RFC: inline: make the album/item available directly

beetsplug/inline.py

@@ -33,11 +33,13 @@ def __init__(self, code, exc):
         )
 
 
-def _compile_func(body):
+def _compile_func(body, args=""):
     """Given Python code for a function body, return a compiled
     callable that invokes that code.
     """
-    body = "def {}():\n    {}".format(FUNC_NAME, body.replace("\n", "\n    "))
+    body = "def {}({}):\n    {}".format(
+        FUNC_NAME, args, body.replace("\n", "\n    ")
+    )
     code = compile(body, "inline", "exec")
     env = {}
     eval(code, env)
@@ -84,7 +86,9 @@ def compile_inline(self, python_code, album):
         except SyntaxError:
             # Fall back to a function body.
             try:
-                func = _compile_func(python_code)
+                func = _compile_func(
+                    python_code, args="album" if album else "item"
+                )
             except SyntaxError:
                 self._log.error(
                     "syntax error in inline field definition:\n" "{0}",
@@ -106,6 +110,7 @@ def _dict_for(obj):
             # For expressions, just evaluate and return the result.
             def _expr_func(obj):
                 values = _dict_for(obj)
+                values["album" if album else "item"] = obj
                 try:
                     return eval(code, values)
                 except Exception as exc:
@@ -119,7 +124,7 @@ def _func_func(obj):
                 old_globals = dict(func.__globals__)
                 func.__globals__.update(_dict_for(obj))
                 try:
-                    return func()
+                    return func(obj)
                 except Exception as exc:
                     raise InlineError(python_code, exc)
                 finally:

docs/changelog.rst

@@ -23,6 +23,8 @@ New features:
 * Beets now uses ``platformdirs`` to determine the default music directory.
   This location varies between systems -- for example, users can configure it
   on Unix systems via ``user-dirs.dirs(5)``.
+* :doc:`plugins/inline`: Add access to the ``album`` or ``item`` object in
+  inline fields.
 
 Bug fixes:
 

docs/plugins/inline.rst

@@ -13,7 +13,10 @@ new template field; the key is the name of the field (you'll use the name to
 refer to the field in your templates) and the value is a Python expression or
 function body. The Python code has all of a track's fields in scope, so you can
 refer to any normal attributes (such as ``artist`` or ``title``) as Python
-variables.
+variables. The Python code also has direct access to the item object as ``item``
+for item fields, and as ``album`` for album fields. This allows use of computed
+fields and plugin fields, for example, ``album.albumtotal``, or ``album.missing``
+if the :doc:`/plugins/missing` plugin is enabled.
 
 Here are a couple of examples of expressions::