1 files changed, 93 insertions, 0 deletions
diff --git a/taskcluster/taskgraph/transforms/base.py b/taskcluster/taskgraph/transforms/base.py
new file mode 100644
index 0000000000..fee4bda774
--- /dev/null
+++ b/taskcluster/taskgraph/transforms/base.py
@@ -0,0 +1,93 @@
+# 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 attr
+from six import text_type
+
+from ..config import GraphConfig
+from ..parameters import Parameters
+from ..util.schema import Schema, validate_schema
+
+
+@attr.s(frozen=True)
+class TransformConfig(object):
+    """
+    A container for configuration affecting transforms.  The `config` argument
+    to transforms is an instance of this class.
+    """
+
+    # the name of the current kind
+    kind = attr.ib()
+
+    # the path to the kind configuration directory
+    path = attr.ib(type=text_type)
+
+    # the parsed contents of kind.yml
+    config = attr.ib(type=dict)
+
+    # the parameters for this task-graph generation run
+    params = attr.ib(type=Parameters)
+
+    # a list of all the tasks associated with the kind dependencies of the
+    # current kind
+    kind_dependencies_tasks = attr.ib()
+
+    # Global configuration of the taskgraph
+    graph_config = attr.ib(type=GraphConfig)
+
+    # whether to write out artifacts for the decision task
+    write_artifacts = attr.ib(type=bool)
+
+
+@attr.s()
+class TransformSequence(object):
+    """
+    Container for a sequence of transforms.  Each transform is represented as a
+    callable taking (config, items) and returning a generator which will yield
+    transformed items.  The resulting sequence has the same interface.
+
+    This is convenient to use in a file full of transforms, as it provides a
+    decorator, @transforms.add, that will add the decorated function to the
+    sequence.
+    """
+
+    _transforms = attr.ib(factory=list)
+
+    def __call__(self, config, items):
+        for xform in self._transforms:
+            items = xform(config, items)
+            if items is None:
+                raise Exception("Transform {} is not a generator".format(xform))
+        return items
+
+    def add(self, func):
+        self._transforms.append(func)
+        return func
+
+    def add_validate(self, schema):
+        self.add(ValidateSchema(schema))
+
+
+@attr.s
+class ValidateSchema(object):
+    schema = attr.ib(type=Schema)
+
+    def __call__(self, config, tasks):
+        for task in tasks:
+            if "name" in task:
+                error = "In {kind} kind task {name!r}:".format(
+                    kind=config.kind, name=task["name"]
+                )
+            elif "label" in task:
+                error = "In job {label!r}:".format(label=task["label"])
+            elif "primary-dependency" in task:
+                error = "In {kind} kind task for {dependency!r}:".format(
+                    kind=config.kind, dependency=task["primary-dependency"].label
+                )
+            else:
+                error = "In unknown task:"
+            validate_schema(self.schema, task, error)
+            yield task