readme

README.md

@@ -836,19 +836,28 @@ The first argument to `:error/fn` is a map with keys:
 - `:schema`, the schema to explain
 - `:value` (optional), the value to explain
 - `:negated` (optional), a function returning the explanation of `(m/explain [:not schema] value)`.
-  If provided, then this call explains `(m/explain [:not schema] value)`.
-  Rarely needed but useful in some cases.
-  Note in this scenario, `(m/validate schema value)` is true and
-  the resulting error message will be negated by the `:error/fn` caller in the same way as `:error/message`
-  in service of a final explanation of `(m/explain [:not schema] value)`:
+  If provided, then we are explaining the failure of negating this schema via `(m/explain [:not schema] value)`.
+  Note in this scenario, `(m/validate schema value)` is true.
+  If returning a string, 
+  the resulting error message will be negated by the `:error/fn` caller in the same way as `:error/message`.
+  Returning `(negated string)` disables this behavior and `string` is used as the negated error message.
 ```clojure
-;; e.g.,
+;; automatic negation
 (me/humanize
   (m/explain
     [:not [:fn {:error/fn {:en (fn [_ _] "should not be a multiple of 3")}}
            #(not= 0 (mod % 3))]]
     1))
 ; => ["should be a multiple of 3"]
+
+;; manual negation
+(me/humanize
+  (m/explain [:not [:fn {:error/fn {:en (fn [{:keys [negated]} _]
+                                          (if negated
+                                            (negated "should not avoid being a multiple of 3")
+                                            "should not be a multiple of 3"))}}
+                    #(not= 0 (mod % 3))]] 1))
+; => ["should not avoid being a multiple of 3"]
 ```
 
 Here are some basic examples of `:error/message` and `:error/fn`: