Can't read Pydantic Settings from stdin

Fixes pydantic#296
Adds a method _read_env_file to DotEnvSettingsSource that can be easily overridden.
This fix keeps a global function so it can continue to be tested, but adds an underscore to the name.
The plain read_env_file is marked as deprecated.

Author: WarpedPixel

Diff for: pydantic_settings/sources.py

@@ -753,6 +753,18 @@ def __init__(
     def _load_env_vars(self) -> Mapping[str, str | None]:
         return self._read_env_files()
 
+    def _read_env_file(
+        self,
+        file_path: Path,
+    ) -> Mapping[str, str | None]:
+        return _read_env_file(
+            file_path,
+            encoding=self.env_file_encoding,
+            case_sensitive=self.case_sensitive,
+            ignore_empty=self.env_ignore_empty,
+            parse_none_str=self.env_parse_none_str,
+        )
+
     def _read_env_files(self) -> Mapping[str, str | None]:
         env_files = self.env_file
         if env_files is None:
@@ -765,15 +777,7 @@ def _read_env_files(self) -> Mapping[str, str | None]:
         for env_file in env_files:
             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=self.case_sensitive,
-                        ignore_empty=self.env_ignore_empty,
-                        parse_none_str=self.env_parse_none_str,
-                    )
-                )
+                dotenv_vars.update(self._read_env_file(env_path))
 
         return dotenv_vars
 
@@ -1708,6 +1712,27 @@ def read_env_file(
     case_sensitive: bool = False,
     ignore_empty: bool = False,
     parse_none_str: str | None = None,
+) -> Mapping[str, str | None]:
+    warnings.warn(
+        'read_env_file will be removed in the next version, use DotEnvSettingsSource._read_env_file instead',
+        DeprecationWarning,
+    )
+    return _read_env_file(
+        file_path,
+        encoding=encoding,
+        case_sensitive=case_sensitive,
+        ignore_empty=ignore_empty,
+        parse_none_str=parse_none_str,
+    )
+
+
+def _read_env_file(
+    file_path: Path,
+    *,
+    encoding: str | None = None,
+    case_sensitive: bool = False,
+    ignore_empty: bool = False,
+    parse_none_str: str | None = None,
 ) -> Mapping[str, str | None]:
     file_vars: dict[str, str | None] = dotenv_values(file_path, encoding=encoding or 'utf8')
     return parse_env_vars(file_vars, case_sensitive, ignore_empty, parse_none_str)

Diff for: tests/test_settings.py

@@ -49,7 +49,7 @@
     TomlConfigSettingsSource,
     YamlConfigSettingsSource,
 )
-from pydantic_settings.sources import CliPositionalArg, CliSettingsSource, CliSubCommand, SettingsError, read_env_file
+from pydantic_settings.sources import CliPositionalArg, CliSettingsSource, CliSubCommand, SettingsError, _read_env_file
 
 try:
     import dotenv
@@ -1039,15 +1039,15 @@ def test_read_env_file_case_sensitive(tmp_path):
     p = tmp_path / '.env'
     p.write_text('a="test"\nB=123')
 
-    assert read_env_file(p) == {'a': 'test', 'b': '123'}
-    assert read_env_file(p, case_sensitive=True) == {'a': 'test', 'B': '123'}
+    assert _read_env_file(p) == {'a': 'test', 'b': '123'}
+    assert _read_env_file(p, case_sensitive=True) == {'a': 'test', 'B': '123'}
 
 
 def test_read_env_file_syntax_wrong(tmp_path):
     p = tmp_path / '.env'
     p.write_text('NOT_AN_ASSIGNMENT')
 
-    assert read_env_file(p, case_sensitive=True) == {'NOT_AN_ASSIGNMENT': None}
+    assert _read_env_file(p, case_sensitive=True) == {'NOT_AN_ASSIGNMENT': None}
 
 
 def test_env_file_example(tmp_path):