Files
go-telegram/cmd/genapi/types.tmpl
T
lukaszraczylo 370c9c0802 refactor(api): auto-inject discriminator value via generated MarshalJSON
Sealed-interface union variants now hardcode their wire discriminator
inside a generated MarshalJSON method instead of forcing callers to set
the field on every struct literal. Drops a class of silent-rejection
bugs where a typo in the discriminator slipped past the type checker
and through to Telegram, which then rejected the request with no
Go-side signal.

The discriminator field stays exported so incoming-message decoding,
type switches and debugging still see it. MarshalJSON wraps via a
function-local type alias and emits an outer field with the same json
tag; encoding/json (and goccy/go-json) resolve the outer field as the
shallower one and override whatever the caller wrote.

99 variants get MarshalJSON. 7 are skipped because their unions
dispatch structurally rather than by a string field: Message and
InaccessibleMessage (MaybeInaccessibleMessage, dispatched on date),
and the InputMessageContent family (InputTextMessageContent,
InputLocationMessageContent, InputVenueMessageContent,
InputContactMessageContent, InputInvoiceMessageContent — Telegram
identifies these by the presence of message_text / latitude /
phone_number / title etc.).

Discriminator extraction lives in the emitter (cmd/genapi/emitter.go).
Resolution: knownDiscriminators reverse-lookup for the 13 auto-decode
unions, then doc-string analysis ("must be X" / "always “X”")
of the variant's first required string field for marker-only unions
(BotCommandScope, InputMedia, InputPaidMedia, InputProfilePhoto,
InputStoryContent, InputPollMedia, InputPollOptionMedia,
InlineQueryResult, PassportElementError). Variants the emitter cannot
resolve a discriminator for are skipped silently rather than emitting
broken code.

Internal call-site cleanups: 4 manual discriminator assignments
removed (api/unionparam_test.go,
dispatch/filters/message/message_test.go, examples/inline/main.go ×2).
Regression tests added in api/marshaljson_variants_test.go covering
type-keyed variants, source-keyed variants, the override-user-typo
guarantee, round-trip preservation through UnmarshalChatMember, the
no-discriminator InputMessageContent path, and ride-along of
non-discriminator fields.

regen-from-fixture is deterministic across two consecutive runs;
go test -race / go vet / staticcheck all clean.
2026-05-09 19:27:33 +01:00

144 lines
4.4 KiB
Cheetah

// Code generated by cmd/genapi. DO NOT EDIT.
//go:build !ignore_autogenerated
// Package api contains the Telegram Bot API object types and method
// wrappers, generated from the live documentation by cmd/genapi.
package api
import (
"github.com/goccy/go-json"
"fmt"
"io"
)
var _ = io.Discard // keep import even if no fields use io
var _ = json.Marshal // keep import for UnmarshalXxx helpers
var _ = fmt.Errorf // keep import for UnmarshalXxx helpers
{{range .Types}}
{{- $td := . -}}
{{if .OneOf}}
// {{.Name}} is a union type. The following concrete variants implement
// it:
{{range .OneOf}}// - {{.}}
{{end}}//
{{docComment .Doc -}}
type {{.Name}} interface{ is{{.Name}}() }
{{range .OneOf}}
// is{{$td.Name}} is the marker method that makes {{.}} implement {{$td.Name}}.
func (*{{.}}) is{{$td.Name}}() {}
{{end}}
{{if hasDiscriminator .Name}}
// Unmarshal{{.Name}} decodes a {{.Name}} from JSON by inspecting the
// "{{discriminatorField .Name}}" field and dispatching to the correct concrete type.
func Unmarshal{{.Name}}(data []byte) ({{.Name}}, error) {
var probe struct {
V string `json:"{{discriminatorField .Name}}"`
}
if err := json.Unmarshal(data, &probe); err != nil {
return nil, err
}
var v {{.Name}}
switch probe.V {
{{range $val, $typ := discriminatorMap .Name}} case {{printf "%q" $val}}:
v = &{{$typ}}{}
{{end}} default:
return nil, fmt.Errorf("{{.Name}}: unknown {{discriminatorField .Name}} %q", probe.V)
}
if err := json.Unmarshal(data, v); err != nil {
return nil, err
}
return v, nil
}
{{end}}
{{if isMaybeInaccessibleMessage .Name}}
// UnmarshalMaybeInaccessibleMessage decodes a JSON object into the correct
// MaybeInaccessibleMessage variant. Telegram uses the date field as a
// discriminator: date == 0 indicates InaccessibleMessage; any other value
// indicates a real Message.
func UnmarshalMaybeInaccessibleMessage(data []byte) (MaybeInaccessibleMessage, error) {
var probe struct {
Date int64 `json:"date"`
}
if err := json.Unmarshal(data, &probe); err != nil {
return nil, fmt.Errorf("MaybeInaccessibleMessage: %w", err)
}
if probe.Date == 0 {
v := &InaccessibleMessage{}
if err := json.Unmarshal(data, v); err != nil {
return nil, fmt.Errorf("InaccessibleMessage: %w", err)
}
return v, nil
}
v := &Message{}
if err := json.Unmarshal(data, v); err != nil {
return nil, fmt.Errorf("Message: %w", err)
}
return v, nil
}
{{end}}
{{else}}
{{docComment .Doc -}}
type {{.Name}} struct {
{{range .Fields}}{{docComment .Doc}}{{goField $td.Name .}}
{{end}}}
{{if variantHasDisc .Name}}
// MarshalJSON encodes {{.Name}} with the discriminator field
// "{{variantDiscField .Name}}" forced to {{printf "%q" (variantDiscValue .Name)}}.
// The hardcoded value frees callers from setting {{variantDiscGoField .Name}} by hand —
// any user-supplied value on the struct literal is overridden so a typo
// can't slip through to Telegram.
func (v *{{.Name}}) MarshalJSON() ([]byte, error) {
type alias {{.Name}}
return json.Marshal(&struct {
{{variantDiscGoField .Name}} string `json:"{{variantDiscField .Name}}"`
*alias
}{
{{variantDiscGoField .Name}}: {{printf "%q" (variantDiscValue .Name)}},
alias: (*alias)(v),
})
}
{{end}}
{{$unionFields := unionFields .}}{{if $unionFields}}
// UnmarshalJSON decodes {{.Name}} by dispatching union-typed fields
// ({{range $i, $u := $unionFields}}{{if $i}}, {{end}}{{$u.Field.Name}}{{end}}) through their concrete UnmarshalXxx helpers.
func (m *{{.Name}}) UnmarshalJSON(data []byte) error {
type Alias {{.Name}}
aux := &struct {
{{range $unionFields}}{{.Field.Name}} json.RawMessage `json:"{{.Field.JSONName}},omitempty"`
{{end}}*Alias
}{Alias: (*Alias)(m)}
if err := json.Unmarshal(data, aux); err != nil {
return err
}
{{range $unionFields}}{{$f := .Field}}{{$u := .UnionName}}
if len(aux.{{$f.Name}}) > 0 && string(aux.{{$f.Name}}) != "null" {
{{if isArrayUnion $f.Type}}var raws []json.RawMessage
if err := json.Unmarshal(aux.{{$f.Name}}, &raws); err != nil {
return fmt.Errorf("decoding {{$f.JSONName}}: %w", err)
}
decoded := make([]{{$u}}, 0, len(raws))
for i, r := range raws {
v, err := Unmarshal{{$u}}(r)
if err != nil {
return fmt.Errorf("decoding {{$f.JSONName}}[%d]: %w", i, err)
}
decoded = append(decoded, v)
}
m.{{$f.Name}} = decoded
{{else}}v, err := Unmarshal{{$u}}(aux.{{$f.Name}})
if err != nil {
return fmt.Errorf("decoding {{$f.JSONName}}: %w", err)
}
m.{{$f.Name}} = v
{{end}}
}
{{end}}
return nil
}
{{end}}
{{end}}
{{end}}