gh-104400: Add more tests to pygettext (GH-108173)

Lib/test/test_tools/i18n_data/messages.py

@@ -0,0 +1,64 @@
+# Test message extraction
+from gettext import gettext as _
+
+# Empty string
+_("")
+
+# Extra parentheses
+(_("parentheses"))
+((_("parentheses")))
+
+# Multiline strings
+_("Hello, "
+  "world!")
+
+_("""Hello,
+    multiline!
+""")
+
+# Invalid arguments
+_()
+_(None)
+_(1)
+_(False)
+_(x="kwargs are not allowed")
+_("foo", "bar")
+_("something", x="something else")
+
+# .format()
+_("Hello, {}!").format("world")  # valid
+_("Hello, {}!".format("world"))  # invalid
+
+# Nested structures
+_("1"), _("2")
+arr = [_("A"), _("B")]
+obj = {'a': _("A"), 'b': _("B")}
+{{{_('set')}}}
+
+
+# Nested functions and classes
+def test():
+    _("nested string")  # XXX This should be extracted but isn't.
+    [_("nested string")]
+
+
+class Foo:
+    def bar(self):
+        return _("baz")
+
+
+def bar(x=_('default value')):  # XXX This should be extracted but isn't.
+    pass
+
+
+def baz(x=[_('default value')]):  # XXX This should be extracted but isn't.
+    pass
+
+
+# Shadowing _()
+def _(x):
+    pass
+
+
+def _(x="don't extract me"):
+    pass