Bug 1795921 - [taskgraph] Use an 'enable_always_target' param to control when 'always_target' should apply, r=releng-reviewers,gbrown

This is a bit more general purpose and flexible than hardcoding `hg-push` here.
It is also something that can be upstreamed to standalone taskgraph.

Differential Revision: https://phabricator.services.mozilla.com/D160536

taskcluster/docs/parameters.rst

@@ -134,6 +134,13 @@ those in the target set, recursively.  In a decision task, this set can be
 specified programmatically using one of a variety of methods (e.g., parsing try
 syntax or reading a project-specific configuration file).
 
+``enable_always_target``
+    When ``True``, any task with the ``always_target`` attribute will be
+    included in the ``target_task_graph`` regardless of whether they were
+    filtered out by the ``target_tasks_method`` or not. Because they are not
+    part of the ``target_set``, they will still be eligible for optimization
+    when the ``optimize_target_tasks`` parameter is ``False``.
+
 ``filters``
     List of filter functions (from ``taskcluster/gecko_taskgraph/filter_tasks.py``) to
     apply. This is usually defined internally, as filters are typically

taskcluster/gecko_taskgraph/decision.py

@@ -52,6 +52,7 @@ ARTIFACTS_DIR = "artifacts"
 # See `taskcluster/docs/parameters.rst` for information on parameters.
 PER_PROJECT_PARAMETERS = {
     "try": {
+        "enable_always_target": True,
         "target_tasks_method": "try_tasks",
     },
     "kaios-try": {
@@ -336,6 +337,7 @@ def get_decision_parameters(graph_config, options):
     parameters["filters"] = [
         "target_tasks_method",
     ]
+    parameters["enable_always_target"] = False
     parameters["existing_tasks"] = {}
     parameters["do_not_optimize"] = []
     parameters["build_number"] = 1

taskcluster/gecko_taskgraph/generator.py

@@ -359,7 +359,7 @@ class TaskGraphGenerator:
             if t.attributes["kind"] == "docker-image"
         }
         # include all tasks with `always_target` set
-        if parameters["tasks_for"] == "hg-push":
+        if parameters["enable_always_target"]:
             always_target_tasks = {
                 t.label
                 for t in full_task_graph.tasks.values()

taskcluster/gecko_taskgraph/parameters.py

@@ -20,6 +20,7 @@ gecko_parameters_schema = {
     Required("app_version"): str,
     Required("backstop"): bool,
     Required("build_number"): int,
+    Required("enable_always_target"): bool,
     Required("hg_branch"): str,
     Required("message"): str,
     Required("next_version"): Any(None, str),
@@ -67,6 +68,7 @@ def get_defaults(repo_root=None):
         "backstop": False,
         "base_repository": "https://hg.mozilla.org/mozilla-unified",
         "build_number": 1,
+        "enable_always_target": False,
         "head_repository": "https://hg.mozilla.org/mozilla-central",
         "hg_branch": "default",
         "message": "",

taskcluster/gecko_taskgraph/test/conftest.py

@@ -158,6 +158,7 @@ def maketgg(monkeypatch):
             {
                 "_kinds": kinds,
                 "backstop": False,
+                "enable_always_target": False,
                 "target_tasks_method": "test_method",
                 "test_manifest_loader": "default",
                 "try_mode": None,

taskcluster/gecko_taskgraph/test/test_generator.py

@@ -90,7 +90,7 @@ def test_always_target_tasks(maketgg):
                 },
             ),
         ],
-        "params": {"optimize_target_tasks": False},
+        "params": {"optimize_target_tasks": False, "enable_always_target": True},
     }
     tgg = maketgg(**tgg_args)
     assert sorted(tgg.target_task_set.tasks.keys()) == sorted(

taskcluster/test/params/try.yml

@@ -6,6 +6,7 @@ app_version: 60.0a1
 version: 60.0a1
 next_version: null
 do_not_optimize: []
+enable_always_target: true
 existing_tasks: {}
 filters:
     - target_tasks_method