Many commands and plugins use `item.write()` to update tags. Since the success
of the call is not critical to the functionality of most consumers we want to
catch any exceptions, log an error and continue with our task. The new method
encapsulates this logic.
This fixes#675.
bs4 scraping routine has been made more generic,
relying less on specific markup tags.
Better algorithm to detect which url titles match
song titles: domain names are now removed from url
titles.
Use regex to decimate \n in fetched lyrics.
Add a 'fallback' option to facilitate working around the 100 queries/day google
limit by marking files as 'visited' so they are not considered for lyrics search
on the next beet run.
I've put my own google_engine_ID as default value in the code but could be
reconsidered, this engine contains databases known to be scrappable by the
plugin algorithm though.
A user reported a problem with one of the logging statements where .format()
tried to convert a Unicode string to bytes because the log message was '', not
u''. As a rule, we should ensure that all logging statements use Unicode
literals.
In an attempt to finally address the longstanding SQLite locking issues, I'm
introducing a way to explicitly, lexically scope transactions. The Transaction
class is a context manager that always fully fetches after SELECTs and
automatically commits on exit. No direct access to the library is allowed, so
all changes will eventually be committed and all queries will be completed. This
will also provide a debugging mechanism to show where concurrent transactions
are beginning and ending.
To support composition (transaction reentrancy), an internal, per-Library stack
of transactions is maintained. Commits only happen when the outermost
transaction exits. This means that, while it's possible to introduce atomicity
bugs by invoking Library methods outside of a transaction, you can conveniently
call them *without* a currently-active transaction to get a single atomic
action.
Note that this "transaction stack" concepts assumes a single Library object per
thread. Because we need to duplicate Library objects for concurrent access due
to sqlite3 limitation already, this is fine for now. Later, the interface should
provide one transaction stack per thread for shared Library objects.
