Fix for tomlkit regression resulting in inconsistent line endings

src/poetry/core/toml/file.py

@@ -1,17 +1,64 @@
 from __future__ import annotations
 
+import os
+import re
+
 from pathlib import Path
 from typing import TYPE_CHECKING
 from typing import Any
 
+from tomlkit import loads
 from tomlkit.toml_file import TOMLFile as BaseTOMLFile
 
 
 if TYPE_CHECKING:
     from tomlkit.toml_document import TOMLDocument
 
 
-class TOMLFile(BaseTOMLFile):  # type: ignore[misc]
+class PatchedBaseTOMLFile(BaseTOMLFile):  # type: ignore[misc]
+    """
+    This class can be removed when https://github.com/sdispater/tomlkit/issues/200 is
+    resolved and changes from https://github.com/sdispater/tomlkit/pull/201 are
+    available.
+    """
+
+    def __init__(self, path: str) -> None:
+        super().__init__(path)
+        self._linesep = os.linesep
+
+    def read(self) -> TOMLDocument:
+        """Read the file content as a :class:`tomlkit.toml_document.TOMLDocument`."""
+        with open(self._path, encoding="utf-8", newline="") as f:
+            content = f.read()
+
+            # check if consistent line endings
+            num_newline = content.count("\n")
+            if num_newline > 0:
+                num_win_eol = content.count("\r\n")
+                if num_win_eol == num_newline:
+                    self._linesep = "\r\n"
+                elif num_win_eol == 0:
+                    self._linesep = "\n"
+                else:
+                    self._linesep = "mixed"
+
+            return loads(content)
+
+    def write(self, data: TOMLDocument) -> None:
+        """Write the TOMLDocument to the file."""
+        content = data.as_string()
+
+        # apply linesep
+        if self._linesep == "\n":
+            content = content.replace("\r\n", "\n")
+        elif self._linesep == "\r\n":
+            content = re.sub(r"(?<!\r)\n", "\r\n", content)
+
+        with open(self._path, "w", encoding="utf-8", newline="") as f:
+            f.write(content)
+
+
+class TOMLFile(PatchedBaseTOMLFile):
     def __init__(self, path: str | Path) -> None:
         if isinstance(path, str):
             path = Path(path)