Define Configuration as a dataclass

We need to hack a bit in __setattr__() to preserve the current behaviour
but make dataclass fields initialization working.

We also add a unit test to check the behaviour when trying to change dataclass
fields, making sure they do not end up in 'entries'.

Author: dlax

pgtoolkit/conf.py

@@ -52,7 +52,7 @@
 from collections.abc import Iterable, Iterator
 from dataclasses import dataclass, field
 from datetime import timedelta
-from typing import IO, Any, NoReturn, Union
+from typing import IO, Any, ClassVar, NoReturn, Union
 from warnings import warn
 
 from ._helpers import JSONDateEncoder, open_or_return
@@ -401,6 +401,7 @@ def add(
         super().__setitem__(name, entry)
 
 
+@dataclass
 class Configuration:
     r"""Holds a parsed configuration.
 
@@ -457,29 +458,20 @@ class Configuration:
 
     """  # noqa
 
-    lines: list[str]
-    entries: dict[str, Entry]
-    path: str | None
-
-    _parameter_re = re.compile(
-        r"^(?P<name>[a-z_.]+)(?: +(?!=)| *= *)(?P<value>.*?)"
-        "[\\s\t]*"
-        r"(?P<comment>#.*)?$"
-    )
-
     # Internally, lines property contains an updated list of all comments and
     # entries serialized. When adding a setting or updating an existing one,
     # the serialized line is updated accordingly. This allows to keep comments
     # and serialize only what's needed. Other lines are just written as-is.
 
-    def __init__(self, path: str | None = None) -> None:
-        self.__dict__.update(
-            dict(
-                lines=[],
-                entries=OrderedDict(),
-                path=path,
-            )
-        )
+    path: str | None = None
+    lines: list[str] = field(default_factory=list, init=False)
+    entries: dict[str, Entry] = field(default_factory=OrderedDict, init=False)
+
+    _parameter_re: ClassVar = re.compile(
+        r"^(?P<name>[a-z_.]+)(?: +(?!=)| *= *)(?P<value>.*?)"
+        "[\\s\t]*"
+        r"(?P<comment>#.*)?$"
+    )
 
     def parse(self, fo: Iterable[str]) -> Iterator[tuple[pathlib.Path, IncludeType]]:
         for raw_line in fo:
@@ -552,13 +544,13 @@ def __iadd__(self, other: Any) -> Configuration:
 
     def __getattr__(self, name: str) -> Value:
         try:
-            return self[name]
+            return self.entries[name].value
         except KeyError:
             raise AttributeError(name)
 
     def __setattr__(self, name: str, value: Value) -> None:
-        if name in self.__dict__:
-            self.__dict__[name] = value
+        if name in self.__dataclass_fields__:
+            super().__setattr__(name, value)
         else:
             self[name] = value
 

tests/test_conf.py

@@ -159,6 +159,17 @@ def test_parser():
         parse(["bad_line"])
 
 
+def test_configuration_fields():
+    """Configuration fields (the ones from dataclass definition) can be changed."""
+    from pgtoolkit.conf import Configuration
+
+    cfg = Configuration(path="my/postgresql.conf")
+    assert cfg.path == "my/postgresql.conf"
+    cfg.path = "changed/to/postgres.conf"
+    assert cfg.path == "changed/to/postgres.conf"
+    assert "path" not in cfg and "path" not in cfg.entries
+
+
 def test_configuration_multiple_entries():
     from pgtoolkit.conf import Configuration