mzworkflows: allow Python workflows to run Steps

Register each Step as a method of the Workflow class, which would
allow Steps to be called from within mzworkflows.py

misc/python/materialize/cli/mzcompose.py

@@ -18,9 +18,8 @@
 from pathlib import Path
 from typing import IO, List, Optional, Sequence, Text, Tuple
 
-from typing_extensions import NoReturn
-
 from materialize import errors, mzbuild, mzcompose, spawn, ui
+from typing_extensions import NoReturn
 
 announce = ui.speaker("==> ")
 say = ui.speaker("")

misc/python/materialize/mzcompose.py

@@ -51,9 +51,8 @@
 import pg8000  # type: ignore
 import pymysql
 import yaml
-from typing_extensions import Literal, TypedDict
-
 from materialize import errors, mzbuild, spawn, ui
+from typing_extensions import Literal, TypedDict
 
 T = TypeVar("T")
 say = ui.speaker("C> ")
@@ -197,7 +196,7 @@ def __init__(self, repo: mzbuild.Repository, name: str):
             compose = yaml.safe_load(f)
 
         # Stash away sub workflows so that we can load them with the correct environment variables
-        self.yaml_workflows = compose.pop("mzworkflows", None)
+        self.yaml_workflows = compose.pop("mzworkflows", {})
 
         # Load the mzworkflows.py file, if any.
         mzworkflows_py = self.path.parent / "mzworkflows.py"
@@ -600,7 +599,7 @@ def run(self) -> None:
         os.environ.update(self.env)
 
         try:
-            self.func(self.composition)
+            self.func(self)
         finally:
             os.environ.clear()
             os.environ.update(old_env)
@@ -619,18 +618,34 @@ def named(cls, name: str) -> Type["WorkflowStep"]:
             raise errors.UnknownItem("step", name, list(cls._steps))
 
     @classmethod
-    def register(cls, name: str) -> Callable[[Type[T]], Type[T]]:
+    def register(
+        cls, name: str
+    ) -> Callable[[Type["WorkflowStep"]], Type["WorkflowStep"]]:
         if name in cls._steps:
             raise ValueError(f"Double registration of step name: {name}")
 
-        def reg(to_register: Type[T]) -> Type[T]:
-            if not issubclass(to_register, WorkflowStep):
-                raise ValueError(
-                    f"Registered step must be a WorkflowStep: {to_register}"
-                )
+        def reg(to_register: Type["WorkflowStep"]) -> Type["WorkflowStep"]:
             cls._steps[name] = to_register
             to_register.name = name
-            return to_register  # type: ignore
+
+            # Allow the step to also be called as a Workflow.step_name() classmethod
+            def run_step(workflow: Workflow, **kwargs: Any) -> None:
+                step: WorkflowStep = to_register(**kwargs)
+                step.run(workflow)
+
+            func_name = name.replace("-", "_")
+            if func_name == "run":
+                # Temporary workaround for the fact that `Workflow.run` already
+                # exists.
+                func_name = "run_service"
+            if not hasattr(Workflow, func_name):
+                setattr(Workflow, func_name, run_step)
+            else:
+                raise errors.Failed(
+                    f"Unable to register method Workflow.{func_name} as one already exists."
+                )
+
+            return to_register
 
         return reg
 

test/mzworkflows_py/README.md

@@ -3,3 +3,6 @@ An example of python-based workflows that does not actually test anything.
 If the directory contains a file named mzworkflows.py, all functions
 from it that start with 'workflow_' will be made available for execution
 as if they are regular mzcompose.yml workflows.
+
+A Python workflow can call other Steps as methods to the Workflow,
+as shown in the mzworkflows.py example in this directory.

test/mzworkflows_py/mzcompose.yml

@@ -9,18 +9,6 @@
 
 version: '3.7'
 
-mzworkflows:
-  mzworkflows_py:
-    steps:
-      - step: start-services
-        services: [materialized]
-
-      - step: wait-for-mz
-        service: materialized
-
-      - step: workflow
-        workflow: workflow_in_python
-
 services:
   materialized:
     mzbuild: materialized

test/mzworkflows_py/mzworkflows.py

@@ -7,8 +7,10 @@
 # the Business Source License, use of this software will be governed
 # by the Apache License, Version 2.0.
 
-import materialize.mzcompose
+from materialize.mzcompose import Workflow
 
 
-def workflow_in_python(composition: materialize.mzcompose.Composition):
-    pass
+def workflow_in_python(w: Workflow):
+    w.start_services(services=["materialized"])
+    w.wait_for_mz(service="materialized")
+    w.kill_services(services=["materialized"])