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122 lines
3.8 KiB
Python
122 lines
3.8 KiB
Python
"""Allows inline path template customization code in the config file."""
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import itertools
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import traceback
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from beets import config
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from beets.plugins import BeetsPlugin
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FUNC_NAME = "__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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def __init__(self, code, exc):
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super().__init__(
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f"error in inline path field code:\n{code}\n{type(exc).__name__}: {exc}"
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)
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def _compile_func(body, args=""):
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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 = body.replace("\n", "\n ")
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body = f"def {FUNC_NAME}({args}):\n {body}"
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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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class InlinePlugin(BeetsPlugin):
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def __init__(self):
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super().__init__()
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config.add(
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{
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"pathfields": {}, # Legacy name.
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"item_fields": {},
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"album_fields": {},
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}
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)
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# Item fields.
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for key, view in itertools.chain(
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config["item_fields"].items(), config["pathfields"].items()
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):
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self._log.debug("adding item field {}", key)
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func = self.compile_inline(view.as_str(), False, key)
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if func is not None:
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self.template_fields[key] = func
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# Album fields.
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for key, view in config["album_fields"].items():
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self._log.debug("adding album field {}", key)
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func = self.compile_inline(view.as_str(), True, key)
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if func is not None:
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self.album_template_fields[key] = func
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def compile_inline(self, python_code, album, field_name):
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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(f"({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, args="db_obj")
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except SyntaxError:
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self._log.error(
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"syntax error in inline field definition:\n{}",
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traceback.format_exc(),
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)
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return None
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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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def _dict_for(obj):
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out = {}
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for key in obj.keys(computed=False):
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if key == field_name:
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continue
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out[key] = obj._get(key)
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if album:
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out["items"] = list(obj.items())
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return out
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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(obj):
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values = _dict_for(obj)
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values["db_obj"] = obj
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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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# For function bodies, invoke the function with values as global
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# variables.
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def _func_func(obj):
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old_globals = dict(func.__globals__)
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func.__globals__.update(_dict_for(obj))
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try:
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return func(obj)
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except Exception as exc:
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raise InlineError(python_code, exc)
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finally:
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func.__globals__.clear()
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func.__globals__.update(old_globals)
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return _func_func
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