Blog Series: TableFlip's NSDocument File Type Issues and Fixes

This is an overview of a short series of posts I wrote about TableFlip’s 2020 bug. People were getting a “You don’t have permissions” error, a Sandboxing error, when they worked with .txt files, but not with .md files, even though the app treated them the same. The issue boiled down to a misconfiguration on my side that went by unnoticed until I enabled Sandboxing. I was wrongly defining document types in the app’s Info.plist, and I was reporting supported file types in the NSDocument subclass in a manner that didn’t work out well.

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Programmatically Select a NSSavePanel File Format to Fix Empty Selections

In my quest to vanquish bugs from TableFlip, we intially observed that file extensions would attempt to change after an external file change. It turnes out that this was my fault because I effectively always passed "net.daringfireball.markdown", even when the document type originally was "public.plain-text". Passing the wrong file type to NSDocument.revert(toContentsOf:ofType:) was causing the issue. Trying to use the optional NSDocument.fileType property first, and then providing a fallback, solved the file extension problem.

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