Function DiscriminatedChatMessagePart

scripts/apitypings/main.go:157–245

DiscriminatedChatMessagePart splits the flat ChatMessagePart interface into a discriminated union of per-type sub-interfaces. Each sub-interface narrows the `type` field to a string literal and includes only the fields relevant to that part type. Variant membership is declared via `variants` struct

(ts *guts.Typescript)

// ChatMessagePart fields in codersdk/chats.go. This function
// reads those tags via reflect and builds the union from them.
func DiscriminatedChatMessagePart(ts *guts.Typescript) {
	node, ok := ts.Node("ChatMessagePart")
	if !ok {
		return
	}
	iface, ok := node.(*bindings.Interface)
	if !ok {
		return
	}

	// Build a lookup from field name to its PropertySignature so
	// we can copy type information from the original interface.
	fieldMap := make(map[string]*bindings.PropertySignature, len(iface.Fields))
	for _, f := range iface.Fields {
		fieldMap[f.Name] = f
	}

	// copyField copies a field from the original interface into a
	// sub-interface, setting QuestionToken based on whether the
	// field is required for that variant.
	copyField := func(name string, required bool) *bindings.PropertySignature {
		orig, exists := fieldMap[name]
		if !exists {
			return nil
		}
		return &bindings.PropertySignature{
			Name:            orig.Name,
			Modifiers:       orig.Modifiers,
			QuestionToken:   !required,
			Type:            orig.Type,
			SupportComments: orig.SupportComments,
		}
	}

	variants := parseVariantTags()
	unionMembers := make([]bindings.ExpressionType, 0, len(variants))

	for _, v := range variants {
		fields := make([]*bindings.PropertySignature, 0, 1+len(v.required)+len(v.optional))

		// Discriminant field: type narrowed to a string literal.
		fields = append(fields, &bindings.PropertySignature{
			Name: "type",
			Type: &bindings.LiteralType{Value: string(v.typeLiteral)},
		})

		for _, name := range v.required {
			if f := copyField(name, true); f != nil {
				fields = append(fields, f)
			}
		}
		for _, name := range v.optional {
			if f := copyField(name, false); f != nil {
				fields = append(fields, f)
			}
		}

		tsName := chatMessagePartTSName(v.typeLiteral)