Summary

The branch handling in test/compatibility/common/compatibility_version.py (WTVersion.{}init{}) is incorrect. It uses two separate if statements instead of an if/elif chain, and the else clause is attached only to the second if. As a result the "this" branch, one of the valid options, is rejected.

if name == "this":
    self.group = 2
if name == "develop":          # should be elif
    self.group = 1
else:
    # Match patterns like mongodb-8.0
    match = re.match(r'^mongodb-(\d+)\.(\d+)$', name)
    if match:
        self.major = int(match.group(1))
        self.minor = int(match.group(2))
    else:
        self.is_valid = False

When name == "this":

• The first if correctly sets group = 2.
• The second if name == "develop" is False, so it falls into its else, which runs the mongodb-X.Y regex against "this".
• The regex fails to match, so is_valid = False.

This makes the WT version "this" falsy (via bool) and rejects the this branch, which was supposed to be a valid option (it represents the code in the current folder, for which git checkout is skipped).

Fix

Change the second if to elif so the three cases (this, develop, mongodb-X.Y) are handled correctly:

if name == "this":
    self.group = 2
elif name == "develop":
    self.group = 1
else:
    match = re.match(r'^mongodb-(\d+)\.(\d+)$', name)
    ...