✨ Add JSON marshalling

interface.go

@@ -1,5 +1,7 @@
 package errors
 
+import "encoding/json"
+
 // ResponsableError is an error that has information useful in an HTTP response.
 // The string returned by Error should be suitable for logging useful information
 // to assist debugging the error.
@@ -8,10 +10,16 @@ package errors
 //
 // Msg should return a message suitable to display to the end user. If the message
 // returned by Error is safe for the end user, it may simply call that.
+//
+// JSON should return something that can be marshalled to JSON for the response body.
+// It can be something as simple as map[string]string{"error":err.Msg()}.
+// JSON's return value should be used by MarshalJSON()
 type ResponsableError interface {
+	json.Marshaler
 	Error() string
 	Status() int
 	Msg() string
+	JSON() any
 }
 
 // SettableError is a ResponsableError which can be modified after initial creation.
@@ -22,10 +30,13 @@ type ResponsableError interface {
 // Methods are chainable.
 //
 // SetStatus should not use a value outside of 100-599. It may either ignore such values, or panic.
+//
+// SetField should add some metadata to the error, which will be included in the data returned by JSON()
 type SettableError interface {
 	ResponsableError
 	SetStatus(int) SettableError
 	SetMsg(string, ...any) SettableError
+	SetField(string, any) SettableError
 }
 
 // UnwrappableError allows a ResponsableError to wrap another error.