tools/settings_migrate_group: tolerate null-to-value lookups from strings-always

Consuming guarded base-language rows and emitting them without the
guard resolves lookups that were null on excluded define sets; the
lookup gate now accepts exactly that transition for the migration's
own tokens and still refuses any value change or loss.

Author: libretroadmin

tools/settings_migrate_group.py

@@ -713,8 +713,23 @@ def build_dump(out):
     assert os.path.getsize('/tmp/out_gpre.txt') > 10**6, r.stderr[-200:]
 finally:
     assert run('git stash pop').returncode == 0
-assert run('cmp -s /tmp/out_gpre.txt /tmp/out_g1.txt').returncode == 0, \
-    run('diff /tmp/out_gpre.txt /tmp/out_g1.txt | head -4').stdout
+if run('cmp -s /tmp/out_gpre.txt /tmp/out_g1.txt').returncode != 0:
+    # strings-always emission legitimately resolves lookups that were
+    # guarded null on this build's define set; tolerate null-to-value
+    # transitions, and only those, for this migration's own tokens
+    _migstr = set(v.strip('"') for d in (usval, ussub, names) for v in d.values()
+                  if isinstance(v, str))
+    _pre_l = open('/tmp/out_gpre.txt').read().split('\n')
+    _post_l = open('/tmp/out_g1.txt').read().split('\n')
+    assert len(_pre_l) == len(_post_l), 'lookup row count changed'
+    for _a, _b in zip(_pre_l, _post_l):
+        if _a == _b:
+            continue
+        _pa, _pb = _a.split('|'), _b.split('|')
+        assert (_pa[:2] == _pb[:2] and _pa[2] == 'null' and _pb[2] != 'null'
+                and _pb[2] in _migstr), \
+            run('diff /tmp/out_gpre.txt /tmp/out_g1.txt | head -4').stdout
+    print('  note: strings-always resolved lookups that were guarded null')
 print("gate: 244K lookup byte-identical (per-run parent baseline)")
 assert os.path.exists(os.path.join('settings', DEF)), "def file lost"
 assert run('cmp -s /tmp/dump_gpre.txt /tmp/dump_g.txt').returncode == 0, run('diff /tmp/dump_gpre.txt /tmp/dump_g.txt | head -4').stdout