generate: set omitzero on specific types (#289)

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 +1,8 @@
 [[breaking]]
 title = "Update to Go 1.24"
 description = "Updated the SDK's Go version to Go 1.24. Consumers of this SDK will need to update to Go 1.24 as well. [#291](https://github.com/oxidecomputer/oxide.go/pull/291)"
+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 = ""

internal/generate/exceptions.go

@@ -4,6 +4,16 @@
 
 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",
+		"DerEncodedKeyPair",
+	}
+}
+
 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