Type aliasing (deepmap#232)

* Add aliasable types logic and option

* Update templates

* Re-generate examples

cmd/oapi-codegen/oapi-codegen.go

@@ -43,6 +43,7 @@ var (
 	flagImportMapping  string
 	flagExcludeSchemas string
 	flagConfigFile     string
+	flagAliasTypes     bool
 )
 
 type configuration struct {
@@ -68,6 +69,7 @@ func main() {
 	flag.StringVar(&flagImportMapping, "import-mapping", "", "A dict from the external reference to golang package path")
 	flag.StringVar(&flagExcludeSchemas, "exclude-schemas", "", "A comma separated list of schemas which must be excluded from generation")
 	flag.StringVar(&flagConfigFile, "config", "", "a YAML config file that controls oapi-codegen behavior")
+	flag.BoolVar(&flagAliasTypes, "alias-types", false, "Alias type declarations of possible")
 	flag.Parse()
 
 	if flag.NArg() < 1 {
@@ -87,7 +89,9 @@ func main() {
 		cfg.PackageName = codegen.ToCamelCase(nameParts[0])
 	}
 
-	opts := codegen.Options{}
+	opts := codegen.Options{
+		AliasTypes: flagAliasTypes,
+	}
 	for _, g := range cfg.GenerateTargets {
 		switch g {
 		case "client":

pkg/codegen/codegen.go

@@ -38,6 +38,7 @@ type Options struct {
 	EmbedSpec          bool              // Whether to embed the swagger spec in the generated code
 	SkipFmt            bool              // Whether to skip go imports on the generated code
 	SkipPrune          bool              // Whether to skip pruning unused components on the generated code
+	AliasTypes         bool              // Whether to alias types if possible
 	IncludeTags        []string          // Only include operations that have one of these tags. Ignored when empty.
 	ExcludeTags        []string          // Exclude operations that have one of these tags. Ignored when empty.
 	UserTemplates      map[string]string // Override built-in templates from user-provided files
@@ -110,6 +111,7 @@ func Generate(swagger *openapi3.Swagger, packageName string, opts Options) (stri
 	}
 
 	// This creates the golang templates text package
+	TemplateFunctions["opts"] = func() Options { return opts }
 	t := template.New("oapi-codegen").Funcs(TemplateFunctions)
 	// This parses all of our own template files into the template object
 	// above

pkg/codegen/operations.go

@@ -333,8 +333,11 @@ type RequestBodyDefinition struct {
 }
 
 // Returns the Go type definition for a request body
-func (r RequestBodyDefinition) TypeDef() string {
-	return r.Schema.TypeDecl()
+func (r RequestBodyDefinition) TypeDef(opID string) *TypeDefinition {
+	return &TypeDefinition{
+		TypeName: fmt.Sprintf("%s%sRequestBody", opID, r.NameTag),
+		Schema:   r.Schema,
+	}
 }
 
 // Returns whether the body is a custom inline type, or pre-defined. This is

pkg/codegen/schema.go

@@ -13,6 +13,8 @@ type Schema struct {
 	GoType  string // The Go type needed to represent the schema
 	RefType string // If the type has a type name, this is set
 
+	ArrayType *Schema // The schema of array element
+
 	EnumValues map[string]string // Enum values
 
 	Properties               []Property       // For an object, the fields with names
@@ -81,6 +83,11 @@ type TypeDefinition struct {
 	Schema       Schema
 }
 
+func (t *TypeDefinition) CanAlias() bool {
+	return t.Schema.IsRef() || /* actual reference */
+		(t.Schema.ArrayType != nil && t.Schema.ArrayType.IsRef()) /* array to ref */
+}
+
 func PropertiesEqual(a, b Property) bool {
 	return a.JsonFieldName == b.JsonFieldName && a.Schema.TypeDecl() == b.Schema.TypeDecl() && a.Required == b.Required
 }
@@ -235,6 +242,7 @@ func GenerateGoSchema(sref *openapi3.SchemaRef, path []string) (Schema, error) {
 			if err != nil {
 				return Schema{}, errors.Wrap(err, "error generating type for array")
 			}
+			outSchema.ArrayType = &arrayType
 			outSchema.GoType = "[]" + arrayType.TypeDecl()
 			outSchema.Properties = arrayType.Properties
 		case "integer":

pkg/codegen/templates/param-types.tmpl

@@ -1,6 +1,6 @@
 {{range .}}{{$opid := .OperationId}}
 {{range .TypeDefinitions}}
 // {{.TypeName}} defines parameters for {{$opid}}.
-type {{.TypeName}} {{.Schema.TypeDecl}}
+type {{.TypeName}} {{if and (opts.AliasTypes) (.CanAlias)}}={{end}} {{.Schema.TypeDecl}}
 {{end}}
 {{end}}

pkg/codegen/templates/request-bodies.tmpl

@@ -1,6 +1,8 @@
 {{range .}}{{$opid := .OperationId}}
 {{range .Bodies}}
-// {{$opid}}RequestBody defines body for {{$opid}} for application/json ContentType.
-type {{$opid}}{{.NameTag}}RequestBody {{.TypeDef}}
+{{with .TypeDef $opid}}
+// {{.TypeName}} defines body for {{$opid}} for application/json ContentType.
+type {{.TypeName}} {{if and (opts.AliasTypes) (.CanAlias)}}={{end}} {{.Schema.TypeDecl}}
+{{end}}
 {{end}}
 {{end}}

pkg/codegen/templates/typedef.tmpl

@@ -1,6 +1,6 @@
 {{range .Types}}
 // {{.TypeName}} defines model for {{.JsonName}}.
-type {{.TypeName}} {{.Schema.TypeDecl}}
+type {{.TypeName}} {{if and (opts.AliasTypes) (.CanAlias)}}={{end}} {{.Schema.TypeDecl}}
 {{- if gt (len .Schema.EnumValues) 0 }}
 // List of {{ .TypeName }}
 const (