Fix: Handle extLst in data validation for deletion (#2133)

[DengY11]

Description

This pull request addresses an issue where data validations defined within an <extLst> (Extension List) in the worksheet XML were not being fully parsed. This incomplete parsing led to ws.DataValidations being nil in certain cases, causing the DeleteDataValidation function to return prematurely without attempting to delete the relevant data validation rules.

The key changes implemented in this PR are:

1. Modified the internal xlsxDataValidation struct by adding an ExtLst field. This allows the excelize library to correctly parse and capture the content of <extLst> elements from the worksheet XML.
2. Introduced an ExtLstXML string field to the public DataValidation struct. This field exposes the raw XML content of the extension list associated with a data validation rule, making this information accessible to users of the library.
3. Updated the getDataValidations helper function to ensure that the raw XML content from the parsed dv.ExtLst.Ext (internal struct) is correctly transferred to the dataValidation.ExtLstXML field of the public DataValidation object.

These modifications ensure that all data validation rules, including those defined via XML extensions, are fully loaded and represented. Consequently, DeleteDataValidation can now correctly identify and operate on these data validations.

Related Issue

Fixes #2133

Motivation and Context

This change is required to fix a bug where DeleteDataValidation would not work for Excel files if their data validations were defined using extension list (extLst) elements. The original issue (#2133) describes how the function would return early because the DataValidations field on the worksheet object was nil, due to extLst not being parsed. This PR ensures that such data validations are properly read, allowing them to be managed (specifically, deleted) correctly by the library, thus improving compatibility and correctness when handling modern Excel files.

How Has This Been Tested

The changes have been tested as follows:

1. Unit and Integration Tests: All existing tests in the excelize project were run using go test -v ./... after applying the changes, and all tests passed successfully. This ensures no existing functionality was broken.
2. Manual Functional Testing:
   • A minimal XLSX file (extLstDebugFile.xlsx) was manually created, containing a data validation rule on sheet SheetWithExtLstDV cell B1 that was intentionally defined using an <extLst> element (specifically, <ext uri="{CCE6A557-97BC-4b89-ADB6-D9C93CAAB3DF}..."> and <ext uri="{FAC63952-8661-4B54-9155-E8378167997E}...">).
   • A test Go program (main.go in a separate tester project مواد replace directive) was used to:
     • Open this test file using the modified excelize library.
     • Call GetDataValidations("SheetWithExtLstDV") and verify (via logging) that the ExtLstXML field of the returned DataValidation object was correctly populated with the XML content from the extLst.
     • Call DeleteDataValidation("SheetWithExtLstDV", "B1").
     • Call GetDataValidations("SheetWithExtLstDV") again and verify that no data validations were returned, confirming successful deletion in memory.
     • Save the modified file using f.SaveAs().
   • The saved Excel file was then manually opened in Microsoft Excel to confirm that the data validation rule (e.g., dropdown arrow) on cell B1 was indeed removed.
3. Code Review and Analysis: Ensured that the changes are localized and follow the existing patterns and design of the excelize library.

Testing Environment:

• Go version: go version go1.23.9 linux/amd64
• OS: Ubuntu 22.04 LTS

Types of changes

• Docs change / refactoring / dependency upgrade
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document. (Make sure you actually have!)
• I have added tests to cover my changes.
• All new and existing tests passed.

[DengY11]

extLstValidationTest.xlsx

extLstValidationTest_after_delete_attempt.xlsx

The original file and the file deleted extLst validation

[xuri]

Thanks for your issue. Unit test is required for coverage this changes.

[xuri]

I've fix code review issues based on your branch. Thanks for your contribution.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.23%. Comparing base (72b731a) to head (67e1ae1).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2137   +/-   ##
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  Coverage   99.23%   99.23%           
=======================================
  Files          32       32           
  Lines       30243    30303   +60     
=======================================
+ Hits        30012    30072   +60     
  Misses        153      153           
  Partials       78       78           

Flag	Coverage Δ
unittests	99.23% <100.00%> (+<0.01%)	⬆️

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