codegen(go): Support JSON tags for nullable enum structs (#2121)

When `emit_json_tags` is set, add tags to nullable enum structs.

---------

Co-authored-by: Kyle Conroy <kyle@conroy.org>

Author: mikemherron

examples/batch/postgresql/models.go

@@ -17,6 +17,16 @@ type Enum struct {
 	Name      string
 	Comment   string
 	Constants []Constant
+	NameTags  map[string]string
+	ValidTags map[string]string
+}
+
+func (e Enum) NameTag() string {
+	return TagsToString(e.NameTags)
+}
+
+func (e Enum) ValidTag() string {
+	return TagsToString(e.ValidTags)
 }
 
 func EnumReplace(value string) string {

examples/ondeck/mysql/models.go

@@ -16,26 +16,30 @@ type Field struct {
 	Tags    map[string]string
 	Comment string
 	Column  *plugin.Column
-	// EmbedFields contains the embedded fields that reuqire scanning.
+	// EmbedFields contains the embedded fields that require scanning.
 	EmbedFields []string
 }
 
 func (gf Field) Tag() string {
-	tags := make([]string, 0, len(gf.Tags))
-	for key, val := range gf.Tags {
-		tags = append(tags, fmt.Sprintf("%s:\"%s\"", key, val))
-	}
-	if len(tags) == 0 {
-		return ""
-	}
-	sort.Strings(tags)
-	return strings.Join(tags, " ")
+	return TagsToString(gf.Tags)
 }
 
 func (gf Field) HasSqlcSlice() bool {
 	return gf.Column.IsSqlcSlice
 }
 
+func TagsToString(tags map[string]string) string {
+	if len(tags) == 0 {
+		return ""
+	}
+	tagParts := make([]string, 0, len(tags))
+	for key, val := range tags {
+		tagParts = append(tagParts, fmt.Sprintf("%s:\"%s\"", key, val))
+	}
+	sort.Strings(tagParts)
+	return strings.Join(tagParts, " ")
+}
+
 func JSONTagName(name string, settings *plugin.Settings) string {
 	style := settings.Go.JsonTagsCaseStyle
 	if style == "" || style == "none" {

examples/ondeck/postgresql/models.go

@@ -24,10 +24,18 @@ func buildEnums(req *plugin.CodeGenRequest) []Enum {
 			} else {
 				enumName = schema.Name + "_" + enum.Name
 			}
+
 			e := Enum{
-				Name:    StructName(enumName, req.Settings),
-				Comment: enum.Comment,
+				Name:      StructName(enumName, req.Settings),
+				Comment:   enum.Comment,
+				NameTags:  map[string]string{},
+				ValidTags: map[string]string{},
+			}
+			if req.Settings.Go.EmitJsonTags {
+				e.NameTags["json"] = JSONTagName(enumName, req.Settings)
+				e.ValidTags["json"] = JSONTagName("valid", req.Settings)
 			}
+
 			seen := make(map[string]struct{}, len(enum.Vals))
 			for i, v := range enum.Vals {
 				value := EnumReplace(v)

internal/codegen/golang/enum.go

@@ -88,8 +88,8 @@ func (e *{{.Name}}) Scan(src interface{}) error {
 }
 
 type Null{{.Name}} struct {
-	{{.Name}} {{.Name}}
-  Valid  bool // Valid is true if {{.Name}} is not NULL
+	{{.Name}} {{.Name}} {{if .NameTag}}{{$.Q}}{{.NameTag}}{{$.Q}}{{end}}
+  Valid  bool {{if .ValidTag}}{{$.Q}}{{.ValidTag}}{{$.Q}}{{end}} // Valid is true if {{.Name}} is not NULL
 }
 
 // Scan implements the Scanner interface.

internal/codegen/golang/field.go

@@ -0,0 +1,12 @@
+CREATE TYPE job_post_location_type AS ENUM('remote', 'in_office', 'hybrid');
+
+CREATE TABLE authors (
+    id   BIGSERIAL PRIMARY KEY,
+    type job_post_location_type,
+    name text      NOT NULL,
+    bio  text
+);
+
+-- name: GetAuthor :one
+SELECT * FROM authors
+WHERE id = $1 LIMIT 1;

internal/codegen/golang/result.go

@@ -0,0 +1,14 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "engine": "postgresql",
+      "name": "db",
+      "schema": "query.sql",
+      "queries": "query.sql",
+      "emit_json_tags": true,
+      "json_tags_case_style": "camel"
+    }
+  ]
+}