Method test_missing_expression

Lib/test/test_fstring.py:868–928

(self)

        self.assertEqual(f'{x} {x}', '1 2')

    def test_missing_expression(self):
        self.assertAllRaise(SyntaxError,
                            "f-string: valid expression required before '}'",
                            ["f'{}'",
                             "f'{ }'"
                             "f' {} '",
                             "f'{10:{ }}'",
                             "f' { } '",

                             # The Python parser ignores also the following
                             # whitespace characters in additional to a space.
                             "f'''{\t\f\r\n}'''",
                             ])

        self.assertAllRaise(SyntaxError,
                            "f-string: valid expression required before '!'",
                            ["f'{!r}'",
                             "f'{ !r}'",
                             "f'{!}'",
                             "f'''{\t\f\r\n!a}'''",

                             # Catch empty expression before the
                             #  missing closing brace.
                             "f'{!'",
                             "f'{!s:'",

                             # Catch empty expression before the
                             #  invalid conversion.
                             "f'{!x}'",
                             "f'{ !xr}'",
                             "f'{!x:}'",
                             "f'{!x:a}'",
                             "f'{ !xr:}'",
                             "f'{ !xr:a}'",
                             ])

        self.assertAllRaise(SyntaxError,
                            "f-string: valid expression required before ':'",
                            ["f'{:}'",
                             "f'{ :!}'",
                             "f'{:2}'",
                             "f'''{\t\f\r\n:a}'''",
                             "f'{:'",
                             "F'{[F'{:'}[F'{:'}]]]",
                             ])

        self.assertAllRaise(SyntaxError,
                            "f-string: valid expression required before '='",
                            ["f'{=}'",
                             "f'{ =}'",
                             "f'{ =:}'",
                             "f'{   =!}'",
                             "f'''{\t\f\r\n=}'''",
                             "f'{='",
                             ])

        # Different error message is raised for other whitespace characters.
        self.assertAllRaise(SyntaxError, r"invalid non-printable character U\+00A0",