openapi3: refacto error messages

Signed-off-by: Pierre Fenoll <pierrefenoll@gmail.com>

openapi3/loader.go

@@ -491,9 +491,22 @@ func (loader *Loader) resolveRef(doc *T, ref string, path *url.URL) (*T, string,
 	return doc, fragment, resolvedPath, nil
 }
 
+var (
+	errMUSTCallback       = errors.New("invalid callback: value MUST be an object")
+	errMUSTExample        = errors.New("invalid example: value MUST be an object")
+	errMUSTHeader         = errors.New("invalid header: value MUST be an object")
+	errMUSTLink           = errors.New("invalid link: value MUST be an object")
+	errMUSTParameter      = errors.New("invalid parameter: value MUST be an object")
+	errMUSTPathItem       = errors.New("invalid path item: value MUST be an object")
+	errMUSTRequestBody    = errors.New("invalid requestBody: value MUST be an object")
+	errMUSTResponse       = errors.New("invalid response: value MUST be an object")
+	errMUSTSchema         = errors.New("invalid schema: value MUST be an object")
+	errMUSTSecurityScheme = errors.New("invalid securityScheme: value MUST be an object")
+)
+
 func (loader *Loader) resolveHeaderRef(doc *T, component *HeaderRef, documentPath *url.URL) (err error) {
 	if component.isEmpty() {
-		return errors.New("invalid header: value MUST be an object")
+		return errMUSTHeader
 	}
 
 	if component.Value != nil {
@@ -540,7 +553,7 @@ func (loader *Loader) resolveHeaderRef(doc *T, component *HeaderRef, documentPat
 
 func (loader *Loader) resolveParameterRef(doc *T, component *ParameterRef, documentPath *url.URL) (err error) {
 	if component.isEmpty() {
-		return errors.New("invalid parameter: value MUST be an object")
+		return errMUSTParameter
 	}
 
 	if component.Value != nil {
@@ -597,7 +610,7 @@ func (loader *Loader) resolveParameterRef(doc *T, component *ParameterRef, docum
 
 func (loader *Loader) resolveRequestBodyRef(doc *T, component *RequestBodyRef, documentPath *url.URL) (err error) {
 	if component.isEmpty() {
-		return errors.New("invalid requestBody: value MUST be an object")
+		return errMUSTRequestBody
 	}
 
 	if component.Value != nil {
@@ -661,7 +674,7 @@ func (loader *Loader) resolveRequestBodyRef(doc *T, component *RequestBodyRef, d
 
 func (loader *Loader) resolveResponseRef(doc *T, component *ResponseRef, documentPath *url.URL) (err error) {
 	if component.isEmpty() {
-		return errors.New("invalid response: value MUST be an object")
+		return errMUSTResponse
 	}
 
 	if component.Value != nil {
@@ -736,7 +749,7 @@ func (loader *Loader) resolveResponseRef(doc *T, component *ResponseRef, documen
 
 func (loader *Loader) resolveSchemaRef(doc *T, component *SchemaRef, documentPath *url.URL, visited []string) (err error) {
 	if component.isEmpty() {
-		return errors.New("invalid schema: value MUST be an object")
+		return errMUSTSchema
 	}
 
 	if component.Value != nil {
@@ -824,7 +837,7 @@ func (loader *Loader) resolveSchemaRef(doc *T, component *SchemaRef, documentPat
 
 func (loader *Loader) resolveSecuritySchemeRef(doc *T, component *SecuritySchemeRef, documentPath *url.URL) (err error) {
 	if component.isEmpty() {
-		return errors.New("invalid securityScheme: value MUST be an object")
+		return errMUSTSecurityScheme
 	}
 
 	if component.Value != nil {
@@ -861,7 +874,7 @@ func (loader *Loader) resolveSecuritySchemeRef(doc *T, component *SecurityScheme
 
 func (loader *Loader) resolveExampleRef(doc *T, component *ExampleRef, documentPath *url.URL) (err error) {
 	if component.isEmpty() {
-		return errors.New("invalid example: value MUST be an object")
+		return errMUSTExample
 	}
 
 	if component.Value != nil {
@@ -898,7 +911,7 @@ func (loader *Loader) resolveExampleRef(doc *T, component *ExampleRef, documentP
 
 func (loader *Loader) resolveCallbackRef(doc *T, component *CallbackRef, documentPath *url.URL) (err error) {
 	if component.isEmpty() {
-		return errors.New("invalid callback: value MUST be an object")
+		return errMUSTCallback
 	}
 
 	if component.Value != nil {
@@ -945,7 +958,7 @@ func (loader *Loader) resolveCallbackRef(doc *T, component *CallbackRef, documen
 
 func (loader *Loader) resolveLinkRef(doc *T, component *LinkRef, documentPath *url.URL) (err error) {
 	if component.isEmpty() {
-		return errors.New("invalid link: value MUST be an object")
+		return errMUSTLink
 	}
 
 	if component.Value != nil {
@@ -982,7 +995,7 @@ func (loader *Loader) resolveLinkRef(doc *T, component *LinkRef, documentPath *u
 
 func (loader *Loader) resolvePathItemRef(doc *T, pathItem *PathItem, documentPath *url.URL) (err error) {
 	if pathItem == nil {
-		err = errors.New("invalid path item: value MUST be an object")
+		err = errMUSTPathItem
 		return
 	}