allow for empty body in the exception (#690)

* allow for empty body in the exception

thrift doesn't allow for a void in the exception hence using annontation
to indicate that the exception doesn't have any body.

* add new line in some exception handling cases for proper formating

codegen/method.go

@@ -44,6 +44,7 @@ const (
 	// generated argument directly instead of a struct that warps the argument.
 	// The annotated method should have one and only one argument.
 	AntHTTPReqDefBoxed = "%s.http.req.def"
+	antHTTPResNoBody   = "%s.http.res.body.disallow"
 )
 
 const queryAnnotationPrefix = "query."
@@ -62,7 +63,8 @@ type PathSegment struct {
 type ExceptionSpec struct {
 	StructSpec
 
-	StatusCode StatusCode
+	StatusCode       StatusCode
+	IsBodyDisallowed bool
 }
 
 // HeaderFieldInfo contains information about where to store
@@ -162,6 +164,7 @@ type annotations struct {
 	Meta            string
 	Handler         string
 	HTTPReqDefBoxed string
+	HTTPResNoBody   string
 }
 
 // StructSpec specifies a Go struct to be generated.
@@ -207,6 +210,7 @@ func NewMethod(
 		Meta:            fmt.Sprintf(antMeta, ant),
 		Handler:         fmt.Sprintf(antHandler, ant),
 		HTTPReqDefBoxed: fmt.Sprintf(AntHTTPReqDefBoxed, ant),
+		HTTPResNoBody:   fmt.Sprintf(antHTTPResNoBody, ant),
 	}
 
 	method.GenCodePkgName, err = packageHelper.TypePackageName(thriftFile)
@@ -411,12 +415,14 @@ func (ms *MethodSpec) setExceptions(
 			)
 		}
 
+		bodyDisallowed := ms.isBodyDisallowed(e)
 		if !ms.WantAnnot {
 			exception := ExceptionSpec{
 				StructSpec: StructSpec{
 					Type: typeName,
 					Name: e.Name,
 				},
+				IsBodyDisallowed: bodyDisallowed,
 			}
 			ms.Exceptions[i] = exception
 			ms.ExceptionsIndex[e.Name] = exception
@@ -448,6 +454,7 @@ func (ms *MethodSpec) setExceptions(
 				Code:    code,
 				Message: e.Name,
 			},
+			IsBodyDisallowed: bodyDisallowed,
 		}
 		ms.Exceptions[i] = exception
 		ms.ExceptionsIndex[e.Name] = exception
@@ -1567,6 +1574,11 @@ func (ms *MethodSpec) isRequestBoxed(f *compile.FunctionSpec) bool {
 	return ok && boxed == "true"
 }
 
+func (ms *MethodSpec) isBodyDisallowed(f *compile.FieldSpec) bool {
+	val, ok := f.Annotations[ms.annotations.HTTPResNoBody]
+	return ok && val == "true"
+}
+
 func headers(annotation string) []string {
 	if annotation == "" {
 		return nil

codegen/templates/endpoint.tmpl

@@ -207,12 +207,26 @@ func (h *{{$handlerName}}) HandleRequest(
 		res.SendError(500, "Unexpected server error", err)
 		return
 		{{ else }}
+		{{$val := false}}
+		{{range $idx, $exception := .Exceptions}}
+			{{if not $exception.IsBodyDisallowed}}
+				{{$val = true}}
+			{{ end}}
+		{{end}}
+		{{ if $val -}}
 		switch errValue := err.(type) {
+		{{else -}}
+		switch err.(type) {
+		{{end -}}
 		{{range $idx, $exception := .Exceptions}}
 		case *{{$exception.Type}}:
+			{{if $exception.IsBodyDisallowed -}}
+			res.WriteJSONBytes({{$exception.StatusCode.Code}}, cliRespHeaders, nil)
+			{{else -}}
 			res.WriteJSON(
 				{{$exception.StatusCode.Code}}, cliRespHeaders, errValue,
 			)
+			{{end -}}
 			return
 		{{end}}
 		  default:

codegen/templates/http_client.tmpl

@@ -337,11 +337,14 @@ func (c *{{$clientName}}) {{$methodName}}(
 			return respHeaders, nil
 		{{range $code, $exceptions := .ExceptionsByStatusCode -}}
 		case {{$code}}:
-			{{- if or (eq $code 204) (eq $code 304) -}}
+			{{- if or (eq $code 204) (eq $code 304) }}
 				{{/* If multiple exceptions have 204/304 status code mapped, we aren't able to distinguish between them */}}
 				{{/* so we'll just return the first exception that has 204/304 status code set. */}}
 				{{$val := index $exceptions 0}}
 				return respHeaders, &{{$val.Type}}{}
+			{{ else if and (eq (len $exceptions) 1) (eq  (index $exceptions 0).IsBodyDisallowed true) -}}
+				{{$val := index $exceptions 0}}
+				return respHeaders, &{{$val.Type}}{}
 			{{else}}
 			allOptions := []interface{}{
 			{{range $idx, $exception := $exceptions -}}
@@ -364,7 +367,7 @@ func (c *{{$clientName}}) {{$methodName}}(
 	{{else}}
 	switch res.StatusCode {
 		case {{.OKStatusCode.Code}}:
-		{{- if or (eq (.OKStatusCode.Code) 204) (eq (.OKStatusCode.Code) 304) -}}
+		{{- if or (eq (.OKStatusCode.Code) 204) (eq (.OKStatusCode.Code) 304) }}
 			return {{if isPointerType .ResponseType}}&{{end}}{{unref .ResponseType}}{}, respHeaders, nil
 		{{- else }}
 		{{- if eq .ResponseType "[]byte"}}
@@ -389,11 +392,14 @@ func (c *{{$clientName}}) {{$methodName}}(
 		{{end}}
 		{{range $code, $exceptions := .ExceptionsByStatusCode -}}
 		case {{$code}}:
-			{{- if or (eq $code 204) (eq $code 304) -}}
+			{{- if or (eq $code 204) (eq $code 304) }}
 				{{/* If multiple exceptions have 204/304 status code mapped, we aren't able to distinguish between them */}}
 				{{/* so we'll just return the first exception that has 204/304 status code set. */}}
 				{{$val := index $exceptions 0}}
 				return defaultRes, respHeaders, &{{$val.Type}}{}
+			{{ else if and (eq (len $exceptions) 1) (eq  (index $exceptions 0).IsBodyDisallowed true) -}}
+				{{$val := index $exceptions 0}}
+				return defaultRes, respHeaders, &{{$val.Type}}{}
 			{{else}}
 			allOptions := []interface{}{
 				{{range $idx, $exception := $exceptions -}}