Subprocess management: use a decorator

Use a decorator instead of a mixin to handle subprocess spawning and
monitoring

blender_common.py

@@ -1,13 +1,17 @@
 # -*- coding: utf-8 -*-
 # This file is for code dealing specifically with blender
 
+import logging
 import bpy
 from bpy.props import CollectionProperty
 from bpy.types import PropertyGroup, Panel, UIList, AddonPreferences, Operator
-from .subprocess_adapter import SubprocessOperatorMixin
+from .subprocess_adapter import subprocess_operator
+from . import bpackage as bpkg
 
 class RepositoryProperty(PropertyGroup):
     url = bpy.props.StringProperty(name="URL")
+    # status = bpy.props.EnumProperty(name="Status")
+
 
 class PACKAGE_UL_repositories(UIList):
     def draw_item(self, context, layout, data, item, icon, active_data, active_propname):
@@ -32,23 +36,37 @@ class PackagePreferences(AddonPreferences):
         col.operator("package.add_repository", icon="ZOOMIN", text="")
         col.operator("package.remove_repository", icon="ZOOMOUT", text="")
 
-class PACKAGE_OT_fetch(SubprocessOperatorMixin, bpy.types.Operator):
-    bl_idname = "package.fetch"
+        row = layout.row()
+        row.operator("package.refresh")
+
+
+@subprocess_operator
+class PACKAGE_OT_refresh(Operator):
+    bl_idname = "package.refresh"
     bl_label = "Update package list(s)"
 
-    last_response = None
+    log = logging.getLogger(__name__)
 
-    def __init__(self):
-        super().__init__()
-        settings = bpy.context.window_manager.package_manager_settings
-        self.subprocess = Process(target=blenderpack.fetch, args=(settings.url, self.pipe))
+    def invoke(self, context, event):
+        prefs = context.user_preferences.addons[__package__].preferences
+        if 'repositories' not in prefs:
+            return {'FINISHED'}
+        # HACK: just do the active repo for now
+        repo = bpkg.Repository(prefs['repositories'][prefs.active_repository].to_dict())
+        self.proc_args = []
+        self.proc_kwargs = {'target': repo.refresh}
+        
+    def execute(self, context, event):
+        pass
+
+    def modal(self, context, event):
+        # try:
+        self.poll_subprocess()
+        # except:
 
     def handle_response(self, resp):
-        self.__class__.last_response = resp
-        self.report({'INFO'}, "Request returned %s" % self.__class__.last_response)
+        self.report({'INFO'}, "Request returned %s" % resp)
 
-    def execute(self, context):
-        return {'FINISHED'}
 
 class PACKAGE_OT_add_repository(bpy.types.Operator):
     bl_idname = "package.add_repository"
@@ -73,7 +91,7 @@ def register():
     bpy.utils.register_class(RepositoryProperty)
     bpy.utils.register_class(PackagePreferences)
 
-    bpy.utils.register_class(PACKAGE_OT_fetch)
+    bpy.utils.register_class(PACKAGE_OT_refresh)
 
     bpy.utils.register_class(PACKAGE_OT_add_repository)
     bpy.utils.register_class(PACKAGE_OT_remove_repository)
@@ -83,7 +101,7 @@ def unregister():
     bpy.utils.unregister_class(RepositoryProperty)
     bpy.utils.unregister_class(PackagePreferences)
 
-    bpy.utils.unregister_class(PACKAGE_OT_fetch)
+    bpy.utils.unregister_class(PACKAGE_OT_refresh)
 
     bpy.utils.unregister_class(PACKAGE_OT_add_repository)
     bpy.utils.unregister_class(PACKAGE_OT_remove_repository)

bpackage/__init__.py

@@ -1,3 +1,3 @@
-import bpackage.exceptions
+from . import exceptions
 from .package import Package
 from .repository import Repository

bpackage/package.py

@@ -1,8 +1,8 @@
 #!/usr/bin/env python3
 
 # HACK: seems 'requests' module bundled with blender isn't bundled with 'idna' module. So force system python for now
-# import sys
-# sys.path.insert(0, '/usr/lib/python3.6/site-packages')
+import sys
+sys.path.insert(0, '/usr/lib/python3.6/site-packages')
 
 import logging
 

bpackage/repository.py

@@ -1,8 +1,8 @@
 #!/usr/bin/env python3
 
 # HACK: seems 'requests' module bundled with blender isn't bundled with 'idna' module. So force system python for now
-# import sys
-# sys.path.insert(0, '/usr/lib/python3.6/site-packages')
+import sys
+sys.path.insert(0, '/usr/lib/python3.6/site-packages')
 
 from pathlib import Path
 import requests
@@ -56,10 +56,15 @@ class Repository:
         req_headers = {}
 
         # Do things this way to avoid adding empty objects/None to the req_headers dict
-        if 'etag' in self._headers:
-            req_headers['If-None-Match'] = self._headers['etag']
-        if 'last-modified' in self._headers:
-            req_headers['If-Modified-Since'] = self._headers['last-modified']
+        if self._headers:
+            try:
+                req_headers['If-None-Match'] = self._headers['etag']
+            except KeyError:
+                pass
+            try:
+                req_headers['If-Modified-Since'] = self._headers['last-modified']
+            except KeyError:
+                pass
 
         #try
         resp = requests.get(self.url, headers=req_headers)

subprocess_adapter.py

@@ -1,39 +1,59 @@
 import logging
 from multiprocessing import Process, Pipe
+from bpy.types import Operator
 
-class SubprocessOperatorMixin:
-    timer = None
-    log = logging.getLogger("%s.SubprocessOperatorMixin" % __name__)
+def subprocess_operator(cls: Operator, polling_interval=.01) -> Operator:
+    """
+    Class decorator which wraps Operator methods with setup code for running a subprocess.
 
-    # run once in invoke
-    def setup(self):
-        pass
-    # run on receipt of data from subprocess
-    def handle_response(self, resp):
-        pass
+    Expects args for Process() to defined in cls.proc_args and cls.proc_kwargs. For example,
+    setting cls.proc_kwargs = {'target:' some_func} can be used to run 'some_func' in
+    a subprocess.
+    """
 
-    def __init__(self):
-        self.pipe = Pipe()
-        self.subprocess = None
+    def decoratify(cls, methodname, decorator):
+        """
+        Decorate `cls.methodname` with `decorator` if method `methodname` exists in cls
+        else just call the decorator with an empty function
+        """
+        orig_method = getattr(cls, methodname, None)
+        if orig_method:
+            setattr(cls, methodname, decorator(orig_method))
+        else:
+            # HACK: need a no-op which accepts any arguments
+            setattr(cls, methodname, decorator(lambda *args, **kwargs: None))
 
-    def execute(self, context):
-        return self.invoke(context, None)
 
-    def invoke(self, context, event):
-        self.subprocess.start()
-        # we have to explicitly close the end of the pipe we are NOT using,
-        # otherwise no exception will be generated when the other process closes its end.
-        self.pipe[1].close()
+    def decorate_execute(orig_execute):
+        def execute(self, context):
+            orig_execute(self, context)
+            call_copy_of_method_if_exist(cls, 'execute', self, context)
+            return self.invoke(context, None)
+        return execute
     
-        wm = context.window_manager
-        wm.modal_handler_add(self)
-        self.timer = wm.event_timer_add(.01, context.window)
 
-        self.setup()
+    def decorate_invoke(orig_invoke):
+        def invoke(self, context, event):
+            orig_invoke(self, context, event)
 
-        return {'RUNNING_MODAL'}
+            self.pipe = Pipe()
+            self.proc = Process(
+                    *getattr(self, 'proc_args', []),
+                    **getattr(self, 'proc_kwargs', [])
+                    )
+            self.proc.start()
+            # we have to explicitly close the end of the pipe we are NOT using,
+            # otherwise no exception will be generated when the other process closes its end.
+            self.pipe[1].close()
 
-    def modal(self, context, event):
+            wm = context.window_manager
+            wm.modal_handler_add(self)
+            self.timer = wm.event_timer_add(polling_interval, context.window)
+
+            return {'RUNNING_MODAL'}
+        return invoke
+
+    def poll_subprocess(self):
         self.log.debug("polling")
         try:
             if self.pipe[0].poll():
@@ -45,6 +65,13 @@ class SubprocessOperatorMixin:
             return {'FINISHED'}
 
         if newdata is not None:
-            self.handle_response(newdata)
+            self.handle_response(newdata) #TODO: make this a customizable callback
+            # this should allow chaining of multiple subprocess in a single operator
+
         return {'PASS_THROUGH'}
 
+    decoratify(cls, 'execute', decorate_execute)
+    decoratify(cls, 'invoke', decorate_invoke)
+    setattr(cls, 'poll_subprocess', poll_subprocess)
+
+    return cls