Revert string control to class component

packages/netlify-cms-core/src/components/Editor/EditorControlPane/Widget.js

@@ -2,15 +2,10 @@ import PropTypes from 'prop-types';
 import React, { Component } from 'react';
 import ImmutablePropTypes from 'react-immutable-proptypes';
 import { Map, List } from 'immutable';
-import { oneLine } from 'common-tags';
 
 import { getRemarkPlugins } from '../../../lib/registry';
 import ValidationErrorTypes from '../../../constants/validationErrorTypes';
 
-function truthy() {
-  return { error: false };
-}
-
 function isEmpty(value) {
   return (
     value === null ||
@@ -23,7 +18,7 @@ function isEmpty(value) {
 
 export default class Widget extends Component {
   static propTypes = {
-    controlComponent: PropTypes.oneOfType([PropTypes.func, PropTypes.object]).isRequired,
+    controlComponent: PropTypes.func.isRequired,
     validator: PropTypes.func,
     field: ImmutablePropTypes.map.isRequired,
     hasActiveStyle: PropTypes.bool,
@@ -308,6 +303,7 @@ export default class Widget extends Component {
       onRemoveInsertedMedia,
       getAsset,
       forID: uniqueFieldId,
+      ref: this.processInnerControlRef,
       validate: this.validate,
       classNameWrapper,
       classNameWidget,

packages/netlify-cms-core/src/widgets/string/StringControl.tsx

@@ -1,52 +1,50 @@
-import React, { forwardRef, useCallback, useEffect, useState } from 'react';
-import { CmsWidgetControlProps } from '../../interface';
+import React from 'react';
 
-const StringControl = forwardRef<any, CmsWidgetControlProps<string>>(
-  ({
-    onChange,
-    forID,
-    value = '',
-    classNameWrapper,
-    setActiveStyle,
-    setInactiveStyle,
-  }: CmsWidgetControlProps<string>, _ref) => {
-    const [element, setElement] = useState<HTMLInputElement | null>(null);
-    const [selection, setSelection] = useState<number | null>(null);
+import type { ChangeEvent } from 'react';
+import type { CmsWidgetControlProps } from '../../interface';
 
-    const handleChange = useCallback((e: React.ChangeEvent<HTMLInputElement>) => {
-      setSelection(e.target.selectionStart);
-      onChange(e.target.value);
-    }, []);
+export default class StringControl extends React.Component<CmsWidgetControlProps<string>> {
+  // The selection to maintain for the input element
+  private _sel: number | null = 0;
 
-    const handleSetElement = useCallback((el: HTMLInputElement) => {
-      setElement(el);
-    }, []);
+  // The input element ref
+  private _el: HTMLInputElement | null = null;
 
-    useEffect(() => {
-      if (!element) {
-        return;
+  // NOTE: This prevents the cursor from jumping to the end of the text for
+  // nested inputs. In other words, this is not an issue on top-level text
+  // fields such as the `title` of a collection post. However, it becomes an
+  // issue on fields nested within other components, namely widgets nested
+  // within a `markdown` widget. For example, the alt text on a block image
+  // within markdown.
+  // SEE: https://github.com/netlify/netlify-cms/issues/4539
+  // SEE: https://github.com/netlify/netlify-cms/issues/3578
+  componentDidUpdate() {
+    if (this._el && this._el.selectionStart !== this._sel) {
+      this._el.setSelectionRange(this._sel, this._sel);
+    }
   }
 
-      if (element.selectionStart !== selection) {
-        element.setSelectionRange(selection, selection);
-      }
-    }, [element, element?.selectionStart, selection]);
+  handleChange = (e: ChangeEvent<HTMLInputElement>) => {
+    this._sel = e.target.selectionStart;
+    this.props.onChange(e.target.value);
+  };
+
+  render() {
+    const { forID, value, classNameWrapper, setActiveStyle, setInactiveStyle } = this.props;
 
     return (
       <input
-        ref={handleSetElement}
+        ref={el => {
+          this._el = el;
+        }}
         type="text"
         id={forID}
         className={classNameWrapper}
         value={value || ''}
-        onChange={handleChange}
+        onChange={this.handleChange}
         onFocus={setActiveStyle}
         onBlur={setInactiveStyle}
       />
     );
-  },
-);
-
-StringControl.displayName = 'StringControl';
-
-export default StringControl;
+  }
+}