gh-133581: Improve AST unparsing of t-strings

[JelleZijlstra]

Fix unparsing of empty t-strings, and use the string value in unparsing interpolations.

• Issue: t-strings: AST unparsing does not reproduce original formatting #133581

[lysnikolaou]

LGTM! Thanks @JelleZijlstra! Let's backport this to 3.14 as well.

[miss-islington-app]

Thanks @JelleZijlstra for the PR 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-133666 is a backport of this pull request to the 3.14 branch.

[nascheme]

Looks like some refleak buildbots started failing after this.

https://buildbot.python.org/#/builders/1735/builds/6

test.test_future_stmt.test_future leaked [28, 28, 28] references, sum=84
test.test_future_stmt.test_future leaked [84, 84, 84] memory blocks, sum=252
Re-running test.test_future_stmt.test_future in verbose mode
test.test_future_stmt.test_future leaked [28, 28, 28] references, sum=84
test.test_future_stmt.test_future leaked [84, 84, 84] memory blocks, sum=252

[nascheme]

Yup, it bisects to this commit on the 3.14 branch:

commit 153496921a05e205d4c45c4a64888ccd43148897 (HEAD)
Author: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date:   Thu May 8 15:40:44 2025 +0200

    [3.14] gh-133581: Improve AST unparsing of t-strings (GH-133635) (#133666 

[JelleZijlstra]

Thanks for flagging, I'll investigate. Must be one of the changes in ast_unparse.c but from staring at the code I don't see anything wrong yet.

[JelleZijlstra]

Fix in #133724. The issue was in the existing code, it just wasn't tested before.