From 3bc4aa19bb74cacef27c827df626a2451ba3de99 Mon Sep 17 00:00:00 2001
From: Rodgers <cptrodgers@gmail.com>
Date: Sat, 11 Sep 2021 23:31:43 +0700
Subject: [PATCH] Add document for Input Validator with Extensions

---
 docs/en/src/input_value_validators.md | 32 +++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/docs/en/src/input_value_validators.md b/docs/en/src/input_value_validators.md
index 49ae65d4..46bfb9eb 100644
--- a/docs/en/src/input_value_validators.md
+++ b/docs/en/src/input_value_validators.md
@@ -85,3 +85,35 @@ impl InputValueValidator for MustBeZero {
     }
 }
 ```
+
+Here is an example of a custom validator with extensions (return `async_graphql::Error`):
+
+```rust
+pub struct Email;
+
+impl InputValueValidator for Email {
+    fn is_valid_with_extensions(&self, value: &Value) -> Result<(), Error> {
+        if let Value::String(s) = value {
+            if &s.to_lowercase() != s {
+                return Err(Error::new("Validation Error").extend_with(|_, e| {
+                    e.set("key", "email_must_lowercase")
+                }));
+            }
+
+            if !validate_non_control_character(s) {
+                return Err(Error::new("Validation Error").extend_with(|_, e| {
+                    e.set("key", "email_must_no_non_control_character")
+                }));
+            }
+
+            if !validate_email(s) {
+                return Err(Error::new("Validation Error").extend_with(|_, e| {
+                    e.set("key", "invalid_email_format")
+                }));
+            }
+        }
+
+        Ok(())
+    }
+}
+```