Allow plugins to define early import stage functions

beets/importer.py

@@ -313,6 +313,8 @@ class ImportSession(object):
                 stages += [import_asis(self)]
 
             # Plugin stages.
+            for stage_func in plugins.early_import_stages():
+                stages.append(plugin_stage(self, stage_func))
             for stage_func in plugins.import_stages():
                 stages.append(plugin_stage(self, stage_func))
 

beets/plugins.py

@@ -81,6 +81,7 @@ class BeetsPlugin(object):
             self.template_fields = {}
         if not self.album_template_fields:
             self.album_template_fields = {}
+        self.early_import_stages = []
         self.import_stages = []
 
         self._log = log.getChild(self.name)
@@ -94,6 +95,17 @@ class BeetsPlugin(object):
         """
         return ()
 
+    def get_early_import_stages(self):
+        """Return a list of functions that should be called as importer
+        pipelines stages early in the pipeline.
+
+        The callables are wrapped versions of the functions in
+        `self.early_import_stages`. Wrapping provides some bookkeeping for the
+        plugin: specifically, the logging level is adjusted to WARNING.
+        """
+        return [self._set_log_level_and_params(logging.WARNING, import_stage)
+                for import_stage in self.early_import_stages]
+
     def get_import_stages(self):
         """Return a list of functions that should be called as importer
         pipelines stages.
@@ -393,6 +405,14 @@ def template_funcs():
     return funcs
 
 
+def early_import_stages():
+    """Get a list of early import stage functions defined by plugins."""
+    stages = []
+    for plugin in find_plugins():
+        stages += plugin.get_early_import_stages()
+    return stages
+
+
 def import_stages():
     """Get a list of import stage functions defined by plugins."""
     stages = []