Method check_specs_in_format_call

mypy/checkstrformat.py:333–404

Perform pairwise checks for conversion specifiers vs their replacements. The core logic for format checking is implemented in this method.

(
        self, call: CallExpr, specs: list[ConversionSpecifier], format_value: str
    )

        self.check_specs_in_format_call(call, conv_specs, format_value)

    def check_specs_in_format_call(
        self, call: CallExpr, specs: list[ConversionSpecifier], format_value: str
    ) -> None:
        """Perform pairwise checks for conversion specifiers vs their replacements.

        The core logic for format checking is implemented in this method.
        """
        assert all(s.key for s in specs), "Keys must be auto-generated first!"
        replacements = self.find_replacements_in_call(call, [cast(str, s.key) for s in specs])
        assert len(replacements) == len(specs)
        for spec, repl in zip(specs, replacements):
            repl = self.apply_field_accessors(spec, repl, ctx=call)
            actual_type = repl.type if isinstance(repl, TempNode) else self.chk.lookup_type(repl)
            assert actual_type is not None

            # Special case custom formatting.
            if (
                spec.format_spec
                and spec.non_standard_format_spec
                and
                # Exclude "dynamic" specifiers (i.e. containing nested formatting).
                not ("{" in spec.format_spec or "}" in spec.format_spec)
            ):
                if (
                    not custom_special_method(actual_type, "__format__", check_all=True)
                    or spec.conversion
                ):
                    # TODO: add support for some custom specs like datetime?
                    self.msg.fail(
                        f'Unrecognized format specification "{spec.format_spec[1:]}"',
                        call,
                        code=codes.STRING_FORMATTING,
                    )
                    continue
            # Adjust expected and actual types.
            if not spec.conv_type:
                expected_type: Type | None = AnyType(TypeOfAny.special_form)
            else:
                assert isinstance(call.callee, MemberExpr)
                if isinstance(call.callee.expr, StrExpr):
                    format_str = call.callee.expr
                else:
                    format_str = StrExpr(format_value)
                expected_type = self.conversion_type(
                    spec.conv_type, call, format_str, format_call=True
                )
            if spec.conversion is not None:
                # If the explicit conversion is given, then explicit conversion is called _first_.
                if spec.conversion[1] not in "rsa":
                    self.msg.fail(
                        (
                            f'Invalid conversion type "{spec.conversion[1]}", '
                            f'must be one of "r", "s" or "a"'
                        ),
                        call,
                        code=codes.STRING_FORMATTING,
                    )
                actual_type = self.named_type("builtins.str")