allow None and str for project_dir in NominatimAPI init

src/nominatim_db/config.py

@@ -59,15 +59,17 @@ class Configuration:
         other than string.
     """
 
-    def __init__(self, project_dir: Optional[Path],
+    def __init__(self, project_dir: Optional[Union[Path, str]],
                  environ: Optional[Mapping[str, str]] = None) -> None:
         self.environ = environ or os.environ
-        self.project_dir = project_dir
         self.config_dir = paths.CONFIG_DIR
         self._config = dotenv_values(str(self.config_dir / 'env.defaults'))
-        if self.project_dir is not None and (self.project_dir / '.env').is_file():
-            self.project_dir = self.project_dir.resolve()
-            self._config.update(dotenv_values(str(self.project_dir / '.env')))
+        if project_dir is not None:
+            self.project_dir: Optional[Path] = Path(project_dir).resolve()
+            if (self.project_dir / '.env').is_file():
+                self._config.update(dotenv_values(str(self.project_dir / '.env')))
+        else:
+            self.project_dir = None
 
         class _LibDirs:
             module: Path

src/nominatim_db/tools/convert_sqlite.py

@@ -7,7 +7,7 @@
 """
 Exporting a Nominatim database to SQlite.
 """
-from typing import Set, Any
+from typing import Set, Any, Optional, Union
 import datetime as dt
 import logging
 from pathlib import Path
@@ -21,7 +21,8 @@ from nominatim_api.sql.sqlalchemy_types import Geometry, IntArray
 
 LOG = logging.getLogger()
 
-async def convert(project_dir: Path, outfile: Path, options: Set[str]) -> None:
+async def convert(project_dir: Optional[Union[str, Path]],
+                  outfile: Path, options: Set[str]) -> None:
     """ Export an existing database to sqlite. The resulting database
         will be usable against the Python frontend of Nominatim.
     """