1 files changed, 77 insertions, 0 deletions
diff --git a/taskcluster/gecko_taskgraph/optimize/strategies.py b/taskcluster/gecko_taskgraph/optimize/strategies.py
new file mode 100644
index 0000000000..4d0d23a5ac
--- /dev/null
+++ b/taskcluster/gecko_taskgraph/optimize/strategies.py
@@ -0,0 +1,77 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+import logging
+
+import mozpack.path as mozpath
+from mozbuild.base import MozbuildObject
+from mozbuild.util import memoize
+from taskgraph.optimize.base import OptimizationStrategy, register_strategy
+
+from gecko_taskgraph import files_changed
+
+logger = logging.getLogger(__name__)
+
+
+@register_strategy("skip-unless-schedules")
+class SkipUnlessSchedules(OptimizationStrategy):
+    @memoize
+    def scheduled_by_push(self, repository, revision):
+        changed_files = files_changed.get_changed_files(repository, revision)
+
+        mbo = MozbuildObject.from_environment()
+        # the decision task has a sparse checkout, so, mozbuild_reader will use
+        # a MercurialRevisionFinder with revision '.', which should be the same
+        # as `revision`; in other circumstances, it will use a default reader
+        rdr = mbo.mozbuild_reader(config_mode="empty")
+
+        components = set()
+        for p, m in rdr.files_info(changed_files).items():
+            components |= set(m["SCHEDULES"].components)
+
+        return components
+
+    def should_remove_task(self, task, params, conditions):
+        if params.get("pushlog_id") == -1:
+            return False
+
+        scheduled = self.scheduled_by_push(
+            params["head_repository"], params["head_rev"]
+        )
+        conditions = set(conditions)
+        # if *any* of the condition components are scheduled, do not optimize
+        if conditions & scheduled:
+            return False
+
+        return True
+
+
+@register_strategy("skip-unless-has-relevant-tests")
+class SkipUnlessHasRelevantTests(OptimizationStrategy):
+    """Optimizes tasks that don't run any tests that were
+    in child directories of a modified file.
+    """
+
+    @memoize
+    def get_changed_dirs(self, repo, rev):
+        changed = map(mozpath.dirname, files_changed.get_changed_files(repo, rev))
+        # Filter out empty directories (from files modified in the root).
+        # Otherwise all tasks would be scheduled.
+        return {d for d in changed if d}
+
+    def should_remove_task(self, task, params, _):
+        if not task.attributes.get("test_manifests"):
+            return True
+
+        for d in self.get_changed_dirs(params["head_repository"], params["head_rev"]):
+            for t in task.attributes["test_manifests"]:
+                if t.startswith(d):
+                    logger.debug(
+                        "{} runs a test path ({}) contained by a modified file ({})".format(
+                            task.label, t, d
+                        )
+                    )
+                    return False
+        return True