WIP Xlsx Reader Vml File with Unclosed br Tags

[oleibman]

Fix #3125 (rejected previous PR #1181 as too risky, issue was also reported as #170). Vml file should be valid Xml, but Excel (possibly just Excel 2013) can generate unclosed <br> tags, preventing Xlsx reader from reading file correctly. I believe a very narrowly targeted fix, changing <br> to <br/>, and only when reading vml files, probably mitigates the risk. I am going to leave this PR as a draft for a while to see if others disagree.

Another reason to leave it as a draft is the absence of a decent test file. I am able to copy an existing test spreadsheet which contains a vml file, and add some text and the problematic tag, and I can confirm that it fails to load correctly without the fix but loads correctly with the fix. However, it would be better if I had a real file. I cannot figure out how to generate a file like this "naturally"; when I add a textbox to a spreadsheet, it is stored as a regular xml file, not as vml, in both Excel 365 and 2007. Also, the text that I added in the vml file doesn't show anywhere when I open the file in Excel, so I don't know whether my file is a normal case for this condition. And, incidentally, when I load the file in PhpSpreadsheet and save it, the textbox data is not in the resulting output file; this is clearly not a problem in the particular case I constructed, but I don't know if that's true in general. If not, that would be a different problem than the one I'm fixing, but I would prefer to resolve them both at the same time.

This is:

- [x] a bugfix
- [ ] a new feature
- [ ] refactoring
- [x] additional unit tests

Checklist:

• Changes are covered by unit tests
  • Changes are covered by existing unit tests
  • New unit tests have been added
• Code style is respected
• Commit message explains why the change is made (see https://github.com/erlang/otp/wiki/Writing-good-commit-messages)
• CHANGELOG.md contains a short summary of the change
• Documentation is updated as necessary

Why this change is needed?

Provide an explanation of why this change is needed, with links to any Issues (if appropriate).
If this is a bugfix or a new feature, and there are no existing Issues, then please also create an issue that will make it easier to track progress with this PR.

[fglueck]

the fix

is only one problem. I also get some more failures like:

• Opening and ending tag mismatch: font line 56 and div
• Opening and ending tag mismatch: div line 56 and v:textbox
• Opening and ending tag mismatch: textbox line 55 and shape
• Opening and ending tag mismatch: shape
• Premature end of data in tag shape

My workaround:
$objReader->getSecurityScanner()->setAdditionalCallback(fn ($xml) => tidy_repair_string($xml, ['input-xml'=>true]));

I use phpSpreadsheet a lot of years, but this problem is new.

[oleibman]

I have managed to create a spreadsheet with this problem. Excel 365 continues to generate unclosed br tags; the problem is not limited to Excel 2013 after all. But ... in order to deal with all the moving parts, I need the code added by draft PR #2455 (form controls). I think it is probably best to proceed by adding the changes from that PR to this one, and closing the original. Or possibly by creating a third ticket, and closing this and 2455. I'll try to get something ready over the next few days.

[oleibman]

Closing, superseded by PR #3130.