Draft: Add test of execution of workflow with self-triggering task

For #16

Needs ewokscore!236 (merged)

src/ewoksppf/tests/test_self_triggering_task.py

+import pytest
+import os.path
+from ewokscore import Task
+from ewoksppf import execute_graph
+
+
+qualname = __name__
+
+
+def test_explicit_start_node_on_self_triggering_node(tmpdir):
+    """
+    Workflow:
+     - LOOP depends on itself (self-triggering task).
+     - SAVE depends on LOOP and CONFIG
+     - CONFIG does not depend on anything
+
+     /|
+    / |
+    LOOP -- SAVE
+            /
+           /
+          /
+    CONFIG
+
+    This test tests that, while graph analysis considers that the only
+    start node is CONFIG, it is possible to set `start_node` for LOOP
+    and make it a start node so that SAVE can get inputs from LOOP and
+    CONFIG.
+    """
+
+    class ConfigTask(Task, input_names=["filename"], output_names=["config"]):
+        def run(self):
+            self.outputs.config = {"filename": self.inputs.filename}
+
+    class LoopTask(
+        Task,
+        input_names=["i", "n"],
+        output_names=["i", "keep_looping"],
+    ):
+        def run(self):
+            self.outputs.i = self.inputs.i + 1
+            self.outputs.keep_looping = self.outputs.i < self.inputs.n
+
+    class SaveTask(
+        Task,
+        input_names=["config"],
+        optional_input_names=["i"],
+        output_names=["result"],
+    ):
+        def run(self):
+            if self.missing_inputs.i:
+                raise RuntimeError("LOOP not executed!")
+            config = self.inputs.config
+            with open(config["filename"], "a") as out_file:
+                out_file.write(f"LOOP executed: {self.inputs.i}")
+
+    workflow = {
+        "graph": {"id": "testworkflow"},
+        "nodes": [
+            {
+                "id": "CONFIG",
+                "task_type": "class",
+                "task_identifier": f"{qualname}.ConfigTask",
+            },
+            {
+                "id": "LOOP",
+                "task_type": "class",
+                "task_identifier": f"{qualname}.LoopTask",
+            },
+            {
+                "id": "SAVE",
+                "task_type": "class",
+                "task_identifier": f"{qualname}.SaveTask",
+            },
+        ],
+        "links": [
+            {
+                "source": "LOOP",
+                "target": "LOOP",
+                "data_mapping": [{"source_output": "i", "target_input": "i"}],
+                "conditions": [{"source_output": "keep_looping", "value": True}],
+            },
+            {
+                "source": "LOOP",
+                "target": "SAVE",
+                "data_mapping": [{"source_output": "i", "target_input": "i"}],
+            },
+            {
+                "source": "CONFIG",
+                "target": "SAVE",
+                "data_mapping": [{"source_output": "config", "target_input": "config"}],
+            },
+        ],
+    }
+
+    filename = str(tmpdir / "test.txt")
+    max_iterations = 10
+    inputs = [
+        {
+            "task_identifier": f"{qualname}.ConfigTask",
+            "name": "filename",
+            "value": filename,
+        },
+        {
+            "task_identifier": f"{qualname}.LoopTask",
+            "name": "i",
+            "value": 0,
+        },
+        {
+            "task_identifier": f"{qualname}.LoopTask",
+            "name": "n",
+            "value": max_iterations,
+        },
+    ]
+
+    # Execute without setting `force_start_node` in the LOOP node: the SAVE task fails.
+    with pytest.raises(RuntimeError) as e:
+        execute_graph(
+            workflow,
+            scaling_workers=False,
+            pool_type="thread",
+            inputs=inputs,
+        )
+        assert str(e) == "RuntimeError: Task 'SAVE' failed"
+    assert not os.path.exists(filename)
+
+    # Execute with `force_start_node` in the LOOP node; the SAVE task runs and the file exists.
+    loop_node = workflow["nodes"][1]
+    assert loop_node["id"] == "LOOP"
+    loop_node["force_start_node"] = True
+
+    execute_graph(
+        workflow,
+        scaling_workers=False,
+        pool_type="thread",
+        inputs=inputs,
+    )
+
+    with open(filename) as _file:
+        txt = _file.read()
+    for i in range(max_iterations):
+        assert str(i) in txt