Added link to warning example

Author: erikras

README.md

@@ -120,6 +120,7 @@ const MyForm = () => (
   * [Loading and Initializing Values](#loading-and-initializing-values)
   * [Field Arrays](#field-arrays)
   * [Calculated Fields](#calculated-fields)
+  * [Field Warnings](#field-warnings)
 * [Rendering](#rendering)
 * [API](#api)
   * [`Field : React.ComponentType<FieldProps>`](#field--reactcomponenttypefieldprops)
@@ -258,6 +259,12 @@ Demonstrates how to use the
 [`final-form-calculate`](https://github.com/final-form/final-form-calculate)
 decorator to achieve realtime field calculations through easily defined rules.
 
+### [Field Warnings](https://codesandbox.io/s/m5qwxpr6o8)
+
+Demonstrates how the power of subscriptions and mutators can be used to build a
+warning engine: logic to display a message next to each field that is _not_ an
+error that prevents form submission.
+
 ## Rendering
 
 There are three ways to tell `<Form/>` and `<Field/>` what to render:

docs/comparison.md

@@ -6,12 +6,14 @@ and you'd like it to be), please correct the mistake.
 
 | Feature                               |              [🏁 React-Final-Form](https://github.com/final-form/react-final-form#-react-final-form)              | [Formik](https://github.com/jaredpalmer/formik)  |  [Redux-Form](https://github.com/erikras/redux-form)  |
 | ------------------------------------- | :---------------------------------------------------------------------------------------------------------------: | :----------------------------------------------: | :---------------------------------------------------: |
-| Bundle Size                           | [3.5k](https://bundlephobia.com/result?p=final-form) + [2.5k](https://bundlephobia.com/result?p=react-final-form) | [7.5k](https://bundlephobia.com/result?p=formik) | [26.8k](https://bundlephobia.com/result?p=redux-form) |
+| Bundle Size                           | [3.5k](https://bundlephobia.com/result?p=final-form) + [2.6k](https://bundlephobia.com/result?p=react-final-form) | [7.1k](https://bundlephobia.com/result?p=formik) | [26.8k](https://bundlephobia.com/result?p=redux-form) |
 | Works without Redux                   |                                                        ✅                                                         |                        ✅                        |                          ❌                           |
 | Record-Level Sync Validation          |                                                        ✅                                                         |                        ✅                        |                          ✅                           |
 | Record-Level Async Validation         |                                                        ✅                                                         |                        ✅                        |                          ✅                           |
 | Field-Level Sync Validation           |                                                        ✅                                                         |                        ✅                        |                          ✅                           |
 | Field Level Async Validation          |                                                        ✅                                                         |                        ✅                        |                          ✅                           |
+| Field Warnings                        |                                                        ✅                                                         |                        ❌                        |                          ✅                           |
+| Calculated Fields                     |                                                        ✅                                                         |                        ❌                        |                          ✅                           |
 | Render Prop for Form                  |                                                        ✅                                                         |                        ✅                        |                          ❌                           |
 | Render Prop for Field                 |                                                        ✅                                                         |                        ✅                        |                          ❌                           |
 | Array Fields                          |                                              ✅ <sup>[1](#footnote1)                                              |                        ❌                        |                          ✅                           |