Fix#4248. PhpSpreadsheet has used what appear to be default attributes and tags when they are missing from Fill patterns and colors. However, Excel handles their absence a little differently from what the "default" would require. PhpSpreadsheet is changed to omit the attributes and tags in question when missing. This change is mostly targeted towards Xlsx read and write, but minor changes for Xls and Html write are also included.
This seems like it could be a breaking change, but I don't think it is. One test (DefaultFillTest introduced by PR #2050) must change, but the change is internal - loading and then saving the spreadsheet used in that change will appear the same after this change as it did before. Other differences are very likely to be bug fixes rather than breaks.
While we might never be able to have 100% of our code strict, we can at
the very least do it for all of our tests. This ensures that our tests
are using our API with the types as intended by the test author, and not
silently be cast to what our API requires.
* Let's see if the tests now pass against PHP8; output file looks to be good
* Font can't be both superscript and subscript at the same time, so we use if/else rather than if/if
* Pattern Fill style should default to 'solid' if there is a pattern fill style for a conditional; though may need to check if there are defined fg/bg colours as well; and only set a fill style if there are defined colurs
Openpyxl can generate the xml tag `<patternFill/>`, possibly even as a default style. Excel has no problem with this, treating it as "fill none", but PhpSpreadsheet has a glitch because it treats it as "fill solid white". So, when PhpSpreadsheet loads and saves such a file, the result at first appears as if gridlines are disabled; in fact, the gridlines are merely invisible behind the cells with their solid white fill. This PR makes PhpSpreadsheet behave the same as Excel in this circumstance.
Co-authored-by: Mark Baker <mark@lange.demon.co.uk>
oleibman
Adrien Crivelli
Mark Baker
oleibman