1 files changed, 87 insertions, 0 deletions
diff --git a/taskcluster/taskgraph/transforms/cached_tasks.py b/taskcluster/taskgraph/transforms/cached_tasks.py
new file mode 100644
index 0000000000..283ee823cf
--- /dev/null
+++ b/taskcluster/taskgraph/transforms/cached_tasks.py
@@ -0,0 +1,87 @@
+# 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/.
+
+from __future__ import absolute_import, print_function, unicode_literals
+
+from collections import deque
+import taskgraph
+from taskgraph.transforms.base import TransformSequence
+from taskgraph.util.cached_tasks import add_optimization
+
+transforms = TransformSequence()
+
+
+def order_tasks(config, tasks):
+    """Iterate image tasks in an order where parent tasks come first."""
+    kind_prefix = config.kind + "-"
+
+    pending = deque(tasks)
+    task_labels = {task["label"] for task in pending}
+    emitted = set()
+    while True:
+        try:
+            task = pending.popleft()
+        except IndexError:
+            break
+        parents = {
+            task
+            for task in task.get("dependencies", {}).values()
+            if task.startswith(kind_prefix)
+        }
+        if parents and not emitted.issuperset(parents & task_labels):
+            pending.append(task)
+            continue
+        emitted.add(task["label"])
+        yield task
+
+
+def format_task_digest(cached_task):
+    return "/".join(
+        [
+            cached_task["type"],
+            cached_task["name"],
+            cached_task["digest"],
+        ]
+    )
+
+
+@transforms.add
+def cache_task(config, tasks):
+    if taskgraph.fast:
+        for task in tasks:
+            yield task
+        return
+
+    digests = {}
+    for task in config.kind_dependencies_tasks.values():
+        if "cached_task" in task.attributes:
+            digests[task.label] = format_task_digest(task.attributes["cached_task"])
+
+    for task in order_tasks(config, tasks):
+        cache = task.pop("cache", None)
+        if cache is None:
+            yield task
+            continue
+
+        dependency_digests = []
+        for p in task.get("dependencies", {}).values():
+            if p in digests:
+                dependency_digests.append(digests[p])
+            else:
+                raise Exception(
+                    "Cached task {} has uncached parent task: {}".format(
+                        task["label"], p
+                    )
+                )
+        digest_data = cache["digest-data"] + sorted(dependency_digests)
+        add_optimization(
+            config,
+            task,
+            cache_type=cache["type"],
+            cache_name=cache["name"],
+            digest_data=digest_data,
+        )
+        digests[task["label"]] = format_task_digest(task["attributes"]["cached_task"])
+
+        yield task