Enum KeyOnUnionDiscriminator 

pub enum KeyOnUnionDiscriminator {
    Refused,
    Carried,
}

Re-exported because ComposeOptions carries them in public fields, exactly as zerodds-idl-compose re-exports them: a caller that cannot name the type cannot construct the options. Whether @key on a union discriminator is carried into the model.

The clause permits it

DDS-XTypes 1.3 Table 21 lists @key against “Structure Members, Union discriminator”, and §7.2.2.4.4.4.8’s own example is

union MyCommand switch (@key CommandKind) { /* … */ };

so the default is to carry it: a front end that refuses the declaration, or tells the author the annotation “has no meaning” there, states the opposite of the specification.

What the implementations do

Measured on the four toolchains the Linux test host carries:

	union U switch (@key uint32)
Cyclone idlc	refuses the file — “Using union type as part of the key is currently unsupported”
rtiddsgen	refuses it at the discriminator — “@key is not supported”
fastddsgen	generates no PubSubType for a union at all, so it has no keyed topic to compare against
opendds_idl	not recorded in that run

So under Self::Carried this project computes a KeyHash over a union discriminator that no measured peer computes. Self::Refused is the setting for a tool that has to stay within what those toolchains accept; it names the clause that permits the declaration in its diagnostic.

Why the OMG suite needs it

union_uint32_one_key pairs unions.xml’s union_uint32 against unions_key_discriminator.xml’s union_uint32_key, whose discriminator carries key="true", and expects INCONSISTENT_TOPIC on both sides: §7.2.4.4.4.5 requires that “either the discriminators of both T1 and T2 are keys or neither are keys”. Under Self::Refused the subscriber never creates the topic and the case reports TOPIC_NOT_CREATED; under Self::Carried the declaration loads, the discriminator’s IS_KEY reaches its TypeObject, and the two types are found not assignable — which is the verdict the suite asks for.

A named type and not a bool for the reason HashedIdCounter is one: Options is Default, and a boolean defaulting to false would carry no statement about which reading that is.

Variants

Refused

The annotation is reported and the declaration does not carry it. What the measured toolchains do.

Carried

The annotation is carried: the model records it, the discriminator’s UnionDiscriminatorFlag gets IS_KEY, the union is a keyed topic type and its KeyHash is computed over the discriminator alone. The default, as Table 21 and §7.2.2.4.4.4.8 have it.

Implementations

impl KeyOnUnionDiscriminator

pub const ALL: [KeyOnUnionDiscriminator; 2]

Both.

pub const fn is_default(self) -> bool

Whether this is the default.

pub const fn as_str(self) -> &'static str

Short name, for configuration and diagnostics.

pub fn parse(value: &str) -> Option<KeyOnUnionDiscriminator>

Parse a configuration value.

An unknown value returns None rather than falling back to the default: a typo here changes a type’s TypeIdentifier.

Trait Implementations

impl Clone for KeyOnUnionDiscriminator

fn clone(&self) -> KeyOnUnionDiscriminator

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for KeyOnUnionDiscriminator

impl Debug for KeyOnUnionDiscriminator

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for KeyOnUnionDiscriminator

fn default() -> KeyOnUnionDiscriminator

Returns the “default value” for a type.

impl Eq for KeyOnUnionDiscriminator

impl PartialEq for KeyOnUnionDiscriminator

fn eq(&self, other: &KeyOnUnionDiscriminator) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for KeyOnUnionDiscriminator