Add WithBuilder and FromContext (#38)

context.go

@@ -0,0 +1,17 @@
+package oops
+
+import "context"
+
+type contextKey string
+
+const contextKeyOops = contextKey("oops")
+
+func getBuilderFromContext(ctx context.Context) (OopsErrorBuilder, bool) {
+	b, ok := ctx.Value(contextKeyOops).(OopsErrorBuilder)
+	return b, ok
+}
+
+// WithBuilder set the error builder in the context, to be retrieved later with FromContext.
+func WithBuilder(ctx context.Context, builder OopsErrorBuilder) context.Context {
+	return context.WithValue(ctx, contextKeyOops, builder)
+}

oops.go

@@ -30,6 +30,15 @@ func Errorf(format string, args ...any) error {
 	return new().Errorf(format, args...)
 }
 
+func FromContext(ctx context.Context) OopsErrorBuilder {
+	builder, ok := getBuilderFromContext(ctx)
+	if !ok {
+		new()
+	}
+
+	return builder
+}
+
 func Join(e ...error) error {
 	return new().Join(e...)
 }

oops_test.go

@@ -41,6 +41,20 @@ func TestOopsWrapf(t *testing.T) {
 	is.Nil(err)
 }
 
+func TestOopsFromContext(t *testing.T) {
+	is := assert.New(t)
+
+	domain := "domain"
+	key, val := "foo", "bar"
+	builder := new().In(domain).With(key, val).WithContext(context.Background())
+	ctx := WithBuilder(context.Background(), builder)
+
+	err := FromContext(ctx).Errorf("a message %d", 42)
+	is.Error(err)
+	is.Equal(domain, err.(OopsError).domain)
+	is.Equal(val, err.(OopsError).context[key])
+}
+
 func TestOopsErrorf(t *testing.T) {
 	is := assert.New(t)