Handle yaml vs yml ordering

Author: timkpaine

copier/_main.py

@@ -65,7 +65,7 @@
     StrOrPath,
     VcsRef,
 )
-from ._user_data import AnswersMap, Question, load_answersfile_data
+from ._user_data import AnswersMap, Question, load_answersfile_data, resolve_answersfile_path
 from ._vcs import get_git
 from .errors import (
     CopierAnswersInterrupt,
@@ -1027,10 +1027,11 @@ def resolved_vcs_ref(self) -> str | None:
     @cached_property
     def subproject(self) -> Subproject:
         """Get related subproject."""
-        default_answers_file = Path(".copier-answers.yaml") if Path(".copier-answers.yaml").exists() else Path(".copier-answers.yml")
+        # answers_file=None means auto-detect based on existing files
+        # The Subproject will use resolve_answersfile_path to determine which file to use
         result = Subproject(
             local_abspath=self.dst_path.absolute(),
-            answers_relpath=self.answers_file or default_answers_file,
+            answers_relpath=self.answers_file,
         )
         self._cleanup_hooks.append(result._cleanup)
         return result

copier/_subproject.py

@@ -15,7 +15,7 @@
 
 from ._template import Template
 from ._types import AbsolutePath, AnyByStrDict, VCSTypes
-from ._user_data import load_answersfile_data
+from ._user_data import load_answersfile_data, resolve_answersfile_path
 from ._vcs import get_git, is_in_git_repo
 
 
@@ -29,10 +29,11 @@ class Subproject:
 
         answers_relpath:
             Relative path to [the answers file][the-copier-answersyml-file].
+            If None, auto-detects between .copier-answers.yml and .copier-answers.yaml.
     """
 
     local_abspath: AbsolutePath
-    answers_relpath: Path = Path(".copier-answers.yml")
+    answers_relpath: Path | None = None
 
     _cleanup_hooks: list[Callable[[], None]] = field(default_factory=list, init=False)
 
@@ -53,6 +54,17 @@ def _cleanup(self) -> None:
         for method in self._cleanup_hooks:
             method()
 
+    @cached_property
+    def resolved_answers_relpath(self) -> Path:
+        """Get the resolved answers file path.
+
+        If answers_relpath was explicitly set, return it.
+        Otherwise, auto-detect based on existing files (.yml takes precedence).
+        """
+        if self.answers_relpath is not None:
+            return self.answers_relpath
+        return resolve_answersfile_path(self.local_abspath)
+
     @property
     def _raw_answers(self) -> AnyByStrDict:
         """Get last answers, loaded raw as yaml."""

copier/_template.py

@@ -24,6 +24,7 @@
 
 from ._tools import copier_version, handle_remove_readonly
 from ._types import AnyByStrDict, VCSTypes
+from ._user_data import DEFAULT_ANSWERS_FILE_YML
 from ._vcs import checkout_latest_tag, clone, get_git, get_repo
 from .errors import (
     InvalidConfigFileError,
@@ -272,10 +273,12 @@ def answers_relpath(self) -> Path:
         """Get the answers file relative path, as specified in the template.
 
         If not specified, returns the default `.copier-answers.yml`.
+        Note: The actual file used may be `.copier-answers.yaml` if that exists
+        and `.copier-answers.yml` does not. This is handled by the subproject.
 
         See [answers_file][].
         """
-        result = Path(self.config_data.get("answers_file", ".copier-answers.yml"))
+        result = Path(self.config_data.get("answers_file", DEFAULT_ANSWERS_FILE_YML))
         assert not result.is_absolute()
         return result
 

copier/_user_data.py

@@ -39,6 +39,10 @@
 )
 from .errors import InvalidTypeError, MissingFileWarning, UserMessageError
 
+# Default answers file names, in order of precedence
+DEFAULT_ANSWERS_FILE_YML = ".copier-answers.yml"
+DEFAULT_ANSWERS_FILE_YAML = ".copier-answers.yaml"
+
 
 # TODO Remove these two functions as well as DEFAULT_DATA in a future release
 def _now() -> datetime:
@@ -585,11 +589,50 @@ def parse_yaml_list(string: str) -> list[str]:
 
 def load_answersfile_data(
     dst_path: StrOrPath,
-    answers_file: StrOrPath = ".copier-answers.yml",
+    answers_file: StrOrPath | None = None,
     *,
     warn_on_missing: bool = False,
 ) -> AnyByStrDict:
-    """Load answers data from a `$dst_path/$answers_file` file if it exists."""
+    """Load answers data from a `$dst_path/$answers_file` file if it exists.
+
+    Args:
+        dst_path: Path to the destination directory.
+        answers_file: Path to the answers file relative to dst_path.
+            If None, auto-detects by checking for .copier-answers.yml first,
+            then .copier-answers.yaml. The .yml extension takes precedence.
+        warn_on_missing: If True, warn when the answers file is not found.
+
+    Returns:
+        The loaded answers data, or an empty dict if not found.
+    """
+    dst = Path(dst_path)
+
+    # If answers_file is None, auto-detect
+    if answers_file is None:
+        yml_path = dst / DEFAULT_ANSWERS_FILE_YML
+        yaml_path = dst / DEFAULT_ANSWERS_FILE_YAML
+
+        yml_exists = yml_path.is_file()
+        yaml_exists = yaml_path.is_file()
+
+        # Warn if both files exist
+        if yml_exists and yaml_exists:
+            warnings.warn(
+                f"Both {DEFAULT_ANSWERS_FILE_YML} and {DEFAULT_ANSWERS_FILE_YAML} "
+                f"exist in {dst_path}. Using {DEFAULT_ANSWERS_FILE_YML}. "
+                "Please remove the duplicate file.",
+                stacklevel=2,
+            )
+
+        # .yml takes precedence, fall back to .yaml
+        if yml_exists:
+            answers_file = DEFAULT_ANSWERS_FILE_YML
+        elif yaml_exists:
+            answers_file = DEFAULT_ANSWERS_FILE_YAML
+        else:
+            # Default to .yml when neither exists
+            answers_file = DEFAULT_ANSWERS_FILE_YML
+
     try:
         with Path(dst_path, answers_file).open("rb") as fd:
             return yaml.safe_load(fd)
@@ -602,6 +645,46 @@ def load_answersfile_data(
         return {}
 
 
+def resolve_answersfile_path(dst_path: StrOrPath) -> Path:
+    """Resolve which answers file to use for a given destination path.
+
+    For reading: Returns the existing answers file (.yml takes precedence over .yaml).
+    For writing: Returns the existing file to update, or .yml as default for new files.
+
+    Warns if both .yml and .yaml files exist.
+
+    Args:
+        dst_path: Path to the destination directory.
+
+    Returns:
+        Relative path to the answers file to use.
+    """
+    dst = Path(dst_path)
+    yml_path = dst / DEFAULT_ANSWERS_FILE_YML
+    yaml_path = dst / DEFAULT_ANSWERS_FILE_YAML
+
+    yml_exists = yml_path.is_file()
+    yaml_exists = yaml_path.is_file()
+
+    # Warn if both files exist
+    if yml_exists and yaml_exists:
+        warnings.warn(
+            f"Both {DEFAULT_ANSWERS_FILE_YML} and {DEFAULT_ANSWERS_FILE_YAML} "
+            f"exist in {dst_path}. Using {DEFAULT_ANSWERS_FILE_YML}. "
+            "Please remove the duplicate file.",
+            stacklevel=2,
+        )
+
+    # .yml takes precedence for reading/updating
+    if yml_exists:
+        return Path(DEFAULT_ANSWERS_FILE_YML)
+    # If only .yaml exists, use it (maintains backwards compatibility for .yaml projects)
+    elif yaml_exists:
+        return Path(DEFAULT_ANSWERS_FILE_YAML)
+    # Default to .yml for new files
+    return Path(DEFAULT_ANSWERS_FILE_YML)
+
+
 CAST_STR_TO_NATIVE: Mapping[str, Callable[[str], Any]] = {
     "bool": cast_to_bool,
     "float": float,