Markdown editor: Remove character limit

## Issue
Closes 5687: Ensure post mode has no text limit

## Changes
- `type="markdown"` can now have unlimited length if clients don't define `textAreaMaxWidth`.
- The internal default limit of 2000 is narrowed down to `type=textarea`.

ui/component/common/form-components/form-field.jsx

@@ -80,7 +80,7 @@ export class FormField extends React.PureComponent<Props> {
       labelOnLeft,
       blockWrap,
       charCount,
-      textAreaMaxLength = FF_MAX_CHARS_DEFAULT,
+      textAreaMaxLength,
       quickActionLabel,
       quickActionHandler,
       ...inputProps
@@ -208,7 +208,7 @@ export class FormField extends React.PureComponent<Props> {
         // to pass the current value to it's callback, nor query the current
         // text length from the callback. So, we'll use our own widget.
         const hasCharCount = charCount !== undefined && charCount >= 0;
-        const countInfo = hasCharCount && (
+        const countInfo = hasCharCount && textAreaMaxLength !== undefined && (
           <span className="comment__char-count-mde">{`${charCount || '0'}/${textAreaMaxLength}`}</span>
         );
 
@@ -242,7 +242,7 @@ export class FormField extends React.PureComponent<Props> {
         );
       } else if (type === 'textarea') {
         const hasCharCount = charCount !== undefined && charCount >= 0;
-        const countInfo = hasCharCount && (
+        const countInfo = hasCharCount && textAreaMaxLength !== undefined && (
           <span className="comment__char-count">{`${charCount || '0'}/${textAreaMaxLength}`}</span>
         );
         input = (
@@ -255,7 +255,13 @@ export class FormField extends React.PureComponent<Props> {
                 {quickAction}
               </div>
             )}
-            <textarea type={type} id={name} maxLength={textAreaMaxLength} ref={this.input} {...inputProps} />
+            <textarea
+              type={type}
+              id={name}
+              maxLength={textAreaMaxLength || FF_MAX_CHARS_DEFAULT}
+              ref={this.input}
+              {...inputProps}
+            />
             {countInfo}
           </fieldset-section>
         );

ui/component/postEditor/view.jsx

@@ -1,6 +1,5 @@
 // @flow
 import React, { useEffect } from 'react';
-import { FF_MAX_CHARS_IN_POST } from 'constants/form-field';
 import { FormField } from 'component/common/form';
 
 type Props = {
@@ -12,10 +11,10 @@ type Props = {
   fileMimeType: ?string,
   streamingUrl: ?string,
   isStillEditing: boolean,
-  fetchStreamingUrl: string => void,
-  setPrevFileText: string => void,
+  fetchStreamingUrl: (string) => void,
+  setPrevFileText: (string) => void,
   updatePublishForm: ({}) => void,
-  setCurrentFileType: string => void,
+  setCurrentFileType: (string) => void,
 };
 
 function PostEditor(props: Props) {
@@ -62,7 +61,7 @@ function PostEditor(props: Props) {
 
   useEffect(() => {
     function readFileStream(url) {
-      return fetch(url).then(res => res.text());
+      return fetch(url).then((res) => res.text());
     }
 
     async function updateEditorText(url) {
@@ -107,8 +106,7 @@ function PostEditor(props: Props) {
       placeholder={__('My content for this post...')}
       value={ready ? fileText : __('Loading...')}
       disabled={!ready || disabled}
-      onChange={value => updatePublishForm({ fileText: value })}
-      textAreaMaxLength={FF_MAX_CHARS_IN_POST}
+      onChange={(value) => updatePublishForm({ fileText: value })}
     />
   );
 }

ui/constants/form-field.js

@@ -1,4 +1,3 @@
 export const FF_MAX_CHARS_DEFAULT = 2000;
 export const FF_MAX_CHARS_IN_COMMENT = 2000;
 export const FF_MAX_CHARS_IN_DESCRIPTION = 5000;
-export const FF_MAX_CHARS_IN_POST = 10000;