fix: omit proto3 implicit-presence defaults when encoding from parse().root

[spokodev]

A proto3 singular scalar set to its default value is incorrectly serialized onto the wire when the type is built via parse(proto).root or new Root().addJSON(json) and encoded without first calling resolveAll().

const M = protobuf.parse('syntax="proto3"; message M { int32 i32=1; string s=2; bool b=3; }')
  .root.lookupType("M");

M.encode({ i32: 0 }).finish()    // [8, 0]   — spec requires []
M.encode({ s: "" }).finish()     // [18, 0]  — spec requires []
M.encode({ b: false }).finish()  // [24, 0]  — spec requires []
M.encode({ i32: 5 }).finish()    // [8, 5]   — correct

Calling root.resolveAll() first (or using load()/loadSync()/fromJSON(), which resolve internally) produces the correct [], so only the lazy parse().root encode path is affected.

Cause

Type#setup() — the lazy initializer that builds the encoder on first encode() — resolves field types (field.resolve()) but never resolves feature defaults. So at codegen time field._features.field_presence is still undefined, and Field#hasPresence returns undefined !== "IMPLICIT" → true. The generated encoder then takes the presence-tracking branch (no default-value check) for an implicit-presence field and emits its default.

Impact

Non-canonical proto3 output from the most common inline-proto path: larger payloads, and byte-mismatches against peers that omit defaults (Go/C++/Python, and protobuf.js's own load()), which breaks deterministic serialization, signing/hashing of serialized bytes, and golden-file/conformance comparisons. Decoding is unaffected.

Fix

Resolve feature defaults in setup() before the codecs are generated — the same resolution load()/loadSync()/fromJSON() already perform — so parse().root produces the same wire form. Verified across syntaxes: proto3 implicit fields now omit defaults ([]); proto2, proto3 optional, and editions explicit-presence fields still emit them ([8,0]); -0.0 is still preserved.

Tests

Added a comp_optional case mirroring the existing "implicit scalar conversion defaults" test but without the resolveAll() call. It fails on the current code ([8,0]…) and passes with the fix. Full test:sources green (2723 passing, 0 failing); no regressions.

[dcodeIO]

Thanks!