Fix TypeError when selecting autocomplete on empty masked input

[Copilot]

Selecting a browser autocomplete suggestion on an empty masked input throws TypeError: Cannot read properties of undefined (reading 'length') inside keyEvent.

Root Cause

analyseChanges in inputFallBackEvent misclassifies the input event as "deleteContentBackward" when:

• caret is at position 0 (browser behavior after autofill in some cases)
• mask template buffer is longer than the autocomplete value

This causes backPart to be front-padded with marker characters (~) to match buffer length. The leading marker in newBuffer[0] hits condition 4 in the comparison loop → action = "deleteContentBackward". The code then dispatches a synthetic Backspace keydown, which cascades into the TypeError inside keyEvent.

Fix

In the "deleteContentBackward" switch case of inputFallBackEvent, guard against the contradiction where e.inputType signals an insertion (e.g. "insertReplacementText" from browser autocomplete) but analyseChanges returned a deletion. In that case, call applyInputValue directly instead of dispatching the erroneous Backspace event.

case "deleteContentBackward":
  if (e.inputType && e.inputType.startsWith("insert")) {
    // analyseChanges misdetected deletion due to caret/buffer length mismatch
    applyInputValue(input, inputValue);
    caret.call(inputmask, input, caretPos.begin, caretPos.end, true);
  } else {
    var keydown = new $.Event("keydown");
    keydown.key = keys.Backspace;
    EventHandlers.keyEvent.call(input, keydown);
  }
  break;

Legitimate deleteContentBackward events (where e.inputType is "deleteContentBackward" or absent) are unaffected.

Test Case

A regression test has been added to the QUnit suite to verify the fix:

• qunit/simulator.js – new $.fn.autocomplete(value, caretBegin, caretEnd) helper that sets the native input value and fires an input event with inputType: "insertReplacementText", matching real browser autocomplete behaviour.
• qunit/tests_inputeventonly.js – new test "(999) 999-9999 - autocomplete on empty input (insertReplacementText)" that simulates selecting an autocomplete suggestion on a fresh empty (999) 999-9999 masked input (caret at position 0) and asserts both that no error is thrown and that the value is correctly formatted as (123) 123-1234.

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[RobinHerbots]

Don't update this file as It will be updated by the build process automatically.

[Copilot]

Reverted in 30f5dbf.

[RobinHerbots]

@copilot ,
Exclude updates in the dist folder. Only keep updates in the lib folder and the changelog

[Copilot]

@copilot ,
Exclude updates in the dist folder. Only keep updates in the lib folder and the changelog

Done in 30f5dbf — dist files and inputmask-pages/src/assets/Changelog.md have been removed from the PR. Only lib/eventhandlers.js and the root Changelog.md are changed.

[RobinHerbots]

@copilot ,

Can you workout a testcase, so it is easier to test the changes. Ex a codepen link or simular.

[Copilot]

@copilot ,

Can you workout a testcase, so it is easier to test the changes. Ex a codepen link or simular.

Added a regression test in commit c781c07:

• qunit/simulator.js – new $.fn.autocomplete(value, caretBegin, caretEnd) helper that sets the native value and fires an input event with inputType: "insertReplacementText", matching real browser autocomplete behaviour.
• qunit/tests_inputeventonly.js – new test "(999) 999-9999 - autocomplete on empty input (insertReplacementText)" that applies the helper to a fresh empty masked input (caret at 0) and asserts both that no error is thrown and that the value is formatted correctly as (123) 123-1234.

To run it manually you can also open qunit/qunit.html in a browser and use a local server (the test will appear under the inputEventOnly: true module).