fix: decode external data file content explicitly as UTF-8

copier/user_data.py

@@ -507,7 +507,7 @@ def load_answersfile_data(
 ) -> AnyByStrDict:
     """Load answers data from a `$dst_path/$answers_file` file if it exists."""
     try:
-        with open(Path(dst_path) / answers_file) as fd:
+        with Path(dst_path, answers_file).open(encoding="utf-8") as fd:
             return yaml.safe_load(fd)
     except (FileNotFoundError, IsADirectoryError):
         warnings.warn(

tests/test_answersfile.py

@@ -222,3 +222,31 @@ def test_external_data(tmp_path_factory: pytest.TempPathFactory) -> None:
         "parent2": "P2",
         "child": "C1",
     }
+
+
+def test_external_data_with_umlaut(
+    tmp_path_factory: pytest.TempPathFactory,
+) -> None:
+    src, dst = map(tmp_path_factory.mktemp, ("src", "dst"))
+
+    build_file_tree(
+        {
+            (src / "copier.yml"): (
+                """\
+                _external_data:
+                    data: data.yml
+                ext_umlaut: "{{ _external_data.data.umlaut }}"
+                """
+            ),
+            (src / "{{ _copier_conf.answers_file }}.jinja"): (
+                "{{ _copier_answers|to_nice_yaml }}"
+            ),
+        }
+    )
+    git_save(src, tag="v1")
+
+    (dst / "data.yml").write_text("umlaut: äöü", encoding="utf-8")
+
+    copier.run_copy(str(src), dst, defaults=True, overwrite=True)
+    answers = load_answersfile_data(dst, ".copier-answers.yml")
+    assert answers["ext_umlaut"] == "äöü"