input restriction (Textualize#3657)

* input restriction

* types

* tweak

* tests

* docstring

* fix lock

* words

* add valid empty

* another test

* fix regex

* doc

* name change

* Fix regex

* force initial value

* force reactive

* test fix

* add plus

* input type literal

* export InputType

CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - CSS error reporting will no longer provide links to the files in question https://github.com/Textualize/textual/pull/3582
 - inline CSS error reporting will report widget/class variable where the CSS was read from https://github.com/Textualize/textual/pull/3582
+- Added `restrict`, `type`, `max_length`, and `valid_empty` to Input https://github.com/Textualize/textual/pull/3657
 
 ## [0.41.0] - 2023-10-31
 

docs/examples/widgets/input_types.py

@@ -0,0 +1,13 @@
+from textual.app import App, ComposeResult
+from textual.widgets import Input
+
+
+class InputApp(App):
+    def compose(self) -> ComposeResult:
+        yield Input(placeholder="An integer", type="integer")
+        yield Input(placeholder="A number", type="number")
+
+
+if __name__ == "__main__":
+    app = InputApp()
+    app.run()

docs/widgets/input.md

@@ -22,6 +22,47 @@ The example below shows how you might create a simple form using two `Input` wid
     --8<-- "docs/examples/widgets/input.py"
     ```
 
+
+### Input Types
+
+The `Input` widget supports a `type` parameter which will prevent the user from typing invalid characters.
+You can set `type` to any of the following values:
+
+
+| input.type  | Description                                 |
+| ----------- | ------------------------------------------- |
+| `"integer"` | Restricts input to integers.                |
+| `"number"`  | Restricts input to a floating point number. |
+| `"text"`    | Allow all text (no restrictions).           |
+
+=== "Output"
+
+    ```{.textual path="docs/examples/widgets/input_types.py" press="1234"}
+    ```
+
+=== "input_types.py"
+
+    ```python
+    --8<-- "docs/examples/widgets/input_types.py"
+    ```
+
+If you set `type` to something other than `"text"`, then the `Input` will apply the appropriate [validator](#validating-input).
+
+### Restricting Input
+
+You can limit input to particular characters by supplying the `restrict` parameter, which should be a regular expression.
+The `Input` widget will prevent the addition of any characters that would cause the regex to no longer match.
+For instance, if you wanted to limit characters to binary you could set `restrict=r"[01]*"`.
+
+!!! note
+
+    The `restrict` regular expression is applied to the full value and not just to the new character.
+
+### Maximum Length
+
+You can limit the length of the input by setting `max_length` to a value greater than zero.
+This will prevent the user from typing any more characters when the maximum has been reached.
+
 ### Validating Input
 
 You can supply one or more *[validators][textual.validation.Validator]* to the `Input` widget to validate the value.
@@ -71,15 +112,23 @@ Textual offers several [built-in validators][textual.validation] for common requ
 but you can easily roll your own by extending [Validator][textual.validation.Validator],
 as seen for `Palindrome` in the example above.
 
+#### Validate Empty
+
+If you set `valid_empty=True` then empty values will bypass any validators, and empty values will be considered valid.
+
 ## Reactive Attributes
 
-| Name              | Type   | Default | Description                                                     |
-|-------------------|--------|---------|-----------------------------------------------------------------|
-| `cursor_blink`    | `bool` | `True`  | True if cursor blinking is enabled.                             |
-| `value`           | `str`  | `""`    | The value currently in the text input.                          |
-| `cursor_position` | `int`  | `0`     | The index of the cursor in the value string.                    |
-| `placeholder`     | `str`  | `str`   | The dimmed placeholder text to display when the input is empty. |
-| `password`        | `bool` | `False` | True if the input should be masked.                             |
+| Name              | Type   | Default  | Description                                                     |
+| ----------------- | ------ | -------- | --------------------------------------------------------------- |
+| `cursor_blink`    | `bool` | `True`   | True if cursor blinking is enabled.                             |
+| `value`           | `str`  | `""`     | The value currently in the text input.                          |
+| `cursor_position` | `int`  | `0`      | The index of the cursor in the value string.                    |
+| `placeholder`     | `str`  | `""`     | The dimmed placeholder text to display when the input is empty. |
+| `password`        | `bool` | `False`  | True if the input should be masked.                             |
+| `restrict`        | `str`  | `None`   | Optional regular expression to restrict input.                  |
+| `type`            | `str`  | `"text"` | The type of the input.                                          |
+| `max_length`      | `int`  | `None`   | Maximum length of the input value.                              |
+| `valid_empty`     | `bool` | `False`  | Allow empty values to bypass validation.                        |
 
 ## Messages