Implement #250

pyblish/logic.py

@@ -348,6 +348,12 @@ def Iterator(plugins, context, state=None):
 
     """
 
+    # Run ContextPlugin only if instance of family is present when not "*"
+    # This is to preserve backwards compatility.
+    PYBLISH_CONTEXTPLUGIN_ON_FAMILY = bool(
+        os.getenv("PYBLISH_CONTEXTPLUGIN_ON_FAMILY")
+    )
+
     test = registered_test()
     state = state or {
         "nextOrder": None,
@@ -381,4 +387,13 @@ def Iterator(plugins, context, state=None):
                 yield plugin, instance
 
         else:
+
+            if PYBLISH_CONTEXTPLUGIN_ON_FAMILY:
+                # When filtering to families at least a single instance with
+                # that family must be active in the current publish
+                if "*" not in plugin.families:
+                    if not any(instance.data.get("publish") is not False
+                               for instance in instances):
+                        continue
+
             yield plugin, None

tests/lib.py

@@ -76,3 +76,18 @@ def tempdir():
         yield tempdir
     finally:
         shutil.rmtree(tempdir)
+
+
+@contextlib.contextmanager
+def env_override(overrides):
+    """Temporarily override environment variables"""
+    assert isinstance(overrides, dict)
+    original = os.environ.copy()
+    os.environ.update(overrides)
+
+    try:
+        yield
+    finally:
+        # Reset
+        os.environ.clear()
+        os.environ.update(original)

tests/test_logic.py

@@ -67,6 +67,66 @@ def process(self, instance):
     assert count["#"] == 101, count
 
 
+@with_setup(lib.setup, lib.teardown)
+def test_contextplugin_on_family_iterator():
+    """Iterator skips ContextPlugin filtered to family
+
+    This functionality is only enabled when PYBLISH_CONTEXTPLUGIN_ON_FAMILY
+    environment variable is set to a True value to preserve backwards
+    compatibility.
+
+    """
+
+    count = {"#": 0}
+
+    class MyCollector(api.ContextPlugin):
+        order = api.CollectorOrder
+
+        def process(self, context):
+            instance = context.create_instance("A1")
+            instance.data['families'] = ["A"]
+            instance = context.create_instance("A2")
+            instance.data['families'] = ["A"]
+            instance = context.create_instance("C1")
+            instance.data['families'] = ["C"]
+
+            count["#"] += 1
+
+    class ValidateA(api.ContextPlugin):
+        families = ["A"]
+        order = api.CollectorOrder
+
+        def process(self, context):
+            count["#"] += 10
+
+    class ValidateB(api.ContextPlugin):
+        families = ["B"]
+        order = api.CollectorOrder
+
+        def process(self, context):
+            count["#"] += 100
+
+    class ValidateAC(api.ContextPlugin):
+        families = ["A", "C"]
+        order = api.CollectorOrder
+
+        def process(self, context):
+            count["#"] += 1000
+
+    context = api.Context()
+    plugins = [MyCollector, ValidateA, ValidateB, ValidateAC]
+
+    assert count["#"] == 0, count
+
+    with lib.env_override({"PYBLISH_CONTEXTPLUGIN_ON_FAMILY": "True"}):
+        for Plugin, instance in logic.Iterator(plugins, context):
+            assert Plugin.__name__ != "ValidateB"
+            plugin.process(Plugin, context, instance)
+
+    # Collector runs once, one Validator runs once
+    assert count["#"] == 1011, count
+
+
 def test_register_gui():
     """Registering at run-time takes precedence over those from environment"""