Prevents TOMLFile from changing line endings

.github/workflows/tests.yml

@@ -52,7 +52,7 @@ jobs:
         shell: bash
         run: |
           curl -fsS -o get-poetry.py https://raw.githubusercontent.com/sdispater/poetry/master/get-poetry.py
-          python get-poetry.py --preview -y
+          python get-poetry.py -y
           echo "$HOME/.poetry/bin" >> $GITHUB_PATH
           echo "%USERPROFILE%/.poetry/bin" >> $GITHUB_PATH
       - name: Setup Poetry

tests/test_toml_file.py

@@ -21,5 +21,45 @@ def test_toml_file(example):
         with io.open(toml_file, encoding="utf-8") as f:
             assert original_content == f.read()
     finally:
-        with io.open(toml_file, "w", encoding="utf-8") as f:
+        with io.open(toml_file, "w", encoding="utf-8", newline="") as f:
             assert f.write(original_content)
+
+
+def test_keep_old_eol(tmpdir):
+    toml_path = str(tmpdir / "pyproject.toml")
+    with io.open(toml_path, "wb+") as f:
+        f.write(b"a = 1\r\nb = 2\r\n")
+
+    f = TOMLFile(toml_path)
+    content = f.read()
+    content["b"] = 3
+    f.write(content)
+
+    with io.open(toml_path, "rb") as f:
+        assert f.read() == b"a = 1\r\nb = 3\r\n"
+
+
+def test_keep_old_eol_2(tmpdir):
+    toml_path = str(tmpdir / "pyproject.toml")
+    with io.open(toml_path, "wb+") as f:
+        f.write(b"a = 1\nb = 2\n")
+
+    f = TOMLFile(toml_path)
+    content = f.read()
+    content["b"] = 3
+    f.write(content)
+
+    with io.open(toml_path, "rb") as f:
+        assert f.read() == b"a = 1\nb = 3\n"
+
+
+def test_mixed_eol(tmpdir):
+    toml_path = str(tmpdir / "pyproject.toml")
+    with io.open(toml_path, "wb+") as f:
+        f.write(b"a = 1\r\nrb = 2\n")
+
+    f = TOMLFile(toml_path)
+    f.write(f.read())
+
+    with io.open(toml_path, "rb") as f:
+        assert f.read() == b"a = 1\r\nrb = 2\n"

tomlkit/toml_file.py

@@ -16,9 +16,9 @@ def __init__(self, path):  # type: (str) -> None
         self._path = path
 
     def read(self):  # type: () -> TOMLDocument
-        with io.open(self._path, encoding="utf-8") as f:
+        with io.open(self._path, encoding="utf-8", newline="") as f:
             return loads(f.read())
 
     def write(self, data):  # type: (TOMLDocument) -> None
-        with io.open(self._path, "w", encoding="utf-8") as f:
+        with io.open(self._path, "w", encoding="utf-8", newline="") as f:
             f.write(data.as_string())