feat(codegen): generate json struct tags with omitempty (#246)

pkg/codegen/generators/helpers.go

@@ -5,6 +5,7 @@ import (
 	"strings"
 
 	"github.com/lerenn/asyncapi-codegen/pkg/asyncapi"
+	"github.com/lerenn/asyncapi-codegen/pkg/utils/template"
 )
 
 func appendDirectiveIfDefined(directives []string, tagName string, value float64) []string {
@@ -14,6 +15,19 @@ func appendDirectiveIfDefined(directives []string, tagName string, value float64
 	return directives
 }
 
+// GenerateJSONTags returns the "json" tag for a given field in a struct, based on the asyncapi contract.
+func GenerateJSONTags[T any](schema asyncapi.Validations[T], field string) string {
+	directives := []string{
+		template.ConvertKey(field),
+	}
+
+	if !schema.IsRequired {
+		directives = append(directives, "omitempty")
+	}
+
+	return fmt.Sprintf("json:\"%s\"", strings.Join(directives, ","))
+}
+
 // GenerateValidateTags returns the "validate" tag for a given field in a struct, based on the asyncapi contract.
 // This tag can then be used by go-playground/validator/v10 to validate the struct's content.
 func GenerateValidateTags[T any](schema asyncapi.Validations[T]) string {

pkg/codegen/generators/v2/templates/helpers.go

@@ -153,5 +153,6 @@ func HelpersFunctions() template.FuncMap {
 		"operationName":                  OperationName,
 		"referenceToTypeName":            ReferenceToTypeName,
 		"generateValidateTags":           generators.GenerateValidateTags[asyncapi.Schema],
+		"generateJSONTags":               generators.GenerateJSONTags[asyncapi.Schema],
 	}
 }

pkg/codegen/generators/v2/templates/schema_definition.tmpl

@@ -15,7 +15,7 @@ type {{ namify .Name }} struct {
     {{else if and $value.ReferenceTo $value.ReferenceTo.Description}}
     // Description: {{multiLineComment $value.ReferenceTo.Description}}
     {{end -}}
-    {{namify $key}} {{if and (not (isRequired $ $key)) (ne $value.Type "array")}}*{{end}}{{template "schema-name" $value}} `json:"{{convertKey $key}}"{{generateValidateTags $value.Validations}}`
+    {{namify $key}} {{if and (not (isRequired $ $key)) (ne $value.Type "array")}}*{{end}}{{template "schema-name" $value}} `{{generateJSONTags $value.Validations $key}}{{generateValidateTags $value.Validations}}`
     {{end -}}
 
     {{- if .AdditionalProperties}}

pkg/codegen/generators/v3/templates/helpers.go

@@ -140,5 +140,6 @@ func HelpersFunctions() template.FuncMap {
 		"generateChannelAddrFromOp":      GenerateChannelAddrFromOp,
 		"referenceToStructAttributePath": ReferenceToStructAttributePath,
 		"generateValidateTags":           generators.GenerateValidateTags[asyncapi.Schema],
+		"generateJSONTags":               generators.GenerateJSONTags[asyncapi.Schema],
 	}
 }

pkg/codegen/generators/v3/templates/schema_definition.tmpl

@@ -15,7 +15,7 @@ type {{ namify .Name }} struct {
     {{else if and $value.ReferenceTo $value.ReferenceTo.Description}}
     // Description: {{multiLineComment $value.ReferenceTo.Description}}
     {{end -}}
-    {{namify $key}} {{if and (not (isRequired $ $key)) (ne $value.Type "array")}}*{{end}}{{template "schema-name" $value}} `json:"{{convertKey $key}}"{{generateValidateTags $value.Validations}}`
+    {{namify $key}} {{if and (not (isRequired $ $key)) (ne $value.Type "array")}}*{{end}}{{template "schema-name" $value}} `{{generateJSONTags $value.Validations $key}}{{generateValidateTags $value.Validations}}`
     {{end -}}
 
     {{- if .AdditionalProperties}}