Fix -0.0 serialization for implicit-presence float and double fields

[timostamm]

With implicit presence (the proto3 default for singular scalar fields), the value decides whether a field is serialized:
false, "", and 0 are considered not set, and are omitted from the wire.

But there is a special case for float and double fields. The proto3 spec on Default Field Values:

If a float or double value is set to +0 it will not be serialized, but -0 is considered distinct and will be serialized.

We missed this detail. isScalarZeroValue from @bufbuild/protobuf/reflect treats -0.0 as a zero value, so a singular float or double field set to -0.0 is omitted during serialization, losing its sign in a round-trip.

This fixes the behavior to align with the spec. Note that this is a behavior change: -0.0 in a singular implicit-presence field is now written to the wire instead of omitted. The function equals inherits the fixed behavior for field presence, but float and double values are still compared with IEEE semantics: NaN does not equal NaN, and -0 equals 0.

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
protobuf-es	Ignored		Jun 19, 2026 3:33pm