1 files changed, 61 insertions, 0 deletions
diff --git a/taskcluster/taskgraph/loader/transform.py b/taskcluster/taskgraph/loader/transform.py
new file mode 100644
index 0000000000..f611775766
--- /dev/null
+++ b/taskcluster/taskgraph/loader/transform.py
@@ -0,0 +1,61 @@
+# 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
+
+import logging
+
+import six
+
+from ..util.templates import merge
+from ..util.yaml import load_yaml
+
+logger = logging.getLogger(__name__)
+
+
+def loader(kind, path, config, params, loaded_tasks):
+    """
+    Get the input elements that will be transformed into tasks in a generic
+    way.  The elements themselves are free-form, and become the input to the
+    first transform.
+
+    By default, this reads jobs from the `jobs` key, or from yaml files
+    named by `jobs-from`.  The entities are read from mappings, and the
+    keys to those mappings are added in the `name` key of each entity.
+
+    If there is a `job-defaults` config, then every job is merged with it.
+    This provides a simple way to set default values for all jobs of a kind.
+    The `job-defaults` key can also be specified in a yaml file pointed to by
+    `jobs-from`. In this case it will only apply to tasks defined in the same
+    file.
+
+    Other kind implementations can use a different loader function to
+    produce inputs and hand them to `transform_inputs`.
+    """
+
+    def jobs():
+        defaults = config.get("job-defaults")
+        for name, job in six.iteritems(config.get("jobs", {})):
+            if defaults:
+                job = merge(defaults, job)
+            job["job-from"] = "kind.yml"
+            yield name, job
+
+        for filename in config.get("jobs-from", []):
+            tasks = load_yaml(path, filename)
+
+            file_defaults = tasks.pop("job-defaults", None)
+            if defaults:
+                file_defaults = merge(defaults, file_defaults or {})
+
+            for name, job in six.iteritems(tasks):
+                if file_defaults:
+                    job = merge(file_defaults, job)
+                job["job-from"] = filename
+                yield name, job
+
+    for name, job in jobs():
+        job["name"] = name
+        logger.debug("Generating tasks for {} {}".format(kind, name))
+        yield job