1 files changed, 114 insertions, 0 deletions
diff --git a/comm/taskcluster/comm_taskgraph/files_changed.py b/comm/taskcluster/comm_taskgraph/files_changed.py
new file mode 100644
index 0000000000..10deb65004
--- /dev/null
+++ b/comm/taskcluster/comm_taskgraph/files_changed.py
@@ -0,0 +1,114 @@
+# 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 taskgraph.util.memoize import memoize
+from taskgraph.util.path import join as join_path
+from taskgraph.util.path import match as match_path
+
+from gecko_taskgraph import GECKO
+from gecko_taskgraph.util.hg import get_json_automationrelevance
+from mozversioncontrol import InvalidRepoPath, get_repository_object
+
+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+        # We're likely on an unpublished commit, grab changed files from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 get_files_changed_extended(params):
+    """
+    Get the set of files changed in the push head from possibly multiple
+    head_repositories.
+    """
+    changed_files = set()
+
+    repo_keys = [key for key in params.keys() if key.endswith("head_repository")]
+
+    def prefix_changed(_changed, prefix):
+        if not prefix:
+            return _changed
+        else:
+            return {join_path(prefix, file) for file in _changed}
+
+    for repo_key in repo_keys:
+        repo_prefix = repo_key.replace("head_repository", "")
+        rev_key = f"{repo_prefix}head_rev"
+        repo_subdir_key = f"{repo_prefix}src_path"
+
+        repository = params.get(repo_key)
+        revision = params.get(rev_key)
+        repo_subdir = params.get(repo_subdir_key, "")
+
+        if not repository or not revision:
+            logger.warning(
+                f"Missing `{repo_key}` or `{rev_key}` parameters; "
+                "assuming all files have changed"
+            )
+            return True
+
+        changed_files |= prefix_changed(get_changed_files(repository, revision), repo_subdir)
+
+    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."""
+    changed_files = get_files_changed_extended(params)
+    if not changed_files:
+        logger.warning(
+            "changed_files from automationrelevance is empty; assuming all files have changed"
+        )
+        return True
+
+    for pattern in file_patterns:
+        for path in changed_files:
+            if match_path(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()