Explicit DatabaseNotFoundError exception

[German M. Bravo]

Please add an explicit exception for when a database doesn't exist: DatabaseNotFoundError (instead of just DatabaseOpeningError)

Such DatabaseNotFoundError could (and maybe should) inherit from DatabaseOpeningError for backward compatibility.

[Vaibhav Kansagara]

i am working on this one.

[Vaibhav Kansagara]

@olly, To my knowledge this involves: 1)Creating a new class DatabaseNotFoundError in error.h file which inherits DatabaseOpeningError class. 2)Replace all occurrences of DatabaseOpeningError in the code where suitably database is not existing. Specifically i found those occurrences in two files namely dbcheck.cc and dbfactory.cc in the xapian-core/backends. Can you guide me furthur.

[Olly Betts]

Pretty much.

Essentially anywhere that throws DatabaseOpeningError currently needs checking to see if that ought to instead throw the new DatabaseNotFoundError.

But also, some places that currently catch DatabaseOpeningError should be updated correspondingly (especially in the testsuite - note there's a TEST_EXCEPTION(...) macro there as well as explicit catch). The code will still work without this change (since DatabaseNotFoundError is a subclass of DatabaseOpeningError) but we want to have test coverage that the new exception is thrown when it should be.

[Olly Betts]

Fix on git master by 6ba3bf4b1254dadbf3ea4d8c00d3556bd373169f, thanks.

I think we should consider backporting this to 1.4.x as the change is compatible for code catching DatabaseOpeningError, so setting milestone for that and taking ownership.

[Olly Betts]

Backported for 1.4.10 in a4af7a61d4dff7a6ef44b537348091dc4a229da6.

[German M. Bravo]

I added a pull request to complement this with two missing points where I've found DatabaseNotFoundError is needed: ​https://github.com/xapian/xapian/pull/258