Fix TinyGo JSONBody[T] type-name collision - #24
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TinyGo's generic-function monomorphization keys plugin.JSONBody[T]
instantiations by T's bare type name rather than its full declaration
site. This package declared 8 locally-scoped `type bodyT struct{...}`
types across integration.go, branches.go, and pull_requests.go -- same
name, different fields per handler. TinyGo collapsed them into one
shared field layout, so json.Unmarshal silently decoded most call
sites against the wrong struct: fields came out zeroed with no error,
indistinguishable from an empty request body.
Renamed every JSONBody[T] body type to a name unique within the
package (e.g. setTokenBody, linkRepositoryBody). Verified by building
with the exact TinyGo version CI uses and driving the real binary
through the actual host runtime -- previously-broken routes now
correctly see their decoded fields.
Fixes Paca-AI/paca#445.
This was referenced Aug 30, 2026
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Summary
Fixes Paca-AI/paca#445 ("Plugin POST requests reach the WASM guest with an empty body").
The root cause is not in the
pacahost runtime (verified exhaustively — the WASM memory protocol and JSON envelope marshaling are correct). It's a TinyGo compiler behavior:plugin.JSONBody[T]is generic, and TinyGo's generic-function monomorphization appears to key instantiations byT's bare type name rather than its full declaration site.This package declared 8 locally-scoped
type bodyT struct{...}types acrossintegration.go,branches.go, andpull_requests.go— same name, different fields per handler (e.g.setToken's{Token string}vslinkRepository's{Owner, RepoName string}). TinyGo collapsed these into one shared field layout, sojson.Unmarshalsilently decoded most call sites against the wrong struct: fields came out zeroed with no error, indistinguishable from an empty request body.Fix
Renamed every
JSONBody[T]body type to a name unique within the package (setTokenBody,linkRepositoryBody,createBranchBody, etc.) — 8 renames across 3 files, no behavior changes otherwise.Verification
tinygo build -target=wasip1 -buildmode=c-shared, v0.41.1)services/api/internal/platform/plugin.Runtime), confirmingreq.Bodyarrives intact and previously-broken routes now correctly decode their fieldsgo test ./...andgo vet ./...passRelated
This same pattern (reused local type name across
JSONBody[T]call sites, broken by TinyGo) was found and fixed across all first-party plugins that switched to TinyGo builds: paca-plugin-bdd, paca-plugin-checklist, paca-plugin-dashboard, paca-plugin-example, paca-plugin-time-logging, paca-plugin-webhook.plugin-sdk-goalso got a non-genericJSONBodyIntohelper added as a documented escape hatch going forward.🤖 Generated with Claude Code