Add allowEmptyValue overwrite

dsl/validation.go

@@ -381,6 +381,17 @@ func MinLength(val int) {
 	}
 }
 
+// AllowEmptyValue sets the AllowEmptyValue flag for a query or header parameter.
+// If not set, default behavior in paramFor is in != "path".
+func AllowEmptyValue(val bool) {
+	if a, ok := eval.Current().(*expr.AttributeExpr); ok {
+		if a.Validation == nil {
+			a.Validation = &expr.ValidationExpr{}
+		}
+		a.Validation.AllowEmptyValue = &val
+	}
+}
+
 // MaxLength adds a "maxItems" validation to the attribute.
 // See http://json-schema.org/latest/json-schema-validation.html#anchor42.
 //

expr/attribute.go

@@ -98,6 +98,9 @@ type (
 		// described at
 		// http://json-schema.org/latest/json-schema-validation.html#anchor61.
 		Required []string
+		// AllowEmptyValue indicates whether the attribute allows empty
+		// values. This is primarily used for query string parameters.
+		AllowEmptyValue *bool
 	}
 
 	// ValidationFormat is the type used to enumerate the possible string

http/codegen/openapi/v3/parameters.go

@@ -55,11 +55,16 @@ func paramsFromHeadersAndCookies(endpoint *expr.HTTPEndpointExpr, rand *expr.Exa
 
 // paramFor converts the given attribute into a OpenAPI spec parameter.
 func paramFor(att *expr.AttributeExpr, name, in string, required bool, rand *expr.ExampleGenerator) *Parameter {
+	allowEmpty := in != "path"
+	if att.Validation != nil && att.Validation.AllowEmptyValue != nil {
+		allowEmpty = *att.Validation.AllowEmptyValue
+	}
+
 	param := &Parameter{
 		Name:            name,
 		In:              in,
 		Description:     att.Description,
-		AllowEmptyValue: in != "path",
+		AllowEmptyValue: allowEmpty,
 		Required:        required,
 		Schema:          newSchemafier(rand).schemafy(att),
 		Extensions:      openapi.ExtensionsFromExpr(att.Meta),