Python: False Positive on Global Type Variable

[cariad-robert-abel]

A globally defined type variable, usually a short-hand, is reported as being an unused global variable py/unused-global-variable, when it reality it's not, because it's used in a string type annotation.

Our code is closed source, so unfortunately a made up example will have illustrate the false positive:

from typing import TYPE_CHECKING

if TYPE_CHECKING:
    JiraIssue = dict[str, str]

def titlecase_jira_issues(issues: list['JiraIssue']):
    
    for issue in issues:
        issue['title'] = issue['title'].title()

In the snippet above, JiraIssue is reported as unused. We're using the codeql-bundle-v2.20.5/codeql-bundle-linux64.tar.zst.

The closest related issue I could find deals with a similar case involving unused imports, see #2042.

[mbg]

Hi @cariad-robert-abel 👋🏻

Thanks for reporting this! I have run this past the relevant engineering team and they confirm that support for string type annotations in Python is currently limited here. We will keep track of this issue internally. Although fixing false positives is not a current product priority and I cannot say how long it may take until this is fixed, the engineering team is working on a potential fix for this.