fix textarea maxlength issue (#33910)

* fix: textarea maxlength

* refactor: delete some useless code

* refactor: fix ci

* refactor and fix test case fall

* update snapshot

* add testcase

* refactor type defined

components/input/TextArea.tsx

@@ -17,6 +17,26 @@ function fixEmojiLength(value: string, maxLength: number) {
   return [...(value || '')].slice(0, maxLength).join('');
 }
 
+function setTriggerValue(
+  isCursorInEnd: boolean,
+  preValue: string,
+  triggerValue: string,
+  maxLength: number,
+) {
+  let newTriggerValue = triggerValue;
+  if (isCursorInEnd) {
+    // 光标在尾部，直接截断
+    newTriggerValue = fixEmojiLength(triggerValue, maxLength!);
+  } else if (
+    [...(preValue || '')].length < triggerValue.length &&
+    [...(triggerValue || '')].length > maxLength!
+  ) {
+    // 光标在中间，如果最后的值超过最大值，则采用原先的值
+    newTriggerValue = preValue;
+  }
+  return newTriggerValue;
+}
+
 export interface TextAreaProps extends RcTextAreaProps {
   allowClear?: boolean;
   bordered?: boolean;
@@ -54,6 +74,8 @@ const TextArea = React.forwardRef<TextAreaRef, TextAreaProps>(
     const clearableInputRef = React.useRef<ClearableLabeledInput>(null);
 
     const [compositing, setCompositing] = React.useState(false);
+    const oldCompositionValueRef = React.useRef<string>();
+    const oldSelectionStartRef = React.useRef<number>(0);
 
     const [value, setValue] = useMergedState(props.defaultValue, {
       value: props.value,
@@ -73,6 +95,10 @@ const TextArea = React.forwardRef<TextAreaRef, TextAreaProps>(
 
     const onInternalCompositionStart: React.CompositionEventHandler<HTMLTextAreaElement> = e => {
       setCompositing(true);
+      // 拼音输入前保存一份旧值
+      oldCompositionValueRef.current = value as string;
+      // 保存旧的光标位置
+      oldSelectionStartRef.current = e.currentTarget.selectionStart;
       onCompositionStart?.(e);
     };
 
@@ -81,9 +107,16 @@ const TextArea = React.forwardRef<TextAreaRef, TextAreaProps>(
 
       let triggerValue = e.currentTarget.value;
       if (hasMaxLength) {
-        triggerValue = fixEmojiLength(triggerValue, maxLength!);
+        const isCursorInEnd =
+          oldSelectionStartRef.current >= maxLength! + 1 ||
+          oldSelectionStartRef.current === oldCompositionValueRef.current?.length;
+        triggerValue = setTriggerValue(
+          isCursorInEnd,
+          oldCompositionValueRef.current as string,
+          triggerValue,
+          maxLength!,
+        );
       }
-
       // Patch composition onChange when value changed
       if (triggerValue !== value) {
         handleSetValue(triggerValue);
@@ -96,9 +129,13 @@ const TextArea = React.forwardRef<TextAreaRef, TextAreaProps>(
     const handleChange = (e: React.ChangeEvent<HTMLTextAreaElement>) => {
       let triggerValue = e.target.value;
       if (!compositing && hasMaxLength) {
-        triggerValue = fixEmojiLength(triggerValue, maxLength!);
+        // 1. 复制粘贴超过maxlength的情况 2.未超过maxlength的情况
+        const isCursorInEnd =
+          e.target.selectionStart >= maxLength! + 1 ||
+          e.target.selectionStart === triggerValue.length ||
+          !e.target.selectionStart;
+        triggerValue = setTriggerValue(isCursorInEnd, value as string, triggerValue, maxLength!);
       }
-
       handleSetValue(triggerValue);
       resolveOnChange(e.currentTarget, e, onChange, triggerValue);
     };

components/input/__tests__/__snapshots__/demo-extend.test.ts.snap

@@ -9530,10 +9530,19 @@ Array [
 `;
 
 exports[`renders ./components/input/demo/textarea.md extend context correctly 1`] = `
-<textarea
-  class="ant-input"
-  rows="4"
-/>
+Array [
+  <textarea
+    class="ant-input"
+    rows="4"
+  />,
+  <br />,
+  <br />,
+  <textarea
+    class="ant-input"
+    placeholder="maxLength is 6"
+    rows="4"
+  />,
+]
 `;
 
 exports[`renders ./components/input/demo/textarea-resize.md extend context correctly 1`] = `

components/input/__tests__/__snapshots__/demo.test.js.snap

@@ -3304,10 +3304,19 @@ Array [
 `;
 
 exports[`renders ./components/input/demo/textarea.md correctly 1`] = `
-<textarea
-  class="ant-input"
-  rows="4"
-/>
+Array [
+  <textarea
+    class="ant-input"
+    rows="4"
+  />,
+  <br />,
+  <br />,
+  <textarea
+    class="ant-input"
+    placeholder="maxLength is 6"
+    rows="4"
+  />,
+]
 `;
 
 exports[`renders ./components/input/demo/textarea-resize.md correctly 1`] = `

components/input/__tests__/textarea.test.js

@@ -110,6 +110,64 @@ describe('TextArea', () => {
         expect.objectContaining({ target: expect.objectContaining({ value: '竹' }) }),
       );
     });
+
+    // 字符输入
+    it('should not cut off string when cursor position is not at the end', () => {
+      const onChange = jest.fn();
+      const wrapper = mount(<TextArea maxLength={6} defaultValue="123456" onChange={onChange} />);
+      wrapper
+        .find('textarea')
+        .simulate('change', { target: { selectionStart: 1, value: 'w123456' } });
+      wrapper
+        .find('textarea')
+        .simulate('change', { target: { selectionStart: 3, value: '123w456' } });
+      expect(wrapper.find('textarea').at(0).getDOMNode().value).toBe('123456');
+    });
+
+    // 拼音输入
+    // 1. 光标位于最后，且当前字符数未达到6个，若选中的字符 + 原字符的长度超过6个，则将最终的字符按照maxlength截断
+    it('when the input method is pinyin and the cursor is at the end, should use maxLength to crop', () => {
+      const onChange = jest.fn();
+      const wrapper = mount(<TextArea maxLength={6} defaultValue="1234" onChange={onChange} />);
+      wrapper.find('textarea').instance().value = '1234'; // enzyme not support change `currentTarget`
+      wrapper.find('textarea').instance().selectionStart = 4;
+      wrapper.find('textarea').simulate('compositionStart');
+
+      wrapper
+        .find('textarea')
+        .simulate('change', { target: { selectionStart: 9, value: '1234z z z' } });
+      wrapper
+        .find('textarea')
+        .simulate('change', { target: { selectionStart: 7, value: '1234组织者' } });
+
+      wrapper.find('textarea').instance().value = '1234组织者';
+      wrapper.find('textarea').instance().selectionStart = 7;
+      wrapper.find('textarea').simulate('compositionEnd');
+
+      expect(wrapper.find('textarea').at(0).getDOMNode().value).toBe('1234组织');
+    });
+
+    // 2. 光标位于中间或开头，且当前字符数未达到6个，若选中的字符 + 原字符的长度超过6个，则显示原有字符
+    it('when the input method is Pinyin and the cursor is in the middle, should display the original string', () => {
+      const onChange = jest.fn();
+      const wrapper = mount(<TextArea maxLength={6} defaultValue="1234" onChange={onChange} />);
+      wrapper.find('textarea').instance().value = '1234'; // enzyme not support change `currentTarget`
+      wrapper.find('textarea').instance().selectionStart = 2;
+      wrapper.find('textarea').simulate('compositionStart');
+
+      wrapper
+        .find('textarea')
+        .simulate('change', { target: { selectionStart: 2, value: '12z z z34' } });
+      wrapper
+        .find('textarea')
+        .simulate('change', { target: { selectionStart: 5, value: '12组织者34' } });
+
+      wrapper.find('textarea').instance().value = '12组织者34';
+      wrapper.find('textarea').instance().selectionStart = 5;
+      wrapper.find('textarea').simulate('compositionEnd');
+
+      expect(wrapper.find('textarea').at(0).getDOMNode().value).toBe('1234');
+    });
   });
 
   it('when prop value not in this.props, resizeTextarea should be called', async () => {

components/input/demo/textarea.md

@@ -18,5 +18,13 @@ import { Input } from 'antd';
 
 const { TextArea } = Input;
 
-ReactDOM.render(<TextArea rows={4} />, mountNode);
+ReactDOM.render(
+  <>
+    <TextArea rows={4} />
+    <br />
+    <br />
+    <TextArea rows={4} placeholder="maxLength is 6" maxLength={6} />
+  </>,
+  mountNode,
+);
 ```