested_delimiter=env_nested_delimiter,
+            env_ignore_empty=env_ignore_empty,
         )
 
         file_secret_settings = SecretsSettingsSource(
@@ -171,6 +181,7 @@ def _settings_build_values(
         env_prefix='',
         env_file=None,
         env_file_encoding=None,
+        env_ignore_empty=False,
         env_nested_delimiter=None,
         secrets_dir=None,
         protected_namespaces=('model_', 'settings_'),

pydantic_settings/sources.py

@@ -129,11 +129,18 @@ def __repr__(self) -> str:
 
 class PydanticBaseEnvSettingsSource(PydanticBaseSettingsSource):
     def __init__(
-        self, settings_cls: type[BaseSettings], case_sensitive: bool | None = None, env_prefix: str | None = None
+        self,
+        settings_cls: type[BaseSettings],
+        case_sensitive: bool | None = None,
+        env_prefix: str | None = None,
+        env_ignore_empty: bool | None = None,
     ) -> None:
         super().__init__(settings_cls)
         self.case_sensitive = case_sensitive if case_sensitive is not None else self.config.get('case_sensitive', False)
         self.env_prefix = env_prefix if env_prefix is not None else self.config.get('env_prefix', '')
+        self.env_ignore_empty = (
+            env_ignore_empty if env_ignore_empty is not None else self.config.get('env_ignore_empty', False)
+        )
 
     def _apply_case_sensitive(self, value: str) -> str:
         return value.lower() if not self.case_sensitive else value
@@ -279,8 +286,9 @@ def __init__(
         secrets_dir: str | Path | None = None,
         case_sensitive: bool | None = None,
         env_prefix: str | None = None,
+        env_ignore_empty: bool | None = None,
     ) -> None:
-        super().__init__(settings_cls, case_sensitive, env_prefix)
+        super().__init__(settings_cls, case_sensitive, env_prefix, env_ignore_empty)
         self.secrets_dir = secrets_dir if secrets_dir is not None else self.config.get('secrets_dir')
 
     def __call__(self) -> dict[str, Any]:
@@ -367,8 +375,9 @@ def __init__(
         case_sensitive: bool | None = None,
         env_prefix: str | None = None,
         env_nested_delimiter: str | None = None,
+        env_ignore_empty: bool | None = None,
     ) -> None:
-        super().__init__(settings_cls, case_sensitive, env_prefix)
+        super().__init__(settings_cls, case_sensitive, env_prefix, env_ignore_empty)
         self.env_nested_delimiter = (
             env_nested_delimiter if env_nested_delimiter is not None else self.config.get('env_nested_delimiter')
         )
@@ -377,9 +386,7 @@ def __init__(
         self.env_vars = self._load_env_vars()
 
     def _load_env_vars(self) -> Mapping[str, str | None]:
-        if self.case_sensitive:
-            return os.environ
-        return {k.lower(): v for k, v in os.environ.items()}
+        return parse_env_vars(os.environ, self.case_sensitive, self.env_ignore_empty)
 
     def get_field_value(self, field: FieldInfo, field_name: str) -> tuple[Any, str, bool]:
         """
@@ -562,17 +569,18 @@ def __init__(
         case_sensitive: bool | None = None,
         env_prefix: str | None = None,
         env_nested_delimiter: str | None = None,
+        env_ignore_empty: bool | None = None,
     ) -> None:
         self.env_file = env_file if env_file != ENV_FILE_SENTINEL else settings_cls.model_config.get('env_file')
         self.env_file_encoding = (
             env_file_encoding if env_file_encoding is not None else settings_cls.model_config.get('env_file_encoding')
         )
-        super().__init__(settings_cls, case_sensitive, env_prefix, env_nested_delimiter)
+        super().__init__(settings_cls, case_sensitive, env_prefix, env_nested_delimiter, env_ignore_empty)
 
     def _load_env_vars(self) -> Mapping[str, str | None]:
-        return self._read_env_files(self.case_sensitive)
+        return self._read_env_files()
 
-    def _read_env_files(self, case_sensitive: bool) -> Mapping[str, str | None]:
+    def _read_env_files(self) -> Mapping[str, str | None]:
         env_files = self.env_file
         if env_files is None:
             return {}
@@ -585,7 +593,12 @@ def _read_env_files(self, case_sensitive: bool) -> Mapping[str, str | None]:
             env_path = Path(env_file).expanduser()
             if env_path.is_file():
                 dotenv_vars.update(
-                    read_env_file(env_path, encoding=self.env_file_encoding, case_sensitive=case_sensitive)
+                    read_env_file(
+                        env_path,
+                        encoding=self.env_file_encoding,
+                        case_sensitive=self.case_sensitive,
+                        ignore_empty=self.env_ignore_empty,
+                    )
                 )
 
         return dotenv_vars
@@ -618,14 +631,25 @@ def __repr__(self) -> str:
         )
 
 
+def _get_env_var_key(key: str, case_sensitive: bool = False) -> str:
+    return key if case_sensitive else key.lower()
+
+
+def parse_env_vars(
+    env_vars: Mapping[str, str | None], case_sensitive: bool = False, ignore_empty: bool = False
+) -> Mapping[str, str | None]:
+    return {_get_env_var_key(k, case_sensitive): v for k, v in env_vars.items() if not (ignore_empty and v == '')}
+
+
 def read_env_file(
-    file_path: Path, *, encoding: str | None = None, case_sensitive: bool = False
+    file_path: Path,
+    *,
+    encoding: str | None = None,
+    case_sensitive: bool = False,
+    ignore_empty: bool = False,
 ) -> Mapping[str, str | None]:
     file_vars: dict[str, str | None] = dotenv_values(file_path, encoding=encoding or 'utf8')
-    if not case_sensitive:
-        return {k.lower(): v for k, v in file_vars.items()}
-    else:
-        return file_vars
+    return parse_env_vars(file_vars, case_sensitive, ignore_empty)
 
 
 def _annotation_is_complex(annotation: type[Any] | None, metadata: list[Any]) -> bool:

tests/test_settings.py

@@ -46,6 +46,12 @@ class SimpleSettings(BaseSettings):
     apple: str
 
 
+class SettingWithIgnoreEmpty(BaseSettings):
+    apple: str = 'default'
+
+    model_config = SettingsConfigDict(env_ignore_empty=True)
+
+
 def test_sub_env(env):
     env.set('apple', 'hello')
     s = SimpleSettings()
@@ -71,6 +77,44 @@ def test_other_setting():
         SimpleSettings(apple='a', foobar=42)
 
 
+def test_ignore_empty_when_empty_uses_default(env):
+    env.set('apple', '')
+    s = SettingWithIgnoreEmpty()
+    assert s.apple == 'default'
+
+
+def test_ignore_empty_when_not_empty_uses_value(env):
+    env.set('apple', 'a')
+    s = SettingWithIgnoreEmpty()
+    assert s.apple == 'a'
+
+
+def test_ignore_empty_with_dotenv_when_empty_uses_default(tmp_path):
+    p = tmp_path / '.env'
+    p.write_text('a=')
+
+    class Settings(BaseSettings):
+        a: str = 'default'
+
+        model_config = SettingsConfigDict(env_file=p, env_ignore_empty=True)
+
+    s = Settings()
+    assert s.a == 'default'
+
+
+def test_ignore_empty_with_dotenv_when_not_empty_uses_value(tmp_path):
+    p = tmp_path / '.env'
+    p.write_text('a=b')
+
+    class Settings(BaseSettings):
+        a: str = 'default'
+
+        model_config = SettingsConfigDict(env_file=p, env_ignore_empty=True)
+
+    s = Settings()
+    assert s.a == 'b'
+
+
 def test_with_prefix(env):
     class Settings(BaseSettings):
         apple: str
@@ -851,7 +895,7 @@ class Settings(BaseSettings):
     assert s.a == 'ignore non-file'
 
 
-def test_read_env_file_cast_sensitive(tmp_path):
+def test_read_env_file_case_sensitive(tmp_path):
     p = tmp_path / '.env'
     p.write_text('a="test"\nB=123')
 
@@ -976,14 +1020,19 @@ def test_read_dotenv_vars(tmp_path):
     prod_env = tmp_path / '.env.prod'
     prod_env.write_text(test_prod_env_file)
 
-    source = DotEnvSettingsSource(BaseSettings(), env_file=[base_env, prod_env], env_file_encoding='utf8')
-    assert source._read_env_files(case_sensitive=False) == {
+    source = DotEnvSettingsSource(
+        BaseSettings(), env_file=[base_env, prod_env], env_file_encoding='utf8', case_sensitive=False
+    )
+    assert source._read_env_files() == {
         'debug_mode': 'false',
         'host': 'https://example.com/services',
         'port': '8000',
     }
 
-    assert source._read_env_files(case_sensitive=True) == {
+    source = DotEnvSettingsSource(
+        BaseSettings(), env_file=[base_env, prod_env], env_file_encoding='utf8', case_sensitive=True
+    )
+    assert source._read_env_files() == {
         'debug_mode': 'false',
         'host': 'https://example.com/services',
         'Port': '8000',
@@ -992,9 +1041,9 @@ def test_read_dotenv_vars(tmp_path):
 
 def test_read_dotenv_vars_when_env_file_is_none():
     assert (
-        DotEnvSettingsSource(BaseSettings(), env_file=None, env_file_encoding=None)._read_env_files(
-            case_sensitive=False
-        )
+        DotEnvSettingsSource(
+            BaseSettings(), env_file=None, env_file_encoding=None, case_sensitive=False
+        )._read_env_files()
         == {}
     )