SDK - Compiler - Fixed ParallelFor name clashes

The ParallelFor argument reference resolving was really broken.
The logic "worked" like this - of the name of the referenced output
contained the name of the loop collection source output, then it was
considered to be the reference to the loop item.
This broke lots of scenarios especially in cases where there were
multiple components with same output name (e.g. the default "Output"
output name). The logic also did not distinguish between references to
the loop collection item vs. references to the loop collection source
itself.

I've rewritten the argument resolving logic, to fix the issues.

sdk/python/kfp/compiler/compiler.py

@@ -473,7 +473,7 @@ def _group_to_dag_template(self, group, inputs, outputs, dependencies):
           # i.e., rather than a static list, they are either the output of another task or were input
           # as global pipeline parameters
 
-          pipeline_param = sub_group.loop_args
+          pipeline_param = sub_group.loop_args.items_or_pipeline_param
           if pipeline_param.op_name is None:
             withparam_value = '{{workflow.parameters.%s}}' % pipeline_param.name
           else:
@@ -528,19 +528,25 @@ def get_arguments_for_sub_group(
       else:
         argument_name = param_name
 
-      # default argument_value + special cases
-      argument_value = '{{inputs.parameters.%s}}' % param_name
+      # Preparing argument. It can be pipeline input reference, task output reference or loop item (or loop item attribute
+      sanitized_loop_arg_full_name = '---'
       if isinstance(sub_group, dsl.ParallelFor):
-        if sub_group.loop_args.name in param_name:
-          if _for_loop.LoopArgumentVariable.name_is_loop_arguments_variable(param_name):
-            subvar_name = _for_loop.LoopArgumentVariable.get_subvar_name(param_name)
-            argument_value = '{{item.%s}}' % subvar_name
-          elif _for_loop.LoopArguments.name_is_loop_arguments(param_name) or sub_group.items_is_pipeline_param:
-            argument_value = '{{item}}'
-          else:
-            raise ValueError("Failed to match loop args with parameter. param_name: {}, ".format(param_name))
-      elif dependent_name:
-        argument_value = '{{tasks.%s.outputs.parameters.%s}}' % (dependent_name, param_name)
+        sanitized_loop_arg_full_name = sanitize_k8s_name(self._pipelineparam_full_name(sub_group.loop_args))
+      arg_ref_full_name = sanitize_k8s_name(param_name)
+      # We only care about the reference to the current loop item, not the outer loops
+      if isinstance(sub_group, dsl.ParallelFor) and arg_ref_full_name.startswith(sanitized_loop_arg_full_name):
+        if arg_ref_full_name == sanitized_loop_arg_full_name:
+          argument_value = '{{item}}'
+        elif _for_loop.LoopArgumentVariable.name_is_loop_arguments_variable(param_name):
+          subvar_name = _for_loop.LoopArgumentVariable.get_subvar_name(param_name)
+          argument_value = '{{item.%s}}' % subvar_name
+        else:
+          raise ValueError("Argument seems to reference the loop item, but not the item itself and not some attribute of the item. param_name: {}, ".format(param_name))
+      else:
+        if dependent_name:
+          argument_value = '{{tasks.%s.outputs.parameters.%s}}' % (dependent_name, param_name)
+        else:
+          argument_value = '{{inputs.parameters.%s}}' % param_name
 
       arguments.append({
         'name': argument_name,

sdk/python/kfp/dsl/_for_loop.py

@@ -10,6 +10,7 @@ class LoopArguments(dsl.PipelineParam):
     """Class representing the arguments that are looped over in a ParallelFor loop in the KFP DSL.
     This doesn't need to be instantiated by the end user, rather it will be automatically created by a
     ParallelFor ops group."""
+    LOOP_ITEM_NAME_BASE = 'loop-item'
     LOOP_ITEM_PARAM_NAME_BASE = 'loop-item-param'
     # number of characters in the code which is passed to the constructor
     NUM_CODE_CHARS = 8
@@ -52,7 +53,7 @@ def __init__(self, items: Union[ItemList, dsl.PipelineParam], code: Text, name_o
                 if not self._subvar_name_is_legal(subvar_name):
                     raise ValueError("Tried to create subvariable named {} but that's not a legal Python variable "
                                      "name.".format(subvar_name))
-                setattr(self, subvar_name, LoopArgumentVariable(self.name, subvar_name))
+                setattr(self, subvar_name, LoopArgumentVariable(self.name, subvar_name, loop_args_op_name=self.op_name))
 
         self.items_or_pipeline_param = items
         self.referenced_subvar_names = []
@@ -62,7 +63,7 @@ def from_pipeline_param(cls, param: dsl.PipelineParam) -> 'LoopArguments':
         return LoopArguments(
             items=param,
             code=None,
-            name_override=param.name,
+            name_override=param.name + '-' + cls.LOOP_ITEM_NAME_BASE,
             op_name=param.op_name,
             value=param.value,
         )
@@ -71,7 +72,7 @@ def __getattr__(self, item):
         # this is being overridden so that we can access subvariables of the LoopArguments (i.e.: item.a) without
         # knowing the subvariable names ahead of time
         self.referenced_subvar_names.append(item)
-        return LoopArgumentVariable(self.name, item)
+        return LoopArgumentVariable(self.name, item, loop_args_op_name=self.op_name)
 
     def to_list_for_task_yaml(self):
         if isinstance(self.items_or_pipeline_param, (list, tuple)):
@@ -86,20 +87,29 @@ def _make_name(cls, code: Text):
         return '{}-{}'.format(cls.LOOP_ITEM_PARAM_NAME_BASE, code)
 
     @classmethod
-    def name_is_loop_arguments(cls, param_name: Text) -> bool:
+    def name_is_withitems_loop_argument(cls, param_name: Text) -> bool:
         """Return True if the given parameter name looks like it came from a loop arguments parameter."""
         return re.match(
             '%s-[0-9a-f]{%s}' % (cls.LOOP_ITEM_PARAM_NAME_BASE, cls.NUM_CODE_CHARS),
             param_name,
         ) is not None
 
+    @classmethod
+    def name_is_withparams_loop_argument(cls, param_name: Text) -> bool:
+        """Return True if the given parameter name looks like it came from a withParams loop item."""
+        return ('-' + cls.LOOP_ITEM_NAME_BASE) in param_name
 
 class LoopArgumentVariable(dsl.PipelineParam):
     """Represents a subvariable for loop arguments.  This is used for cases where we're looping over maps,
     each of which contains several variables."""
     SUBVAR_NAME_DELIMITER = '-subvar-'
 
-    def __init__(self, loop_args_name: Text, this_variable_name: Text):
+    def __init__(
+        self,
+        loop_args_name: Text,
+        this_variable_name: Text,
+        loop_args_op_name: Text,
+    ):
         """
         If the user ran:
             with dsl.ParallelFor([{'a': 1, 'b': 2}, {'a': 3, 'b': 4}]) as item:
@@ -111,7 +121,11 @@ def __init__(self, loop_args_name: Text, this_variable_name: Text):
             this_variable_name: the name of this subvariable, which is the name of the dict key that spawned
                 this subvariable.
         """
-        super().__init__(name=self.get_name(loop_args_name=loop_args_name, this_variable_name=this_variable_name))
+        super().__init__(
+            name=self.get_name(loop_args_name=loop_args_name,
+            this_variable_name=this_variable_name),
+            op_name=loop_args_op_name,
+        )
 
     @classmethod
     def get_name(cls, loop_args_name: Text, this_variable_name: Text) -> Text:

sdk/python/tests/compiler/compiler_tests.py

@@ -783,6 +783,9 @@ def test_withparam_output_dict(self):
   def test_withparam_lightweight_out(self):
     self._test_py_compile_yaml('loop_over_lightweight_output')
 
+  def test_parallelfor_name_clashes(self):
+    self._test_py_compile_yaml('parallelfor_name_clashes')
+
   def test_py_input_artifact_raw_value(self):
     """Test pipeline input_artifact_raw_value."""
     self._test_py_compile_yaml('input_artifact_raw_value')

sdk/python/tests/compiler/testdata/loop_over_lightweight_output.yaml

@@ -36,13 +36,13 @@
           - |-
             echo
           - |-
-            {{inputs.parameters.produce-list-data_list}}
+            {{inputs.parameters.produce-list-data_list-loop-item}}
         "image": |-
           busybox
       "inputs":
         "parameters":
           - "name": |-
-              produce-list-data_list
+              produce-list-data_list-loop-item
       "metadata":
         "annotations":
           "pipelines.kubeflow.org/component_spec": |-
@@ -54,25 +54,25 @@
           - "arguments":
               "parameters":
                 - "name": |-
-                    produce-list-data_list
+                    produce-list-data_list-loop-item
                   "value": |-
-                    {{inputs.parameters.produce-list-data_list}}
+                    {{inputs.parameters.produce-list-data_list-loop-item}}
             "name": |-
               consume-data
             "template": |-
               consume-data
       "inputs":
         "parameters":
           - "name": |-
-              produce-list-data_list
+              produce-list-data_list-loop-item
       "name": |-
         for-loop-for-loop-00000001-1
     - "dag":
         "tasks":
           - "arguments":
               "parameters":
                 - "name": |-
-                    produce-list-data_list
+                    produce-list-data_list-loop-item
                   "value": |-
                     {{item}}
             "dependencies":

sdk/python/tests/compiler/testdata/parallelfor_name_clashes.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python3
+# Copyright 2020 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from typing import NamedTuple
+
+import kfp
+from kfp.components import func_to_container_op
+
+@func_to_container_op
+def produce_str() -> str:
+    return "Hello"
+
+@func_to_container_op
+def produce_list() -> list:
+    return ["1", "2"]
+
+@func_to_container_op
+def consume(param1):
+    print(param1)
+
+@kfp.dsl.pipeline()
+def parallelfor_name_clashes_pipeline():
+    produce_str_task = produce_str()
+    produce_list_task = produce_list()
+    with kfp.dsl.ParallelFor(produce_list_task.output) as loop_item:
+        consume(produce_list_task.output)
+        consume(produce_str_task.output)
+        consume(loop_item)
+        consume(loop_item.aaa)
+
+
+if __name__ == '__main__':
+    import kfp.compiler as compiler
+    compiler.Compiler().compile(parallelfor_name_clashes_pipeline, __file__ + '.yaml')
+