1 files changed, 54 insertions, 0 deletions
diff --git a/third_party/python/taskcluster_taskgraph/taskgraph/util/taskgraph.py b/third_party/python/taskcluster_taskgraph/taskgraph/util/taskgraph.py
new file mode 100644
index 0000000000..7b545595ef
--- /dev/null
+++ b/third_party/python/taskcluster_taskgraph/taskgraph/util/taskgraph.py
@@ -0,0 +1,54 @@
+# 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/.
+
+"""
+Tools for interacting with existing taskgraphs.
+"""
+
+
+from taskgraph.util.taskcluster import find_task_id, get_artifact
+
+
+def find_decision_task(parameters, graph_config):
+    """Given the parameters for this action, find the taskId of the decision
+    task"""
+    if parameters.get("repository_type", "hg") == "hg":
+        return find_task_id(
+            "{}.v2.{}.pushlog-id.{}.decision".format(
+                graph_config["trust-domain"],
+                parameters["project"],
+                parameters["pushlog_id"],
+            )
+        )
+    elif parameters["repository_type"] == "git":
+        return find_task_id(
+            "{}.v2.{}.revision.{}.taskgraph.decision".format(
+                graph_config["trust-domain"],
+                parameters["project"],
+                parameters["head_rev"],
+            )
+        )
+    else:
+        raise Exception(
+            "Unknown repository_type {}!".format(parameters["repository_type"])
+        )
+
+
+def find_existing_tasks_from_previous_kinds(
+    full_task_graph, previous_graph_ids, rebuild_kinds
+):
+    """Given a list of previous decision/action taskIds and kinds to ignore
+    from the previous graphs, return a dictionary of labels-to-taskids to use
+    as ``existing_tasks`` in the optimization step."""
+    existing_tasks = {}
+    for previous_graph_id in previous_graph_ids:
+        label_to_taskid = get_artifact(previous_graph_id, "public/label-to-taskid.json")
+        kind_labels = {
+            t.label
+            for t in full_task_graph.tasks.values()
+            if t.attributes["kind"] not in rebuild_kinds
+        }
+        for label in set(label_to_taskid.keys()).intersection(kind_labels):
+            existing_tasks[label] = label_to_taskid[label]
+    return existing_tasks