doc/hook: additional example for rejecting op (ent#2407)

doc/md/hooks.md

@@ -246,11 +246,25 @@ func (SomeMixin) Hooks() []ent.Hook {
     return []ent.Hook{
         // Execute "HookA" only for the UpdateOne and DeleteOne operations.
         hook.On(HookA(), ent.OpUpdateOne|ent.OpDeleteOne),
+
         // Don't execute "HookB" on Create operation.
         hook.Unless(HookB(), ent.OpCreate),
+
         // Execute "HookC" only if the ent.Mutation is changing the "status" field,
         // and clearing the "dirty" field.
         hook.If(HookC(), hook.And(hook.HasFields("status"), hook.HasClearedFields("dirty"))),
+
+        // Disallow changing the "password" field on Update (many) operation.
+        hook.If(
+            hook.FixedError(errors.New("password cannot be edited on update many")),
+            hook.And(
+                hook.HasOp(ent.OpUpdate),
+                hook.Or(
+                	hook.HasFields("password"),
+                	hook.HasClearedFields("password"),
+                ),
+            ),
+        ),
     }
 }
 ```

entc/integration/hooks/ent/schema/user.go

@@ -6,11 +6,13 @@ package schema
 
 import (
 	"context"
+	"errors"
 	"fmt"
 
-	"entgo.io/ent/entc/integration/hooks/ent/hook"
+	"entgo.io/ent/entc/integration/hooks/ent/user"
 
 	"entgo.io/ent"
+	"entgo.io/ent/entc/integration/hooks/ent/hook"
 	"entgo.io/ent/schema/edge"
 	"entgo.io/ent/schema/field"
 	"entgo.io/ent/schema/mixin"
@@ -34,6 +36,9 @@ func (User) Fields() []ent.Field {
 		field.String("name"),
 		field.Uint("worth").
 			Optional(),
+		field.String("password").
+			Optional().
+			Sensitive(),
 	}
 }
 
@@ -47,6 +52,22 @@ func (User) Edges() []ent.Edge {
 	}
 }
 
+// Hooks of the User.
+func (User) Hooks() []ent.Hook {
+	return []ent.Hook{
+		hook.If(
+			hook.FixedError(errors.New("password cannot be edited on update-many")),
+			hook.And(
+				hook.HasOp(ent.OpUpdate),
+				hook.Or(
+					hook.HasFields(user.FieldPassword),
+					hook.HasClearedFields(user.FieldPassword),
+				),
+			),
+		),
+	}
+}
+
 type VersionMixin struct {
 	mixin.Schema
 }