Refactor preferred visualization logic

 to eliminate circular import between datatypes registry and managers.
 Move get_preferred_visualization from registry to datatypes manager
 module where the class hierarchy mapping logic already exists.

Author: dannon

lib/galaxy/datatypes/registry.py

@@ -516,56 +516,6 @@ def get_legacy_sites_by_build(self, site_type, build):
     def get_display_sites(self, site_type):
         return self.display_sites.get(site_type, [])
 
-    def get_preferred_visualization(self, datatype_extension):
-        """
-        Get the preferred visualization mapping for a specific datatype extension.
-        Returns a dictionary with 'visualization' and 'default_params' keys, or None if no mapping exists.
-
-        Preferred visualizations are defined inline within each datatype definition in the
-        datatypes_conf.xml configuration file. These mappings determine which visualization plugin
-        should be used by default when viewing datasets of a specific type.
-
-        If no direct mapping exists for the extension, this method will walk up the inheritance
-        chain to find a preferred visualization from a parent datatype class.
-
-        Example configuration:
-        <datatype extension="bam" type="galaxy.datatypes.binary:Bam" mimetype="application/octet-stream" display_in_upload="true">
-            <visualization plugin="igv" />
-        </datatype>
-        """
-        direct_mapping = self.visualization_mappings.get(datatype_extension)
-        if direct_mapping:
-            return direct_mapping
-
-        current_datatype = self.get_datatype_by_extension(datatype_extension)
-        if not current_datatype:
-            return None
-
-        # Use the same mapping approach as the datatypes API for consistency
-        from galaxy.managers.datatypes import view_mapping
-
-        mapping_data = view_mapping(self)
-
-        current_class_name = mapping_data.ext_to_class_name.get(datatype_extension)
-        if not current_class_name:
-            return None
-
-        current_class_mappings = mapping_data.class_to_classes.get(current_class_name, {})
-
-        # Find parent extensions that have preferred visualizations
-        for ext, visualization_mapping in self.visualization_mappings.items():
-            if ext == datatype_extension:
-                continue
-
-            parent_class_name = mapping_data.ext_to_class_name.get(ext)
-            if parent_class_name and parent_class_name in current_class_mappings:
-                self.log.debug(
-                    f"Found inherited preferred visualization '{visualization_mapping['visualization']}' for datatype '{datatype_extension}' from parent '{ext}'"
-                )
-                return visualization_mapping
-
-        return None
-
     def get_all_visualization_mappings(self):
         """
         Get all datatype to visualization mappings.

lib/galaxy/managers/datatypes.py

@@ -163,6 +163,51 @@ def view_visualization_mappings(
     return parse_obj_as(DatatypeVisualizationMappingsList, mappings)
 
 
+def get_preferred_visualization(datatypes_registry: Registry, datatype_extension: str) -> Optional[Dict[str, str]]:
+    """
+    Get the preferred visualization mapping for a specific datatype extension.
+    Returns a dictionary with 'visualization' and 'default_params' keys, or None if no mapping exists.
+
+    Preferred visualizations are defined inline within each datatype definition in the
+    datatypes_conf.xml configuration file. These mappings determine which visualization plugin
+    should be used by default when viewing datasets of a specific type.
+
+    If no direct mapping exists for the extension, this method will walk up the inheritance
+    chain to find a preferred visualization from a parent datatype class.
+
+    Example configuration:
+    <datatype extension="bam" type="galaxy.datatypes.binary:Bam" mimetype="application/octet-stream" display_in_upload="true">
+        <visualization plugin="igv" />
+    </datatype>
+    """
+    direct_mapping = datatypes_registry.visualization_mappings.get(datatype_extension)
+    if direct_mapping:
+        return direct_mapping
+
+    current_datatype = datatypes_registry.get_datatype_by_extension(datatype_extension)
+    if not current_datatype:
+        return None
+
+    # Use the same mapping approach as the datatypes API for consistency
+    mapping_data = view_mapping(datatypes_registry)
+
+    current_class_name = mapping_data.ext_to_class_name.get(datatype_extension)
+    if not current_class_name:
+        return None
+
+    current_class_mappings = mapping_data.class_to_classes.get(current_class_name, {})
+
+    for ext, visualization_mapping in datatypes_registry.visualization_mappings.items():
+        if ext == datatype_extension:
+            continue
+
+        parent_class_name = mapping_data.ext_to_class_name.get(ext)
+        if parent_class_name and parent_class_name in current_class_mappings:
+            return visualization_mapping
+
+    return None
+
+
 __all__ = (
     "DatatypeConverterList",
     "DatatypeDetails",
@@ -179,4 +224,5 @@ def view_visualization_mappings(
     "view_edam_formats",
     "view_edam_data",
     "view_visualization_mappings",
+    "get_preferred_visualization",
 )

lib/galaxy/webapps/galaxy/api/datatypes.py

@@ -26,6 +26,7 @@
     DatatypesEDAMDetailsDict,
     DatatypesMap,
     DatatypeVisualizationMappingsList,
+    get_preferred_visualization,
     view_converters,
     view_edam_data,
     view_edam_formats,
@@ -258,7 +259,7 @@ async def show(
             result["converters"] = list(converters.keys())
 
         # Add preferred visualization if any and if the plugin is available
-        preferred_viz = self.datatypes_registry.get_preferred_visualization(datatype)
+        preferred_viz = get_preferred_visualization(self.datatypes_registry, datatype)
         if preferred_viz:
             plugin_name = preferred_viz["visualization"]