add dynamic Task (#106)

* add callable for Task arg. commands #101

* code review suggestions

* make is_dynamic_commands a getter-property

mara_pipelines/pipelines.py

@@ -1,7 +1,7 @@
 import copy
 import pathlib
 import re
-from typing import Optional, Dict, Set, List, Tuple, Union
+from typing import Optional, Dict, Set, List, Tuple, Union, Callable
 
 from . import config
 
@@ -81,24 +81,53 @@ def html_doc_items(self) -> List[Tuple[str, str]]:
 
 
 class Task(Node):
-    def __init__(self, id: str, description: str, commands: Optional[List[Command]] = None, max_retries: Optional[int] = None) -> None:
+    def __init__(self, id: str, description: str, commands: Optional[Union[Callable, List[Command]]] = None, max_retries: Optional[int] = None) -> None:
         super().__init__(id, description)
-        self.commands = []
         self.max_retries = max_retries
 
-        for command in commands or []:
-            self.add_command(command)
-
-    def add_command(self, command: Command, prepend=False):
+        if callable(commands):
+            self._commands = None
+            self.__dynamic_commands_generator_func = commands
+        else:
+            self._commands = []
+            self._add_commands(commands or [])
+
+    @property
+    def is_dynamic_commands(self) -> bool:
+        """if the command list is generated dynamically via a function"""
+        return self.__dynamic_commands_generator_func is not None
+
+    def _assert_is_not_dynamic(self):
+        if self.is_dynamic_commands:
+            raise Exception('You cannot use add_command when the task is constructed with a callable commands function.')
+
+    @property
+    def commands(self) -> List:
+        if self._commands is None:
+            self._commands = []
+            # execute the callable command function and cache the result
+            for command in self.__dynamic_commands_generator_func() or []:
+                self._add_command(command)
+        return self._commands
+
+    def _add_command(self, command: Command, prepend=False):
         if prepend:
-            self.commands.insert(0, command)
+            self._commands.insert(0, command)
         else:
-            self.commands.append(command)
+            self._commands.append(command)
         command.parent = self
 
-    def add_commands(self, commands: List[Command]):
+    def _add_commands(self, commands: List[Command]):
         for command in commands:
-            self.add_command(command)
+            self._add_command(command)
+
+    def add_command(self, command: Command, prepend=False):
+        self._assert_is_not_dynamic()
+        self._add_command(command, prepend=prepend)
+
+    def add_commands(self, commands: List[Command]):
+        self._assert_is_not_dynamic()
+        self._add_commands(commands)
 
     def run(self):
         for command in self.commands:

mara_pipelines/ui/node_page.py

@@ -80,6 +80,10 @@ def __(pipeline: pipelines.Pipeline):
 def __(task: pipelines.Task):
     if not acl.current_user_has_permission(views.acl_resource):
         return bootstrap.card(header_left='Commands', body=acl.inline_permission_denied_message())
+    elif task.is_dynamic_commands:
+        return bootstrap.card(
+            header_left='Commands',
+            body=f"""<span style="font-style:italic;color:#aaa"><span class="fa fa-lightbulb"> </span> {"... are defined dynamically during execution"}</span>""")
     else:
         commands_card = bootstrap.card(
             header_left='Commands',

tests/test_pipeline_tasks.py

@@ -0,0 +1,64 @@
+import pytest
+from typing import List
+
+from mara_pipelines.pipelines import Task
+from mara_pipelines.commands.python import RunFunction
+
+class _PythonFuncTestResult:
+    has_run = False
+
+
+def test_run_task():
+    """
+    A simple test executing a task.
+    """
+    test_result = _PythonFuncTestResult()
+
+    def python_test_function(result: _PythonFuncTestResult):
+        result.has_run = True  # noqa: F841
+
+    assert not test_result.has_run
+
+    task = Task(
+        id='run_task',
+        description="Unit test test_run_task",
+        commands=[RunFunction(function=python_test_function, args=[test_result])])
+
+    assert not test_result.has_run
+
+    task.run()
+
+    assert test_result.has_run
+
+
+def test_run_task_dynamic_commands():
+    """
+    A simple test executing a task with callable commands
+    """
+    import mara_pipelines.ui.node_page
+
+    test_result = _PythonFuncTestResult()
+
+    def python_test_function(result: _PythonFuncTestResult):
+        result.has_run = True  # noqa: F841
+
+    def generate_command_list() -> List:
+        yield RunFunction(function=lambda t: python_test_function(t), args=[test_result])
+
+    assert not test_result.has_run
+
+    task = Task(
+        id='run_task_dynamic_commands',
+        description="Unit test test_run_task_dynamic_commands",
+        commands=generate_command_list)
+
+    assert not test_result.has_run
+
+    content = mara_pipelines.ui.node_page.node_content(task)
+    assert content
+
+    assert not test_result.has_run
+
+    task.run()
+
+    assert test_result.has_run