Corrected PulpImport/Export handling of sub-content.

fixes #2192.
[nocoverage]

(cherry picked from commit 849d410)

CHANGES/2192.bugfix

@@ -0,0 +1,5 @@
+Fixed import/export of repositories with sub-content.
+
+An example would be the sub-repositories in pulp_rpm
+DistributionTrees.
+

pulpcore/app/importexport.py

@@ -118,10 +118,6 @@ def _combine_content_mappings(map1, map2):
         )
     )
 
-    # Export the connection between content and artifacts
-    resource = ContentArtifactResource(repository_version)
-    _write_export(export.tarfile, resource, dest_dir)
-
     # content mapping is used by repo versions with subrepos (eg distribution tree repos)
     content_mapping = {}
 
@@ -138,6 +134,10 @@ def _combine_content_mappings(map1, map2):
                     content_mapping, resource.content_mapping
                 )
 
+    # Export the connection between content and artifacts
+    resource = ContentArtifactResource(repository_version, content_mapping)
+    _write_export(export.tarfile, resource, dest_dir)
+
     msg = (
         f"Exporting content for {plugin_name} "
         f"repository-version {repository_version.repository.name}/{repository_version.number}"

pulpcore/app/modelresource.py

@@ -66,12 +66,19 @@ class ContentArtifactResource(QueryModelResource):
     ContentArtifact is different from other import-export entities because it has no 'natural key'
     other than a pulp_id, which aren't shared across instances. We do some magic to link up
     ContentArtifacts to their matching (already-imported) Content.
+
+    Some plugin-models have sub-repositories. We take advantage of the content-mapping
+    machinery to account for those contentartifacts as well.
     """
 
     artifact = fields.Field(
         column_name="artifact", attribute="artifact", widget=ForeignKeyWidget(Artifact, "sha256")
     )
 
+    def __init__(self, repo_version=None, content_mapping=None):
+        self.content_mapping = content_mapping
+        super().__init__(repo_version)
+
     def before_import_row(self, row, **kwargs):
         """
         Fixes the content-ptr of an incoming content-artifact row at import time.
@@ -92,9 +99,15 @@ def before_import_row(self, row, **kwargs):
         row["content"] = str(linked_content.pulp_id)
 
     def set_up_queryset(self):
-        return ContentArtifact.objects.filter(content__in=self.repo_version.content).order_by(
-            "content", "relative_path"
-        )
+        vers_content = ContentArtifact.objects.filter(content__in=self.repo_version.content)
+        if self.content_mapping:
+            all_content = []
+            for content_ids in self.content_mapping.values():
+                all_content.extend(content_ids)
+            vers_content = vers_content.union(
+                ContentArtifact.objects.filter(content__in=all_content)
+            )
+        return vers_content.order_by("content", "relative_path")
 
     class Meta:
         model = ContentArtifact