1 files changed, 95 insertions, 0 deletions
diff --git a/taskcluster/gecko_taskgraph/files_changed.py b/taskcluster/gecko_taskgraph/files_changed.py
new file mode 100644
index 0000000000..c814df0806
--- /dev/null
+++ b/taskcluster/gecko_taskgraph/files_changed.py
@@ -0,0 +1,95 @@
+# 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/.
+
+"""
+Support for optimizing tasks based on the set of files that have changed.
+"""
+
+import logging
+import os
+from subprocess import CalledProcessError
+
+from mozbuild.util import memoize
+from mozpack.path import join as join_path
+from mozpack.path import match as mozpackmatch
+from mozversioncontrol import InvalidRepoPath, get_repository_object
+
+from gecko_taskgraph import GECKO
+from gecko_taskgraph.util.hg import get_json_automationrelevance
+
+logger = logging.getLogger(__name__)
+
+
+@memoize
+def get_changed_files(repository, revision):
+    """
+    Get the set of files changed in the push headed by the given revision.
+    Responses are cached, so multiple calls with the same arguments are OK.
+    """
+    contents = get_json_automationrelevance(repository, revision)
+    try:
+        changesets = contents["changesets"]
+    except KeyError:
+        # We shouldn't hit this error in CI.
+        if os.environ.get("MOZ_AUTOMATION"):
+            raise
+
+        # We're likely on an unpublished commit, grab changed files from
+        # version control.
+        return get_locally_changed_files(GECKO)
+
+    logger.debug("{} commits influencing task scheduling:".format(len(changesets)))
+    changed_files = set()
+    for c in changesets:
+        desc = ""  # Support empty desc
+        if c["desc"]:
+            desc = c["desc"].splitlines()[0].encode("ascii", "ignore")
+        logger.debug(" {cset} {desc}".format(cset=c["node"][0:12], desc=desc))
+        changed_files |= set(c["files"])
+
+    return changed_files
+
+
+def check(params, file_patterns):
+    """Determine whether any of the files changed in the indicated push to
+    https://hg.mozilla.org match any of the given file patterns."""
+    repository = params.get("head_repository")
+    revision = params.get("head_rev")
+    if not repository or not revision:
+        logger.warning(
+            "Missing `head_repository` or `head_rev` parameters; "
+            "assuming all files have changed"
+        )
+        return True
+
+    changed_files = get_changed_files(repository, revision)
+
+    if "comm_head_repository" in params:
+        repository = params.get("comm_head_repository")
+        revision = params.get("comm_head_rev")
+        if not revision:
+            logger.warning(
+                "Missing `comm_head_rev` parameters; " "assuming all files have changed"
+            )
+            return True
+
+        changed_files |= {
+            join_path("comm", file) for file in get_changed_files(repository, revision)
+        }
+
+    for pattern in file_patterns:
+        for path in changed_files:
+            if mozpackmatch(path, pattern):
+                return True
+
+    return False
+
+
+@memoize
+def get_locally_changed_files(repo):
+    try:
+        vcs = get_repository_object(repo)
+        return set(vcs.get_outgoing_files("AM"))
+    except (InvalidRepoPath, CalledProcessError):
+        return set()