Bug 1379163: make parameterization functions into utilities; r=bstack

These both have a similar form, recursing over a nested JSON structure, and are
useful outside of the modules in which they are defined.

MozReview-Commit-ID: 1bsRtlaQol7

taskcluster/taskgraph/util/parameterization.py

@@ -0,0 +1,48 @@
+# 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 re
+
+from taskgraph.util.time import json_time_from_now
+
+TASK_REFERENCE_PATTERN = re.compile('<([^>]+)>')
+
+
+def _recurse(val, param_name, param_fn):
+    param_keys = [param_name]
+
+    def recurse(val):
+        if isinstance(val, list):
+            return [recurse(v) for v in val]
+        elif isinstance(val, dict):
+            if val.keys() == param_keys:
+                return param_fn(val[param_name])
+            else:
+                return {k: recurse(v) for k, v in val.iteritems()}
+        else:
+            return val
+    return recurse(val)
+
+
+def resolve_timestamps(now, task_def):
+    """Resolve all instances of `{'relative-datestamp': '..'}` in the given task definition"""
+    return _recurse(task_def, 'relative-datestamp', lambda v: json_time_from_now(v, now))
+
+
+def resolve_task_references(label, task_def, dependencies):
+    """Resolve all instances of `{'task-reference': '..<..>..'}` in the given task
+    definition, using the given dependencies"""
+    def repl(match):
+        key = match.group(1)
+        try:
+            return dependencies[key]
+        except KeyError:
+            # handle escaping '<'
+            if key == '<':
+                return key
+            raise KeyError("task '{}' has no dependency named '{}'".format(label, key))
+
+    return _recurse(task_def, 'task-reference', lambda v: TASK_REFERENCE_PATTERN.sub(repl, v))