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package errorx
import (
"context"
)
// Property is a key to a dynamic property of an error.
// Property value belongs to an error instance only, never inherited from a type.
// Property visibility is hindered by Wrap, preserved by Decorate.
type Property struct {
*property // Property is compared by this pointer.
}
type property struct {
label string
printable bool
}
// RegisterProperty registers a new property key.
// It is used both to add a dynamic property to an error instance, and to extract property value back from error.
func RegisterProperty(label string) Property {
return newProperty(label, false)
}
// RegisterPrintableProperty registers a new property key for informational value.
// It is used both to add a dynamic property to an error instance, and to extract property value back from error.
// Printable property will be included in Error() message, both name and value.
func RegisterPrintableProperty(label string) Property {
return newProperty(label, true)
}
// PropertyContext is a context property, value is expected to be of context.Context type.
func PropertyContext() Property {
return propertyContext
}
// PropertyPayload is a payload property, value may contain user defined structure with arbitrary data passed along with an error.
func PropertyPayload() Property {
return propertyPayload
}
// WithContext is a statically typed helper to add a context property to an error.
func WithContext(err *Error, ctx context.Context) *Error {
return err.WithProperty(PropertyContext(), ctx)
}
// ExtractContext is a statically typed helper to extract a context property from an error.
func ExtractContext(err error) (context.Context, bool) {
rawCtx, ok := ExtractProperty(err, PropertyContext())
if !ok {
return nil, false
}
return rawCtx.(context.Context), true
}
// WithPayload is a helper to add a payload property to an error.
func WithPayload(err *Error, payload interface{}) *Error {
return err.WithProperty(PropertyPayload(), payload)
}
// ExtractPayload is a helper to extract a payload property from an error.
func ExtractPayload(err error) (interface{}, bool) {
return ExtractProperty(err, PropertyPayload())
}
// ExtractProperty attempts to extract a property value by a provided key.
// A property may belong to this error or be extracted from the original cause.
func ExtractProperty(err error, key Property) (interface{}, bool) {
typedErr := Cast(err)
if typedErr == nil {
return nil, false
}
return typedErr.Property(key)
}
var (
propertyContext = RegisterProperty("ctx")
propertyPayload = RegisterProperty("payload")
propertyUnderlying = RegisterProperty("underlying")
)
func newProperty(label string, printable bool) Property {
p := Property{
&property{
label: label,
printable: printable,
},
}
return p
}
// propertyMap represents map of properties.
// Compared to builtin type, it uses less allocations and reallocations on copy.
// It is implemented as a simple linked list.
type propertyMap struct {
p Property
value interface{}
next *propertyMap
}
func (pm *propertyMap) with(p Property, value interface{}) *propertyMap {
return &propertyMap{p: p, value: value, next: pm}
}
func (pm *propertyMap) get(p Property) (value interface{}, ok bool) {
for pm != nil {
if pm.p == p {
return pm.value, true
}
pm = pm.next
}
return nil, false
}
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