Does the specification define input[type=file] .file... | w3c/FileAPI

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Consider the HTML and JavaScript posted at this Stack Overflow question Input file size and content do not update on macOS

HTML

<!DOCTYPE html>
<input type="file" id="file" />
<p id="info"></p>

JavaScript

window.addEventListener('load', function() {
  window.setInterval(function() {
    var logFile = document.querySelector('#file').files[0];
    if (logFile) {
      document.querySelector('#info').innerHTML = '<br/>' +
        (new Date()).toString() + '<br/>Last modified: ' +
        logFile.lastModified +
        '<br/>Size: ' +
        logFile.size;
    }
  }, 1000);
});

Reproduce steps as described by OP of the question

Please test with following snippet. Select a file (for example a text file), see last modified timestamp and file size, then change file and look again, if size has changed. On macOS the file size doesn't change.

Using a sample file, for example, https://gist.github.com/guest271314/11edc4566ba94f204dd46e6ae26edaad#file-d134213ba9465cb74dfd36cde47bf102638c4a9f3aca357f79ee747dd5f49f1e0f0de , which contains the text

123

Behaviour

Chromium 65

Once the local file is selected by user action and the local file is changed at a text editor, for example, by typing 4 following the existing 123 at the file (for example, the above linked gist) both lastModified and size properties are reflected as being changed client side, indicating changes to local file are being updated in real time though the user has not performed the affirmative action of re-selecting the file.

Firefox Trunk (60)

Once the local file is selected by user action and the local file is changed at a text editor, for example, by typing 4 following the existing 123 at the file (for example, the above linked gist) both lastModified and size properties are not reflected as being changed client side, indicating changes to local file are being not updated in real time where the user has not performed the affirmative action of re-selecting the file.

What does the specification define as the expected behaviour of size and lastModified properties of a File object within a FileList object where changes to an underlying local file are made after user selection of a local file?

Review the File API definitions for File and FileList, then compare their requirements with the linked Stack Overflow reproduction and the Chromium 65 and Firefox Trunk observations. Done means determining whether post-selection changes to a local file's size and lastModified must be reflected, and documenting or clarifying the specification accordingly.

Written by the indexing model from the issue text.

Does the specification define input[type=file] .files expected behaviour to relevant to reflecting real-time changes to user selected file?

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