Union types in JDWP commands

[wekesa360]

This PR add the SetCommand from the Event Request Command Set.

[michalgr]

The modifiers field needs to be of type ArrayLength and outModifiers needs to be of an array type

[michalgr]

We want to use TaggedUnion type from schema.py to represent the union. This should look something like:

__SetCommand_outArray_Element_modKind = Field(
    "modKind",
    UnionTag(IntegralType.BYTE, ModifierKind),
    "Modifier kind",
)

__SetCommand_outArray_Element_Modifier = TaggedUnion(
    tag=__SetCommand_outArray_Element_modKind,
    cases={
        ModifierKind.COUNT: CountModifier,
        ModifierKind.CONDITIONAL: ConditionalModifier,
        ...
    },
)

In another PR we will want to enforce that the cases dict is total, for every possible enum value it has a corresponding Struct value. It can be done via a unit test :)

[michalgr]

To make this generic we want this to be a TypeVar that can be an arbitrary enum, not just ModifierKind. Would the following work ?

EnumT = TypeVar("M", bound=enum.Enum)

[michalgr]

Instead of specifying a particular value we should specify accepted range of values, ideally by specifying the enum class instead. Would this work ?

    value: Type[EnumT]

[michalgr]

We should make TaggedUnion generic over M/EnumT as well. How about something like this:

class TaggedUnion[Generic[EnumT]]:
    """Tagged Union class type"""

    tag: Field[UnionTag[EnumT]]
    cases: Mapping[EnumT, Struct]

Note that it's better to use collections.abc.Mapping than typing.Dict

[michalgr]

Could you rebase your PR ? These changes should not be in this PR

[michalgr]

Why do we need TaggedUnion here ?

[wekesa360]

I have worked on that, initially it was for the Array to accept the type TaggedUnion

[michalgr]

The type of the element of the array is a struct consisting of two fields: tag and tagged union

[wekesa360]

I have implemented the that, however the pyre checker is failing with:
Too many arguments [19]: Call `TaggedUnion.__init__` expects 0 positional arguments, 2 were provided.

looking at the TaggedUnion dataclass:

@dataclass(frozen=True)
class TaggedUnion:
    """Tagged Union class type"""

    tag: Field[UnionTag[EnumT]]
    cases: Mapping[EnumT, Struct]

And how tagged union is used is as:

TaggedUnion(
    tag=__SetCommand_out_modKind,
    cases={
        ModifierKind.COUNT: CountModifier,
        ModifierKind.CONDITIONAL: ConditionalModifier,
        ModifierKind.THREAD_ONLY: ThreadOnlyModifier,
        ModifierKind.CLASS_ONLY: ClassOnlyModifier,
        ModifierKind.CLASS_MATCH: ClassMatchModifier,
        ModifierKind.CLASS_EXCLUDE: ClassExcludeModifier,
        ModifierKind.STEP: StepModifier,
        ModifierKind.LOCATION_ONLY: LocationOnlyModifier,
        ModifierKind.EXCEPTION_ONLY: ExceptionOnlyModifier,
        ModifierKind.FIELD_ONLY: FieldOnlyModifier,
        ModifierKind.INSTANCE_ONLY: InstanceOnlyModifier,
        ModifierKind.SOURCE_NAME_MATCH: SourceNameMatchModifier,
    }
)

Would you kindly advice on how to resolve this fail.

[michalgr]

Yeah, I am not sure pyre got the definition of TaggedUnion right - I believe EnumT is not an allowed type unless you extend Generic[EnumT]

[michalgr]

Looks great already ! But there are three tiny comments left :)

[michalgr]

the order should be the other way around ?

[michalgr]

This needs to extend Generic[EnumT] as well