fix: use strict null/undefined check for display value in single select

[zombieJ]

Empty string values should be treated as valid values (having a display value), not as missing values. This fixes the content-has-value class not being applied when the value is an empty string.

fix ant-design/ant-design#56973

Summary by CodeRabbit

发行说明

• Bug 修复

  • 改进了选择组件中显示值的检测逻辑，确保在空字符串等边界情况下能正确处理和渲染值。

• 测试

  • 增加了新的测试用例，验证组件在特定场景下的 CSS 类应用行为。

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Project	Deployment	Actions	Updated (UTC)
select	Ready	Preview, Comment	Feb 12, 2026 5:23pm

[coderabbitai]

Walkthrough

在 SingleContent.tsx 中引入 hasDisplayValue 守卫变量，用来稳健地检测显示值的存在，取代对 displayValue 的 truthy 检查。该变量被应用于选项数据选择、标题计算、渲染值确定和容器 CSS 类构造等四处。同时添加了测试用例验证空字符串值的样式类应用。

Changes

Cohort / File(s)	Summary
核心逻辑改动 src/SelectInput/Content/SingleContent.tsx	引入 hasDisplayValue 守卫变量替换 displayValue 的 truthy 检查，应用于选项数据选择、标题计算、渲染值和 CSS 类构造，明确处理 null/undefined 情况。
新增测试 tests/placeholder.test.tsx	添加测试用例验证 Select 组件在 value="" 时正确应用 content-has-value CSS 类。

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Possibly related PRs

• refactor: Simplify Select single structure #1195 — 同样修改 SingleContent.tsx 中的选择渲染逻辑和容器类构造，涉及 renderValue/title 的确定。
• fix(Select): fix label not hiding when visibility is set to hidden #1194 — 修改 SingleContent.tsx 中的渲染可见性逻辑，改变显示值的确定和应用方式。
• chore: add more cls #1196 — 修改 SingleContent.tsx 中的类名构造，与本 PR 的 hasDisplayValue 守卫逻辑相关联。

Suggested reviewers

• meet-student

Poem

🐰 空字符串不再捣蛋，
hasDisplayValue 来把关，
高度稳稳保持住，
样式类恰到好处，
测试守护品质翠。

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	Pull request title clearly and specifically describes the main change: introducing strict null/undefined checks for display value in single select component.
Linked Issues check	✅ Passed	The code changes directly address issue #56973 by introducing hasDisplayValue guard to treat empty strings as valid display values, ensuring content-has-value class is applied correctly.
Out of Scope Changes check	✅ Passed	All changes are directly related to fixing the display value check issue; modifications to SingleContent.tsx and addition of placeholder.test.tsx are both in scope.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch refactor/display-value-check

---

No actionable comments were generated in the recent review. 🎉

🧹 Recent nitpick comments

src/SelectInput/Content/SingleContent.tsx (1)

22-22: 可以考虑用宽松等式简化空值检查。

displayValue !== null && displayValue !== undefined 等价于 displayValue != null，后者是 JavaScript/TypeScript 中常见的惯用写法，更简洁。

♻️ 可选简化

-    const hasDisplayValue = displayValue !== null && displayValue !== undefined;
+    const hasDisplayValue = displayValue != null;

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.43%. Comparing base (87e9941) to head (810313b).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1205   +/-   ##
=======================================
  Coverage   99.43%   99.43%           
=======================================
  Files          31       31           
  Lines        1230     1231    +1     
  Branches      441      420   -21     
=======================================
+ Hits         1223     1224    +1     
  Misses          7        7           

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[gemini-code-assist]

Summary of Changes

Hello @zombieJ, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request fixes a rendering bug in the single select component where an empty string value was not recognized as a valid selection, leading to incorrect CSS class application. By implementing a more precise check for the presence of a display value, the component now correctly applies the content-has-value class for all non-null and non-undefined values, including empty strings, thus improving visual consistency and user experience.

Highlights

• Bug Fix: Resolved an issue where empty string values were not correctly treated as valid display values in the single select component, preventing the content-has-value class from being applied.
• Improved Display Value Check: Introduced a new variable hasDisplayValue that strictly checks if displayValue is not null or undefined, ensuring empty strings are considered valid values.
• Test Coverage: Added a new test case to verify that the content-has-value class is correctly applied when the select component's value is an empty string.

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Changelog

• src/SelectInput/Content/SingleContent.tsx
  • Introduced a new hasDisplayValue variable to strictly check for null or undefined display values.
  • Updated conditional logic for rendering and class application to use hasDisplayValue instead of direct displayValue truthiness.
• tests/placeholder.test.tsx
  • Added a test case to confirm that the .rc-select-content-has-value class is present when the Select component has an empty string as its value.

Activity

• A summary was auto-generated by coderabbit.ai, highlighting the bug fix in the select component's display value detection and the addition of new test cases for CSS class application.

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[gemini-code-assist]

Code Review

This pull request addresses a bug where empty string values in the single select component were not being treated as valid, leading to incorrect rendering. The change to use a strict check for null and undefined to determine the presence of a display value is the correct approach, as it properly handles falsy values like empty strings. The introduction of the hasDisplayValue constant is a good refactoring that improves code clarity and maintainability. Additionally, the new test case effectively verifies the fix. The changes are well-implemented and resolve the reported issue.