feat: add scaffolding and basic tests for taskgraph generation

This is prep work for mozilla#628, where I'd like to add some tests to avoid regressing that again in the future.

The fixtures here are based on similar tests from Gecko: https://searchfox.org/mozilla-central/source/taskcluster/test. There's a bit of a terrible hack to make optimized task graphs testable, described more in the comments.

Taskfile.yml

@@ -180,6 +180,13 @@ tasks:
         --output-file "{{.OUTPUT_FILE}}"
         --diff "{{.BASE_REV}}"
 
+  taskgraph-test:
+    desc: Run tests and validations against task generation
+    cmds:
+      - >-
+        poetry run --directory taskgraph --
+        pytest taskcluster/test
+
   docs:
     desc: Run the GitHub pages Jekyll theme locally.
     cmds:

pyproject.toml

@@ -53,6 +53,7 @@ sh = "^2.0.6"
 zstandard = "^0.22.0"
 translations_parser = {path="./tracking/", develop=true}
 taskcluster-taskgraph = "^10.0.1"
+translations_taskgraph = {path="./taskcluster/", develop=true}
 
 [tool.black]
 extend-exclude= "/3rd_party"

taskcluster/pyproject.toml

@@ -1,3 +1,19 @@
+[build-system]
+requires = [ "setuptools>=61.2",]
+build-backend = "setuptools.build_meta"
+
+[project]
+name = "translations_taskgraph"
+version = "0.1.0"
+description = "Translations specific code needed to generate Taskcluster tasks & graphs"
+requires-python = ">=3.10"
+
+[tool.setuptools]
+include-package-data = true
+
+[tool.setuptools.packages.find]
+namespaces = false
+
 [tool.ruff]
 line-length = 120
 target-version = "py37"

taskcluster/test/conftest.py

@@ -0,0 +1,74 @@
+from copy import deepcopy
+import pytest
+import requests_mock
+
+from taskgraph.generator import TaskGraphGenerator
+from taskgraph.parameters import parameters_loader
+from translations_taskgraph.util.substitution import substitute
+
+
+# These fixtures are largely cribbed from Gecko:
+# https://searchfox.org/mozilla-central/source/taskcluster/test
+@pytest.fixture(scope="session")
+def create_tgg():
+    def inner(parameters=None, overrides=None) -> TaskGraphGenerator:
+        params = parameters_loader(parameters, strict=False, overrides=overrides)
+        return TaskGraphGenerator(None, params)
+
+    return inner
+
+
+@pytest.fixture(scope="module")
+def mock_requests():
+    with requests_mock.Mocker() as m:
+        yield m
+
+
+# Scoping this at the module level means that each module will only generate
+# a taskgraph one time, no matter how many tests are within it. This is
+# beneficial for performance reasons, but forces any tests that need distinct
+# parameters to be moved to their own modules.
+@pytest.fixture(scope="module")
+def tgg(request, create_tgg) -> TaskGraphGenerator:
+    if not hasattr(request.module, "PARAMS"):
+        pytest.fail("'tgg' fixture requires a module-level 'PARAMS' variable")
+
+    return create_tgg(overrides=request.module.PARAMS)
+
+
+@pytest.fixture(scope="module")
+def full_task_graph(tgg):
+    return tgg.full_task_graph
+
+
+@pytest.fixture(scope="module")
+def target_task_graph(tgg: TaskGraphGenerator):
+    return tgg.target_task_graph
+
+
+@pytest.fixture(scope="module")
+def target_task_set(tgg: TaskGraphGenerator):
+    return tgg.target_task_set
+
+
+@pytest.fixture(scope="module")
+def optimized_task_graph(request, mock_requests, tgg: TaskGraphGenerator):
+    for resp in getattr(request.module, "MOCK_REQUESTS", {}):
+        responses = deepcopy(resp["responses"])
+        digests = {}
+        # This is a bit of a terribly hack, but it allows for cached task digests
+        # to be substituted into mocked API responses, which is needed to test
+        # the optimized and/or morphed task graph. Cached task digests are
+        # generated as part of earlier phases, so there's no sensible way for
+        # them to defined concretely at the same time as other parts of the
+        # MOCK_REQUESTS.
+        for label, key in resp.get("substitute_digest", {}).items():
+            digests[key] = tgg.full_task_set[label].attributes["cached_task"]["digest"]
+        responses = substitute(responses, **digests)
+        mock_requests.request(
+            resp["method"],
+            resp["url"],
+            responses,
+        )
+
+    return tgg.optimized_task_graph

taskcluster/test/test_default_params.py

@@ -0,0 +1,97 @@
+from copy import deepcopy
+
+from translations_taskgraph.parameters import get_defaults
+
+PARAMS = deepcopy(get_defaults(None))
+PARAMS["target_tasks_method"] = "train-target-tasks"
+
+MOCK_REQUESTS = [
+    {
+        "substitute_digest": {
+            "build-docker-image-base": "digest_base",
+            "build-docker-image-test": "digest_test",
+            "build-docker-image-toolchain-build": "digest_toolchain",
+            "build-docker-image-train": "digest_train",
+        },
+        "method": "POST",
+        "url": "https://firefox-ci-tc.services.mozilla.com/api/index/v1/tasks/indexes",
+        "responses": [
+            {
+                "json": {
+                    "tasks": [
+                        {
+                            "namespace": "translations.cache.level-3.docker-images.v2.base.hash.{digest_base}",
+                            "taskId": "build-docker-image-base",
+                        },
+                        {
+                            "namespace": "translations.cache.level-3.docker-images.v2.test.hash.{digest_test}",
+                            "taskId": "build-docker-image-test",
+                        },
+                        {
+                            "namespace": "translations.cache.level-3.docker-images.v2.toolchain-build.hash.{digest_toolchain}",
+                            "taskId": "build-docker-image-toolchain-build",
+                        },
+                        {
+                            "namespace": "translations.cache.level-3.docker-images.v2.train.hash.{digest_train}",
+                            "taskId": "build-docker-image-train",
+                        },
+                    ],
+                },
+                "status_code": 200,
+            },
+        ],
+    },
+    {
+        "method": "POST",
+        "url": "https://firefox-ci-tc.services.mozilla.com/api/queue/v1/tasks/status",
+        "responses": [
+            {
+                "json": {
+                    "statuses": [
+                        {
+                            "status": {
+                                "state": "completed",
+                                "expires": "3024-08-21T22:37:28.781Z",
+                            },
+                            "taskId": "build-docker-image-base",
+                        },
+                        {
+                            "status": {
+                                "state": "completed",
+                                "expires": "3024-08-21T22:37:28.781Z",
+                            },
+                            "taskId": "build-docker-image-test",
+                        },
+                        {
+                            "status": {
+                                "state": "completed",
+                                "expires": "3024-08-21T22:37:28.781Z",
+                            },
+                            "taskId": "build-docker-image-toolchain-build",
+                        },
+                        {
+                            "status": {
+                                "state": "completed",
+                                "expires": "3024-08-21T22:37:28.781Z",
+                            },
+                            "taskId": "build-docker-image-train",
+                        },
+                    ],
+                },
+                "status_code": 200,
+            },
+        ],
+    },
+]
+
+
+def test_last_task_is_targeted(target_task_set):
+    """Ensure that the last task in the pipeline is targeted by default"""
+    assert any([task == "all-ru-en-1" for task in target_task_set.tasks])
+
+
+def test_cached_tasks_optimized_away(optimized_task_graph):
+    """Ensure that any tasks found in a cache route are _not_ present
+    in the optimized graph (ie: they will not be scheduled)."""
+    for task in optimized_task_graph.tasks.values():
+        assert not task.label.startswith("build-docker-image")

taskcluster/test/test_target_stage.py

@@ -0,0 +1,17 @@
+from copy import deepcopy
+
+from translations_taskgraph.parameters import get_defaults
+
+PARAMS = deepcopy(get_defaults(None))
+PARAMS["target_tasks_method"] = "train-target-tasks"
+PARAMS["training_config"]["target-stage"] = "train-teacher"
+
+
+def test_nothing_downstream_of_target(target_task_graph):
+    # despite being called `reverse_links_dict`, this actually
+    # gives us a dict where we can find tasks _downstream_ of
+    # each task by label
+    links = target_task_graph.graph.reverse_links_dict()
+    for task in target_task_graph.graph.nodes:
+        if task.startswith("train-teacher"):
+            assert links[task] == set()

taskcluster/test/test_training_continuation_backwards.py

@@ -0,0 +1,26 @@
+from copy import deepcopy
+
+from translations_taskgraph.parameters import get_defaults
+
+PARAMS = deepcopy(get_defaults(None))
+PARAMS["target_tasks_method"] = "train-target-tasks"
+PARAMS["training_config"]["experiment"]["pretrained-models"] = {
+    "train-backwards": {
+        "mode": "use",
+        "type": "default",
+        "urls": [
+            "https://storage.googleapis.com/releng-translations-dev/models/ru-en/better-teacher/student"
+        ],
+    },
+}
+
+
+def test_artifact_mounts(full_task_graph):
+    task = [t for t in full_task_graph.tasks.values() if t.label == "train-backwards-ru-en"][0]
+    # No need to bother looking for _all_ files (we'd just duplicate
+    # the full list if we did that...), but we verify that one file
+    # is well formed.
+    mounted_files = {m["file"]: m for m in task.task["payload"]["mounts"] if "file" in m}
+    assert mounted_files["./artifacts/model.npz"]["content"] == {
+        "url": "https://storage.googleapis.com/releng-translations-dev/models/ru-en/better-teacher/student/model.npz",
+    }