fixed issue 1715

Author: t1babin

examples/test1715.py

@@ -0,0 +1,16 @@
+from prompt_toolkit.shortcuts import input_dialog
+from prompt_toolkit.validation import Validator
+
+
+def is_number(text):
+    return text.isdigit()
+
+
+validator = Validator.from_callable(
+    is_number,
+    error_message='This input contains non-numeric characters')
+
+age = input_dialog(title="Age", text="Your age:",
+                   validator=validator).run()
+
+print(f"Your age: {age}")

src/prompt_toolkit/shortcuts/dialogs.py

@@ -18,7 +18,7 @@
 from prompt_toolkit.layout.containers import AnyContainer, HSplit
 from prompt_toolkit.layout.dimension import Dimension as D
 from prompt_toolkit.styles import BaseStyle
-from prompt_toolkit.validation import Validator
+from prompt_toolkit.validation import Validator, ValidationError
 from prompt_toolkit.widgets import (
     Box,
     Button,
@@ -124,7 +124,14 @@ def accept(buf: Buffer) -> bool:
         return True  # Keep text.
 
     def ok_handler() -> None:
-        get_app().exit(result=textfield.text)
+        if validator is None:
+            get_app().exit(result=textfield.text)
+        else:
+            try:
+                textfield.validator.validate(textfield.document)
+                get_app().exit(result=textfield.text)
+            except ValidationError:
+                get_app().layout.focus(textfield)
 
     ok_button = Button(text=ok_text, handler=ok_handler)
     cancel_button = Button(text=cancel_text, handler=_return_none)