#48: Avoid module load order issue

CHANGELOG.md

@@ -1,3 +1,10 @@
+## Unreleased
+
+* Fixed:
+  * The plugin did not work on Fedora inside of Pip's isolated build
+    environment, because the plugin would be loaded before some of its
+    dependencies. Now, those imports are delayed until needed.
+
 ## v0.12.7 (2021-05-20)
 
 * Fixed:

poetry_dynamic_versioning/__init__.py

@@ -4,24 +4,13 @@
 import builtins
 import copy
 import functools
-import jinja2
 import os
 import re
 from importlib import import_module
 from pathlib import Path
-from typing import Mapping, MutableMapping, Optional, Sequence, Tuple
+from typing import Any, Mapping, MutableMapping, Optional, Sequence, Tuple
 
 import tomlkit
-from dunamai import (
-    bump_version,
-    check_version,
-    serialize_pep440,
-    serialize_pvp,
-    serialize_semver,
-    Style,
-    Vcs,
-    Version,
-)
 
 _VERSION_PATTERN = r"""
     (?x)                                                (?# ignore whitespace)
@@ -30,13 +19,17 @@
     (\+(?P<tagged_metadata>.+))?$                       (?# +linux)
 """.strip()
 
+# This is a placeholder for type hint docs since the actual type can't be
+# imported yet.
+_DUNAMAI_VERSION_ANY = Any
+
 
 class _ProjectState:
     def __init__(
         self,
         path: Path = None,
         original_version: str = None,
-        version: Tuple[Version, str] = None,
+        version: Tuple[_DUNAMAI_VERSION_ANY, str] = None,
         substitutions: MutableMapping[Path, str] = None,
     ) -> None:
         self.path = path
@@ -143,7 +136,9 @@ def get_config(start: Path = None) -> Mapping:
     return result
 
 
-def _bump_version_per_config(version: Version, bump: bool) -> Version:
+def _bump_version_per_config(version: _DUNAMAI_VERSION_ANY, bump: bool) -> _DUNAMAI_VERSION_ANY:
+    from dunamai import bump_version
+
     if not bump or version.distance == 0:
         return version
 
@@ -160,7 +155,19 @@ def _bump_version_per_config(version: Version, bump: bool) -> Version:
     return version
 
 
-def _get_version(config: Mapping) -> Tuple[Version, str]:
+def _get_version(config: Mapping) -> Tuple[_DUNAMAI_VERSION_ANY, str]:
+    import jinja2
+    from dunamai import (
+        bump_version,
+        check_version,
+        serialize_pep440,
+        serialize_pvp,
+        serialize_semver,
+        Style,
+        Vcs,
+        Version,
+    )
+
     vcs = Vcs(config["vcs"])
     style = config["style"]
     if style is not None: