add example, split get into new function

2 files changed, 30 insertions, 11 deletions

diff --git a/README.rst b/README.rst
index fd2f18c..8914fc8 100644
--- a/README.rst
+++ b/README.rst
@@ -628,6 +628,25 @@ The callable must return the configuration.
     )
 
 
+Customizing Version Scheme with pyproject.toml
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To support custom version schemes in pyproject.toml, you may specify your own function as an entrypoint for getting the version.
+
+.. code:: toml
+
+    # pyproject.toml
+    [tool.setuptools_scm]
+    version_scheme = "myproject.my_file:myversion_func"
+
+.. code:: python
+
+    # myproject/my_file
+    def myversion_func(version: ScmVersion):
+        from setuptools_scm.version import guess_next_version
+        return version.format_next_version(guess_next_version, '{guessed}b{distance}')
+
+
 Note on testing non-installed versions
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
diff --git a/src/setuptools_scm/version.py b/src/setuptools_scm/version.py
index 45647de..2377aed 100644
--- a/src/setuptools_scm/version.py
+++ b/src/setuptools_scm/version.py
@@ -494,6 +494,16 @@ def _get_ep(group: str, name: str) -> Any | None:
     else:
         return None
 
+def _get_from_object_reference_str(path: str) -> Any | None:
+    try:
+        from importlib.metadata import EntryPoint
+    except ImportError:
+        from importlib_metadata import EntryPoint
+    try:
+        return EntryPoint(path, path, None).load()
+    except (AttributeError, ModuleNotFoundError):
+        return None
+
 
 def _iter_version_schemes(
     entrypoint: str,
@@ -507,19 +517,9 @@ def _iter_version_schemes(
     if _memo is None:
         _memo = set()
     if isinstance(scheme_value, str):
-        tscheme_val = _get_ep(entrypoint, scheme_value)
-        if tscheme_val is None:
-            try:
-                from importlib.metadata import EntryPoint
-            except ImportError:
-                from importlib_metadata import EntryPoint
-            try:
-                tscheme_val = EntryPoint(scheme_value, scheme_value, entrypoint).load()
-            except (AttributeError, ModuleNotFoundError):
-                pass
         scheme_value = cast(
             'str|List[str]|Tuple[str, ...]|Callable[["ScmVersion"], str]|None',
-            tscheme_val
+            _get_ep(entrypoint, scheme_value) or _get_from_object_reference_str(scheme_value),
         )
 
     if isinstance(scheme_value, (list, tuple)):