def rust_datatypes_filter()

in glean_parser/rust.py [0:0]

• 45 lines of code
• 16 McCabe index (conditional complexity)

def rust_datatypes_filter(value):
    """
    A Jinja2 filter that renders Rust literals.

    Based on Python's JSONEncoder, but overrides:
      - dicts and sets to raise an error
      - sets to vec![] (used in labels)
      - enums to become Class::Value
      - lists to vec![] (used in send_in_pings)
      - null to None
      - strings to "value".into()
      - Rate objects to a CommonMetricData initializer
        (for external Denominators' Numerators lists)
    """

    class RustEncoder(json.JSONEncoder):
        def iterencode(self, value):
            if isinstance(value, dict):
                raise ValueError("RustEncoder doesn't know dicts {}".format(str(value)))
            elif isinstance(value, enum.Enum):
                yield (value.__class__.__name__ + "::" + util.Camelize(value.name))
            elif isinstance(value, set):
                yield "vec!["
                first = True
                for subvalue in sorted(list(value)):
                    if not first:
                        yield ", "
                    yield from self.iterencode(subvalue)
                    first = False
                yield "]"
            elif isinstance(value, list):
                yield "vec!["
                first = True
                for subvalue in list(value):
                    if not first:
                        yield ", "
                    yield from self.iterencode(subvalue)
                    first = False
                yield "]"
            elif value is None:
                yield "None"
            # `CowStr` is a `str`, so needs to be before next case
            elif isinstance(value, metrics.CowString):
                yield f'::std::borrow::Cow::from("{value.inner}")'
            elif isinstance(value, str):
                yield f"{json.dumps(value)}.into()"
            elif isinstance(value, metrics.Rate):
                yield "CommonMetricData("
                first = True
                for arg_name in util.common_metric_args:
                    if hasattr(value, arg_name):
                        if not first:
                            yield ", "
                        yield f"{util.camelize(arg_name)} = "
                        yield from self.iterencode(getattr(value, arg_name))
                        first = False
                yield ")"
            else:
                yield from super().iterencode(value)

    return "".join(RustEncoder().iterencode(value))