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a0cb31956d
An earlier change (due to @pedros) added the ability for plugins to define template fields that work with Albums as well as Items. This enables some cool new use cases but required that every template field definition check the type of its arguments. Instead, this iteration on the idea distinguishes between fields meant for Items and those meant for Albums. In addition to simplifying the implementation of these functions, this also enables the creation of album fields with identical names to item fields. (For example, a user contacted me recently about adding a $bitrate field for albums, which would be the average bitrate of the items. They can do this now using a plugin.) I also changed the docs to stop using the decorator approach to registering template fields. We're moving toward removing those.
104 lines
3.4 KiB
Python
104 lines
3.4 KiB
Python
# This file is part of beets.
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# Copyright 2013, Adrian Sampson.
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#
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# Permission is hereby granted, free of charge, to any person obtaining
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# a copy of this software and associated documentation files (the
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# "Software"), to deal in the Software without restriction, including
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# without limitation the rights to use, copy, modify, merge, publish,
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# distribute, sublicense, and/or sell copies of the Software, and to
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# permit persons to whom the Software is furnished to do so, subject to
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# the following conditions:
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#
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# The above copyright notice and this permission notice shall be
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# included in all copies or substantial portions of the Software.
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"""Allows inline path template customization code in the config file.
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"""
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import logging
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import traceback
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from beets.plugins import BeetsPlugin
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from beets import config
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log = logging.getLogger('beets')
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FUNC_NAME = u'__INLINE_FUNC__'
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class InlineError(Exception):
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"""Raised when a runtime error occurs in an inline expression.
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"""
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def __init__(self, code, exc):
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super(InlineError, self).__init__(
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(u"error in inline path field code:\n" \
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u"%s\n%s: %s") % (code, type(exc).__name__, unicode(exc))
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)
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def _compile_func(body):
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"""Given Python code for a function body, return a compiled
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callable that invokes that code.
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"""
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body = u'def {0}():\n {1}'.format(
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FUNC_NAME,
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body.replace('\n', '\n ')
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)
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code = compile(body, 'inline', 'exec')
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env = {}
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eval(code, env)
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return env[FUNC_NAME]
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def compile_inline(python_code):
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"""Given a Python expression or function body, compile it as a path
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field function. The returned function takes a single argument, an
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Item, and returns a Unicode string. If the expression cannot be
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compiled, then an error is logged and this function returns None.
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"""
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# First, try compiling as a single function.
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try:
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code = compile(u'({0})'.format(python_code), 'inline', 'eval')
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except SyntaxError:
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# Fall back to a function body.
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try:
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func = _compile_func(python_code)
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except SyntaxError:
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log.error(u'syntax error in inline field definition:\n%s' %
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traceback.format_exc())
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return
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else:
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is_expr = False
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else:
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is_expr = True
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if is_expr:
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# For expressions, just evaluate and return the result.
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def _expr_func(item):
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values = dict(item.record)
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try:
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return eval(code, values)
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except Exception as exc:
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raise InlineError(python_code, exc)
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return _expr_func
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else:
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# For function bodies, invoke the function with values as global
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# variables.
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def _func_func(item):
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func.__globals__.update(item.record)
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try:
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return func()
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except Exception as exc:
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raise InlineError(python_code, exc)
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return _func_func
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class InlinePlugin(BeetsPlugin):
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def __init__(self):
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super(InlinePlugin, self).__init__()
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config.add({
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'pathfields': {},
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})
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# Add field expressions.
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for key, view in config['pathfields'].items():
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log.debug(u'adding template field %s' % key)
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func = compile_inline(view.get(unicode))
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if func is not None:
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self.template_fields[key] = func
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