Adopt upstream PR #2978: Fix undefined column autofilter assignment

[protobi-pieter]

Summary

Adopt upstream PR exceljs#2978 (partial) to fix crashes when autofilter column index refers to an undefined column.

In some Excel files, the autofilter configuration references column indices that don't exist in the table model, causing crashes when trying to assign the filterButton property to undefined columns.

Upstream PR

• PR: Fix undefined column assignment autofilter exceljs/exceljs#2978
• Author: @hypesystem (Niels Abildgaard)
• Created: 2025-09-25
• Status: Open in upstream

Changes

File modified:

• lib/xlsx/xform/table/table-xform.js - Add guard for undefined columns (3 lines)

Total: 3 additions, 0 deletions

Note: The upstream PR includes additional changes to data-validations-xform.js and package.json. We are only adopting the table-xform.js fix as it's the core bug fix. The other changes are either unrelated or inappropriate for our fork.

Bug Description

When parsing Excel files with autofilter configurations that reference non-existent columns, ExcelJS crashes trying to set properties on undefined objects.

Current behavior:

this.map.autoFilter.model.columns.forEach((column, index) => {
  this.model.columns[index].filterButton = column.filterButton;
  // Crashes if this.model.columns[index] is undefined
});

Fixed behavior:

this.map.autoFilter.model.columns.forEach((column, index) => {
  if (!this.model.columns[index]) {
    return;  // Skip undefined columns
  }
  this.model.columns[index].filterButton = column.filterButton;
});

Value Proposition

• Low Risk - Simple guard clause addition
• Bug Fix - Prevents crashes on malformed Excel files
• Robustness - Improves error handling for edge cases

Testing Plan

• Apply changes from upstream PR (table-xform.js only)
• Run existing test suite
• Verify files with mismatched autofilter indices don't crash

[protobi-pieter]

✅ Complete

This issue was successfully resolved in commit daa210b on November 7, 2025, and closed on November 10, 2025.

Changes Applied

The fix from upstream PR #2978 was applied to lib/xlsx/xform/table/table-xform.js:

Before:

this.map.autoFilter.model.columns.forEach((column, index) => {
  this.model.columns[index].filterButton = column.filterButton;
  // Crashes if this.model.columns[index] is undefined
});

After:

this.map.autoFilter.model.columns.forEach((column, index) => {
  if (!this.model.columns[index]) {
    return;  // Skip undefined columns
  }
  this.model.columns[index].filterButton = column.filterButton;
});

This prevents crashes when autofilter configuration references column indices that don't exist in the table model.

Testing

• ✅ All existing tests pass
• ✅ Code merged to master branch
• ✅ Pushed to remote repository
• ✅ Files with mismatched autofilter indices no longer crash

Checklist Status

• Apply changes from upstream PR (table-xform.js only)
• Run existing test suite
• Verify files with mismatched autofilter indices don't crash

Note: As documented in the issue, we only adopted the core bug fix from table-xform.js, not the additional unrelated changes from the upstream PR.