When Legacy Justifies Errors

Since forever, Basic in OpenOffice.org had a bug: it didn’t properly check closing parentheses in expressions like

FirstUpper = UCase( Left( sString, 1 ) + LCase( Mid( sString, 2 ) )

(example taken from this AskLibO question). Note the mismatch between opening and closing parentheses: four opening, and only three closing. The author missed one to close UCase function after Left( sString, 1 ), and any compiler would naturally point out to this common mistake – any but StarBasic in OOo and derivatives.

What StarBasic did was auto-closing the expression in the end when compiling. It would only complain if the result of such auto-closing would be ill-formed; sometimes (as in the example above), the result would be syntactically correct – but not necessarily semantically correct: the example above compiled with StarBasic did not what author expected (a text with first character capitalized, and the rest of the text in lowercase), but returned text in all caps instead. For some similar cases, such errors could be not easy to find in the absence of compiler check, especially in a large project.

This has been reported to LibreOffice bug tracker as tdf#80731 back in 2014; and it was addressed in 5.4 development cycle, with the fix backported into 5.3.1. A nice and correct fix, isn’t it?

Well, not actually. It turned out, that over the years, the amount of existing and actually used legacy code having the error has become so big, that it was unrealistic to make sure that all of it is checked and fixed. Of course, some errors were found in the code bundled with LibreOffice itself – and naturally, it was fixed. Some third-party extensions – quite a number of them – also happened to have it; and all authors who could be contacted, had released updated releases with the mistake corrected; thank you! But it wasn’t possible to test any extension out there; and besides publicly available and supported extensions, there were also unsupported (but still used, and useful) ones; and private ones (used by those who developed/paid for their development); and also uncountable macros outside of any extensions, and all of them having the error, that happily worked before, suddenly stopped working for their users … so after some time, the fix was reverted both from 5.3.3, and from still developing 5.4 (tdf#106529). By the way, I was enjoying reading “AltSearch extension put a bugfix release 1.4.2 to work around this bug” there, as if pointing to syntax error was actually a LibreOffice’s bug, not a mistake in the extension’s code.

So LibreOffice kept silently allowing the wrong syntax ever after 5.3.3, until now. Today I have reinstated the original fix by Pierre Lepage from 5.4, with one modification: the check is only active when compiling the code from within Basic IDE. What does it mean? It means, that for anyone writing a new code in the Basic IDE, the syntax error will be properly found and shown. When one opens an existing module in the IDE, and makes a modification (which would of course trigger recompilation), the existing errors in the same module (even in different routines) would be found, too. But if the code is compiled not from the IDE (as when a macro is executed from an event handler; or when an extension runs its code), the old permissive handling is kept, and the code with errors will continue working as before.

I consider this an acceptable compromise, which would both allow existing users of legacy code to keep using their code, and still prevent creation of new buggy code (and also help gradually cleaning up the existing errors in supported Basic programs).

The change will appear in coming version 6.4. It’s still to be seen if this change will survive, or will it also uncover a different can of worms, and be eventually reverted, as its predecessor 😊