1 files changed, 109 insertions, 0 deletions
diff --git a/taskcluster/taskgraph/task/transform.py b/taskcluster/taskgraph/task/transform.py
new file mode 100644
index 000000000..8183254a0
--- /dev/null
+++ b/taskcluster/taskgraph/task/transform.py
@@ -0,0 +1,109 @@
+# 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 itertools
+
+from . import base
+from .. import files_changed
+from ..util.python_path import find_object
+from ..util.templates import merge
+from ..util.yaml import load_yaml
+from ..util.seta import is_low_value_task
+
+from ..transforms.base import TransformSequence, TransformConfig
+
+logger = logging.getLogger(__name__)
+
+
+class TransformTask(base.Task):
+    """
+    Tasks of this class are generated by applying transformations to a sequence
+    of input entities.  By default, it gets those inputs from YAML data in the
+    kind directory, but subclasses may override `get_inputs` to produce them in
+    some other way.
+    """
+
+    @classmethod
+    def get_inputs(cls, kind, path, config, params, loaded_tasks):
+        """
+        Get the input elements that will be transformed into tasks.  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.  More complex defaults should be implemented with custom
+        transforms.
+
+        This method can be overridden in subclasses that need to perform more
+        complex calculations to generate the list of inputs.
+        """
+        def jobs():
+            defaults = config.get('job-defaults')
+            jobs = config.get('jobs', {}).iteritems()
+            jobs_from = itertools.chain.from_iterable(
+                load_yaml(path, filename).iteritems()
+                for filename in config.get('jobs-from', {}))
+            for name, job in itertools.chain(jobs, jobs_from):
+                if defaults:
+                    job = merge(defaults, job)
+                yield name, job
+
+        for name, job in jobs():
+            job['name'] = name
+            logger.debug("Generating tasks for {} {}".format(kind, name))
+            yield job
+
+    @classmethod
+    def load_tasks(cls, kind, path, config, params, loaded_tasks):
+        inputs = cls.get_inputs(kind, path, config, params, loaded_tasks)
+
+        transforms = TransformSequence()
+        for xform_path in config['transforms']:
+            transform = find_object(xform_path)
+            transforms.add(transform)
+
+        # perform the transformations
+        trans_config = TransformConfig(kind, path, config, params)
+        tasks = [cls(kind, t) for t in transforms(trans_config, inputs)]
+        return tasks
+
+    def __init__(self, kind, task):
+        self.dependencies = task['dependencies']
+        self.when = task['when']
+        super(TransformTask, self).__init__(kind, task['label'],
+                                            task['attributes'], task['task'])
+
+    def get_dependencies(self, taskgraph):
+        return [(label, name) for name, label in self.dependencies.items()]
+
+    def optimize(self, params):
+        if 'files-changed' in self.when:
+            changed = files_changed.check(
+                params, self.when['files-changed'])
+            if not changed:
+                logger.debug('no files found matching a pattern in `when.files-changed` for ' +
+                             self.label)
+                return True, None
+
+        # we would like to return 'False, None' while it's high_value_task
+        # and we wouldn't optimize it. Otherwise, it will return 'True, None'
+        if is_low_value_task(self.label, params.get('project')):
+            # Always optimize away low-value tasks
+            return True, None
+        else:
+            return False, None
+
+    @classmethod
+    def from_json(cls, task_dict):
+        # when reading back from JSON, we lose the "when" information
+        task_dict['when'] = {}
+        return cls(task_dict['attributes']['kind'], task_dict)