generate: set omitzero on specific types

Set `omitzero` on the following types to allow clients to set an empty
slice and have it serialized to `[]`, which is required by Oxide APIs to
unset a value.

* `[]VpcFirewallRuleUpdate`
* `[]NameOrId`

The previous behavior would omit an empty slice entirely during
serialization, causing the Oxide APIs to respond with an error.

Author: sudomateo

.changelog/v0.5.0.toml

@@ -1,6 +1,6 @@
 [[breaking]]
-title = ""
-description = ""
+title = "Set `omitzero` on specific types"
+description = "Set `omitzero` on specific types so that clients can pass an empty slice and have it serialized as `[]`. Requires Go 1.24 or later. [#289](https://github.com/oxidecomputer/oxide.go/pull/289)"
 
 [[features]]
 title = ""
@@ -12,4 +12,4 @@ description = "All arrays that are nullable in the API no longer have `omitempty
 
 [[enhancements]]
 title = ""
-description = ""
+description = ""

go.mod

@@ -1,6 +1,6 @@
 module github.com/oxidecomputer/oxide.go
 
-go 1.22.5
+go 1.24.3
 
 require (
 	github.com/getkin/kin-openapi v0.132.0

internal/generate/exceptions.go

@@ -4,6 +4,15 @@
 
 package main
 
+// omitzeroTypes returns a slice of types that should be tagged with omitzero
+// for serialization and deserialization.
+func omitzeroTypes() []string {
+	return []string{
+		"[]VpcFirewallRuleUpdate",
+		"[]NameOrId",
+	}
+}
+
 func emptyTypes() []string {
 	return []string{
 		"BgpMessageHistory",

internal/generate/types.go

@@ -542,9 +542,13 @@ func createTypeObject(schema *openapi3.Schema, name, typeName, description strin
 		field.Name = strcase.ToCamel(k)
 		field.Type = typeName
 
+		// TODO: Set omitzero on all types.
+		// https://github.com/oxidecomputer/oxide.go/issues/290
 		serInfo := fmt.Sprintf("`json:\"%s,omitempty\" yaml:\"%s,omitempty\"`", k, k)
 		if isNullableArray(v) {
 			serInfo = fmt.Sprintf("`json:\"%s\" yaml:\"%s\"`", k, k)
+		} else if sliceContains(omitzeroTypes(), typeName) {
+			serInfo = fmt.Sprintf("`json:\"%s,omitzero\" yaml:\"%s,omitzero\"`", k, k)
 		}
 
 		field.SerializationInfo = serInfo