git_llvm_rev: auto-update llvm-project-copy in tests

My local llvm-project-copy was out-of-date. It's nice if we can
automatically handle that.

This also fixes lints and such that weren't able to fire when this was
originally landed.

BUG=chromium:1041016
TEST=Wiped out my LLVM tree; it synced without issue. Tried syncing with
     a timedelta of seconds=2; everything WAI.

Change-Id: I4a4811bb1500db0b00c924eec0be12dc57499fc6
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/toolchain-utils/+/1995316
Reviewed-by: Manoj Gupta <manojgupta@chromium.org>
Tested-by: George Burgess <gbiv@chromium.org>

2 files changed, 47 insertions, 11 deletions

diff --git a/llvm_tools/git_llvm_rev.py b/llvm_tools/git_llvm_rev.py
index 793b56f9..8eefcdce 100755
--- a/llvm_tools/git_llvm_rev.py
+++ b/llvm_tools/git_llvm_rev.py
@@ -10,6 +10,8 @@ Revision numbers are all of the form '(branch_name, r1234)'. As a shorthand,
 r1234 is parsed as '(master, 1234)'.
 """
 
+from __future__ import print_function
+
 import argparse
 import re
 import subprocess
@@ -184,8 +186,7 @@ def translate_sha_to_rev(llvm_config: LLVMConfig, sha_or_ref: str) -> Rev:
         f'Ambiguity: multiple branches from {llvm_config.remote} have {sha}: '
         f'{sorted(candidates)}')
 
-  branch, = candidates
-  return Rev(branch=branch, number=revision_number)
+  return Rev(branch=candidates[0], number=revision_number)
 
 
 def parse_git_commit_messages(stream: t.Iterable[str],
@@ -208,6 +209,8 @@ def parse_git_commit_messages(stream: t.Iterable[str],
 
   lines = iter(stream)
   while True:
+    # Looks like a potential bug in pylint? crbug.com/1041148
+    # pylint: disable=stop-iteration-return
     sha = next(lines, None)
     if sha is None:
       return
diff --git a/llvm_tools/git_llvm_rev_test.py b/llvm_tools/git_llvm_rev_test.py
index 06b83cd1..c7d59b27 100755
--- a/llvm_tools/git_llvm_rev_test.py
+++ b/llvm_tools/git_llvm_rev_test.py
@@ -8,10 +8,13 @@
 
 from __future__ import print_function
 
+import datetime
 import os
+import subprocess
 import sys
 import unittest
 
+import get_llvm_hash
 import git_llvm_rev
 
 
@@ -20,6 +23,44 @@ def get_llvm_checkout() -> str:
   return os.path.join(my_dir, 'llvm-project-copy')
 
 
+def ensure_llvm_project_up_to_date():
+  checkout = get_llvm_checkout()
+  if not os.path.isdir(checkout):
+    print(
+        'No llvm-project exists locally; syncing it. This takes a while.',
+        file=sys.stderr)
+    actual_checkout = get_llvm_hash.GetAndUpdateLLVMProjectInLLVMTools()
+    assert checkout == actual_checkout, '%s != %s' % (actual_checkout, checkout)
+
+  commit_timestamp = git_llvm_rev.check_output(
+      ['git', 'log', '-n1', '--format=%ct', 'origin/master'], cwd=checkout)
+
+  commit_time = datetime.datetime.fromtimestamp(int(commit_timestamp.strip()))
+  now = datetime.datetime.now()
+
+  time_since_last_commit = now - commit_time
+
+  # Arbitrary, but if it's been more than 2d since we've seen a commit, it's
+  # probably best to bring us up-to-date.
+  if time_since_last_commit <= datetime.timedelta(days=2):
+    return
+
+  print(
+      '%d days have elapsed since the last commit to %s; auto-syncing' %
+      (time_since_last_commit.days, checkout),
+      file=sys.stderr)
+
+  result = subprocess.run(
+      ['git', 'fetch', 'origin'],
+      cwd=checkout,
+      check=True,
+  )
+  if result.returncode:
+    print(
+        'Sync failed somehow; hoping that things are fresh enough, then...',
+        file=sys.stderr)
+
+
 def get_llvm_config() -> git_llvm_rev.LLVMConfig:
   return git_llvm_rev.LLVMConfig(dir=get_llvm_checkout(), remote='origin')
 
@@ -131,13 +172,5 @@ class Test(unittest.TestCase):
 # back to the base commit for.
 
 if __name__ == '__main__':
-  # We have exactly one concrete target that we often have checked out anyway.
-  # Rather than building tests that hopefully match that target, use it
-  # directly.
-  if not os.path.isdir(get_llvm_checkout()):
-    print(
-        'Please checkout llvm-project-copy to run these tests. A simple way '
-        'to do that is running `./get_llvm_hash.py --llvm_version 370000`',
-        file=sys.stderr)
-    sys.exit(1)
+  ensure_llvm_project_up_to_date()
   unittest.main()