cli: Move the main code of export_graph to its own function

So it can be reused by a Luigi task

swh/dataset/cli.py

@@ -8,6 +8,7 @@
 import os
 import pathlib
 import sys
+from typing import Any, Dict, List, Optional, Set
 
 import click
 
@@ -93,23 +94,10 @@ AVAILABLE_EXPORTERS = {
     ),
 )
 @click.pass_context
-def export_graph(
-    ctx, export_path, export_id, formats, exclude, object_types, processes, margin
-):
+def export_graph(ctx, export_path, formats, exclude, object_types, **kwargs):
     """Export the Software Heritage graph as an edge dataset."""
-    from importlib import import_module
-    import logging
-    import resource
-    import uuid
-
-    from swh.dataset.journalprocessor import ParallelJournalProcessor
-
-    logger = logging.getLogger(__name__)
 
     config = ctx.obj["config"]
-    if not export_id:
-        export_id = str(uuid.uuid4())
-
     if object_types:
         object_types = {o.strip() for o in object_types.split(",")}
         invalid_object_types = object_types - set(MAIN_TABLES.keys())
@@ -128,6 +116,38 @@ def export_graph(
                 option_name="formats", message=f"{f} is not an available format."
             )
 
+    run_export_graph(
+        config,
+        pathlib.Path(export_path),
+        export_formats,
+        list(object_types),
+        exclude_obj_types=exclude_obj_types,
+        **kwargs,
+    )
+
+
+def run_export_graph(
+    config: Dict[str, Any],
+    export_path: pathlib.Path,
+    export_formats: List[str],
+    object_types: List[str],
+    exclude_obj_types: Set[str],
+    export_id: Optional[str],
+    processes: int,
+    margin: Optional[float],
+):
+    from importlib import import_module
+    import logging
+    import resource
+    import uuid
+
+    from swh.dataset.journalprocessor import ParallelJournalProcessor
+
+    logger = logging.getLogger(__name__)
+
+    if not export_id:
+        export_id = str(uuid.uuid4())
+
     # Enforce order (from origin to contents) to reduce number of holes in the graph.
     object_types = [
         obj_type for obj_type in MAIN_TABLES.keys() if obj_type in object_types
@@ -171,18 +191,14 @@ def export_graph(
         if obj_type in exclude_obj_types:
             continue
         exporters = [
-            (
-                exporter_cls[f],
-                {"export_path": os.path.join(export_path, f)},
-            )
-            for f in export_formats
+            (exporter_cls[f], {"export_path": export_path / f}) for f in export_formats
         ]
         parallel_exporter = ParallelJournalProcessor(
             config,
             exporters,
             export_id,
             obj_type,
-            node_sets_path=pathlib.Path(export_path) / ".node_sets" / obj_type,
+            node_sets_path=export_path / ".node_sets" / obj_type,
             processes=processes,
             offset_margin=margin,
         )