fix: double-check importing correctly errors if render neither behave…

…s as a package nor isolated module

tests/_lib/unfrender.py

@@ -0,0 +1,29 @@
+"""Testing example renderer.
+
+Correctly fails to import to show a broken module being handled.
+"""
+
+from typing import Unpack, TypedDict
+from dewret.workflow import Workflow
+
+# This lacking a relative import, while extra itself
+# uses one is what breaks the module. It cannot be both
+# a package and not-a-package. This is importable by
+# adding a . before extra. If instead, you try to avoid
+# relative imports altogether, and change .other -> other
+# in extra, it will also break, as the directory of this
+# file is not in the PATH.
+from extra import JUMP # type: ignore
+
+class UnfrenderRendererConfiguration(TypedDict):
+    allow_complex_types: bool
+
+def default_config() -> UnfrenderRendererConfiguration:
+    return {
+        "allow_complex_types": True
+    }
+
+def render_raw(
+    workflow: Workflow, **kwargs: Unpack[UnfrenderRendererConfiguration]
+) -> dict[str, str]:
+    return {"JUMP": str(JUMP)}

tests/test_render_module.py

@@ -1,5 +1,6 @@
 """Check renderers can be imported live."""
 
+import pytest
 from pathlib import Path
 from dewret.tasks import construct
 from dewret.render import get_render_method
@@ -41,3 +42,16 @@ def test_can_load_render_module() -> None:
 It probably got made with JUMP=1.0
 """,
     }
+
+def test_get_correct_import_error_if_unable_to_load_render_module() -> None:
+    """TODO: Docstrings."""
+    unfrender_py = Path(__file__).parent / "_lib/unfrender.py"
+    with pytest.raises(ImportError) as exc:
+      get_render_method(unfrender_py)
+
+    entry = exc.traceback[-1]
+    assert Path(entry.path).resolve() == (
+        Path(__file__).parent / "_lib" / "extra.py"
+    ).resolve()
+    assert entry.relline == 2
+    assert "attempted relative import with no known parent package" in str(exc.value)