Include import of __future__ features division, absolute_imports and
print_function everywhere. Don't add unicode_literals yet for it is
harder to convert.
Goal is smoothing the transition to python 3.
So far an invalid query won't be applied:
$ beet ls The Beatles year:196a
will be treaded as
$ beet ls The Beatles
With this commit it stops beets, returns 1 and produces
$ invalid query: u'196a' is not an int or a float
This applies to any querying and therefore on many command, plugins and
some configuration options.
Invalid queries exist on numeric fields and on regular expression usage.
Compile regular expression queries upon instantiation instead of upon
each match test.
The reporting can be improved (give more context). Fix#1219.
The initial idea for this refactor was motivated by the need to make
PluginQuery.match() have the same method signature as the match() methods on
other queries. That is, it needed to take an *item*, not the pattern and
value. (The pattern is supplied when the query is constructed.) So it made
sense to move the value-to-pattern code to a class method.
But then I realized that all the other FieldQuery subclasses needed to do
essentially the same thing. So I eliminated PluginQuery altogether and
refactored FieldQuery to subsume its functionality. I then changed all the
other FieldQuery subclasses to conform to the same pattern.
This has the side effect of allowing different kinds of queries (even
non-field queries) down the road.
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.
