Upgrade to Python 3.8 / drop Python 3.7 (#5283)

## Description

Fixes #5222. 

Drop Python 3.7. `pyupgrade` is responsible for most of the changes in
the code. I undid some of the bits it attempted to update that aren't
strictly necessary:

1. Converting `List/Dict/Tuple` -> `list/dict/tuple` in modules that
have `from __future__ import annotations` import. This should be done in
a separate PR, and for all modules
2. Converting some `.format(` calls to f-strings. It didn't do it
consistently, and it should also be done in a separate PR, I believe.

Python upgrade unblocks several other PRs, for example #5266 and #5248.

.github/workflows/ci.yaml

@@ -12,7 +12,7 @@ jobs:
     strategy:
       matrix:
         platform: [ubuntu-latest, windows-latest]
-        python-version: ['3.7', '3.8', '3.9', '3.x']
+        python-version: ["3.8", "3.9", "3.x"]
 
     env:
       PY_COLORS: 1
@@ -25,15 +25,7 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
 
-      # tox fails on Windows if version > 3.8.3
-      - name: Install base dependencies - Windows
-        if: matrix.platform == 'windows-latest'
-        run: |
-          python -m pip install --upgrade pip
-          python -m pip install tox==3.8.3 sphinx
-
-      - name: Install base dependencies - Ubuntu
-        if: matrix.platform != 'windows-latest'
+      - name: Install base dependencies
         run: |
           python -m pip install --upgrade pip
           python -m pip install tox sphinx
@@ -50,7 +42,7 @@ jobs:
           tox -e py-test
 
       - name: Upload code coverage
-        if: matrix.python-version == '3.7' && matrix.platform == 'ubuntu-latest'
+        if: matrix.python-version == '3.8' && matrix.platform == 'ubuntu-latest'
         run: |
           pip install codecov || true
           codecov || true
@@ -76,7 +68,7 @@ jobs:
       - name: Set up Python 3.x
         uses: actions/setup-python@v2
         with:
-          python-version: '3.x'
+          python-version: "3.x"
 
       - name: Install base dependencies
         run: |
@@ -98,7 +90,7 @@ jobs:
       - name: Set up Python 3.x
         uses: actions/setup-python@v2
         with:
-          python-version: '3.x'
+          python-version: "3.x"
 
       - name: Install base dependencies
         run: |

CONTRIBUTING.rst

@@ -282,7 +282,7 @@ Running the Tests
 
 To run the tests for multiple Python versions, compile the docs, and
 check style, use `tox`_. Just type ``tox`` or use something like
-``tox -e py27`` to test a specific configuration. You can use the
+``tox -e py38`` to test a specific configuration. You can use the
 ``--parallel`` flag to make this go faster.
 
 You can disable a hand-selected set of "slow" tests by setting the
@@ -294,13 +294,6 @@ Other ways to run the tests:
 -  ``python -m unittest discover -p 'test_*'`` (ditto)
 -  `pytest`_
 
-You can also see the latest test results on `Linux`_ and on `Windows`_.
-
-Note, if you are on Windows and are seeing errors running tox, it may be related to `this issue`_,
-in which case you may have to install tox v3.8.3 e.g. ``python -m pip install tox==3.8.3``
-
-.. _this issue: https://github.com/tox-dev/tox/issues/1550
-
 Coverage
 ^^^^^^^^
 
@@ -360,9 +353,6 @@ others. See `unittest.mock`_ for more info.
 .. _pytest-random: https://github.com/klrmn/pytest-random
 .. _tox: https://tox.readthedocs.io/en/latest/
 .. _pytest: https://docs.pytest.org/en/stable/
-.. _Linux: https://github.com/beetbox/beets/actions
-.. _Windows: https://ci.appveyor.com/project/beetbox/beets/
-.. _`https://github.com/beetbox/beets/blob/master/setup.py#L99`: https://github.com/beetbox/beets/blob/master/setup.py#L99
 .. _test: https://github.com/beetbox/beets/tree/master/test
 .. _`https://github.com/beetbox/beets/blob/master/test/test_template.py#L224`: https://github.com/beetbox/beets/blob/master/test/test_template.py#L224
 .. _unittest: https://docs.python.org/3/library/unittest.html

beets/autotag/mb.py

@@ -598,7 +598,7 @@ def album_info(release: Dict) -> beets.autotag.hooks.AlbumInfo:
     # Media (format).
     if release["medium-list"]:
         # If all media are the same, use that medium name
-        if len(set([m.get("format") for m in release["medium-list"]])) == 1:
+        if len({m.get("format") for m in release["medium-list"]}) == 1:
             info.media = release["medium-list"][0].get("format")
         # Otherwise, let's just call it "Media"
         else:

beets/dbcore/types.py

@@ -14,32 +14,22 @@
 
 """Representation of type information for DBCore model fields.
 """
-import sys
 import typing
 from abc import ABC
-from typing import TYPE_CHECKING, Any, Generic, List, TypeVar, Union, cast
+from typing import Any, Generic, List, TypeVar, Union, cast
 
 from beets.util import str2bool
 
 from .query import BooleanQuery, FieldQuery, NumericQuery, SubstringQuery
 
-# Abstract base.
 
+class ModelType(typing.Protocol):
+    """Protocol that specifies the required constructor for model types,
+    i.e. a function that takes any argument and attempts to parse it to the
+    given type.
+    """
 
-# FIXME: unconditionally define the Protocol once we drop Python 3.7
-if TYPE_CHECKING and sys.version_info >= (3, 8):
-
-    class ModelType(typing.Protocol):
-        """Protocol that specifies the required constructor for model types,
-        i.e. a function that takes any argument and attempts to parse it to the
-        given type.
-        """
-
-        def __init__(self, value: Any = None): ...
-
-else:
-    # No structural subtyping in Python < 3.8...
-    ModelType = Any
+    def __init__(self, value: Any = None): ...
 
 
 # Generic type variables, used for the value type T and null type N (if

beets/library.py

@@ -22,6 +22,7 @@
 import sys
 import time
 import unicodedata
+from functools import cached_property
 
 from mediafile import MediaFile, UnreadableFileError
 
@@ -31,7 +32,6 @@
 from beets.util import (
     MoveOperation,
     bytestring_path,
-    lazy_property,
     normpath,
     samefile,
     syspath,
@@ -436,11 +436,11 @@ def __init__(self, item, included_keys=ALL_KEYS, for_path=False):
             self.model_keys = included_keys
         self.item = item
 
-    @lazy_property
+    @cached_property
     def all_keys(self):
         return set(self.model_keys).union(self.album_keys)
 
-    @lazy_property
+    @cached_property
     def album_keys(self):
         album_keys = []
         if self.album:

beets/logging.py

@@ -22,7 +22,6 @@
 
 
 import logging
-import sys
 import threading
 from copy import copy
 
@@ -84,12 +83,7 @@ def _log(
         m = self._LogMessage(msg, args, kwargs)
 
         stacklevel = kwargs.pop("stacklevel", 1)
-        if sys.version_info >= (3, 8):
-            stacklevel = {"stacklevel": stacklevel}
-        else:
-            # Simply ignore this when not supported by current Python version.
-            # Can be dropped when we remove support for Python 3.7.
-            stacklevel = {}
+        stacklevel = {"stacklevel": stacklevel}
 
         return super()._log(
             level,

beets/ui/commands.py

@@ -90,7 +90,7 @@ def _paths_from_logfile(path):
     """Parse the logfile and yield skipped paths to pass to the `import`
     command.
     """
-    with open(path, mode="r", encoding="utf-8") as fp:
+    with open(path, encoding="utf-8") as fp:
         for i, line in enumerate(fp, start=1):
             verb, sep, paths = line.rstrip("\n").partition(" ")
             if not sep:
@@ -117,7 +117,7 @@ def _parse_logfiles(logfiles):
                     util.displayable_path(logfile), str(err)
                 )
             ) from err
-        except IOError as err:
+        except OSError as err:
             raise ui.UserError(
                 "unreadable logfile {}: {}".format(
                     util.displayable_path(logfile), str(err)
@@ -300,7 +300,7 @@ def penalty_string(distance, limit=None):
         return ui.colorize("changed", penalty_string)
 
 
-class ChangeRepresentation(object):
+class ChangeRepresentation:
     """Keeps track of all information needed to generate a (colored) text
     representation of the changes that will be made if an album or singleton's
     tags are changed according to `match`, which must be an AlbumMatch or
@@ -654,7 +654,7 @@ class AlbumChange(ChangeRepresentation):
     """Album change representation, setting cur_album"""
 
     def __init__(self, cur_artist, cur_album, match):
-        super(AlbumChange, self).__init__()
+        super().__init__()
         self.cur_artist = cur_artist
         self.cur_album = cur_album
         self.match = match
@@ -722,7 +722,7 @@ class TrackChange(ChangeRepresentation):
     """Track change representation, comparing item with match."""
 
     def __init__(self, cur_artist, cur_title, match):
-        super(TrackChange, self).__init__()
+        super().__init__()
         self.cur_artist = cur_artist
         self.cur_title = cur_title
         self.match = match

beets/util/__init__.py

@@ -16,7 +16,6 @@
 
 import errno
 import fnmatch
-import functools
 import os
 import platform
 import re
@@ -1106,26 +1105,3 @@ def par_map(transform: Callable, items: Iterable):
     pool.map(transform, items)
     pool.close()
     pool.join()
-
-
-def lazy_property(func: Callable) -> Callable:
-    """A decorator that creates a lazily evaluated property. On first access,
-    the property is assigned the return value of `func`. This first value is
-    stored, so that future accesses do not have to evaluate `func` again.
-
-    This behaviour is useful when `func` is expensive to evaluate, and it is
-    not certain that the result will be needed.
-    """
-    field_name = "_" + func.__name__
-
-    @property
-    @functools.wraps(func)
-    def wrapper(self):
-        if hasattr(self, field_name):
-            return getattr(self, field_name)
-
-        value = func(self)
-        setattr(self, field_name, value)
-        return value
-
-    return wrapper

beets/util/artresizer.py

@@ -449,7 +449,7 @@ def deinterlace(self, path_in, path_out=None):
             im = Image.open(syspath(path_in))
             im.save(py3_path(path_out), progressive=False)
             return path_out
-        except IOError:
+        except OSError:
             # FIXME: Should probably issue a warning?
             return path_in
 

beets/util/functemplate.py

@@ -31,7 +31,6 @@
 import dis
 import functools
 import re
-import sys
 import types
 
 SYMBOL_DELIM = "$"
@@ -97,8 +96,7 @@ def compile_func(arg_names, statements, name="_the_func", debug=False):
         "kw_defaults": [],
         "defaults": [ex_literal(None) for _ in arg_names],
     }
-    if "posonlyargs" in ast.arguments._fields:  # Added in Python 3.8.
-        args_fields["posonlyargs"] = []
+    args_fields["posonlyargs"] = []
     args = ast.arguments(**args_fields)
 
     func_def = ast.FunctionDef(
@@ -110,10 +108,7 @@ def compile_func(arg_names, statements, name="_the_func", debug=False):
 
     # The ast.Module signature changed in 3.8 to accept a list of types to
     # ignore.
-    if sys.version_info >= (3, 8):
-        mod = ast.Module([func_def], [])
-    else:
-        mod = ast.Module([func_def])
+    mod = ast.Module([func_def], [])
 
     ast.fix_missing_locations(mod)
 

beetsplug/discogs.py

@@ -87,7 +87,7 @@ def check_discogs_client(self):
         ]
         if True not in gt_min:
             self._log.warning(
-                ("python3-discogs-client version should be " ">= 2.3.15")
+                "python3-discogs-client version should be >= 2.3.15"
             )
 
     def setup(self, session=None):

beetsplug/substitute.py

@@ -46,7 +46,7 @@ def __init__(self):
         Get the configuration, register template function and create list of
         substitute rules.
         """
-        super(Substitute, self).__init__()
+        super().__init__()
         self.substitute_rules = []
         self.template_funcs["substitute"] = self.tmpl_substitute
 

docs/changelog.rst

@@ -10,6 +10,10 @@ Bug fixes:
 
 * Improved naming of temporary files by separating the random part with the file extension.
 
+For packagers:
+
+* The minimum Python version is now 3.8.
+
 2.0.0 (May 30, 2024)
 --------------------
 

docs/dev/plugins.rst

@@ -114,7 +114,7 @@ an example::
 
     class SomePlugin(BeetsPlugin):
       def __init__(self):
-        super(SomePlugin, self).__init__()
+        super().__init__()
         self.register_listener('pluginload', loaded)
 
 Note that if you want to access an attribute of your plugin (e.g. ``config`` or
@@ -125,7 +125,7 @@ registration process in this case::
 
     class SomePlugin(BeetsPlugin):
       def __init__(self):
-        super(SomePlugin, self).__init__()
+        super().__init__()
         self.register_listener('pluginload', self.loaded)
 
       def loaded(self):
@@ -354,7 +354,7 @@ Here's an example::
 
     class MyPlugin(BeetsPlugin):
         def __init__(self):
-            super(MyPlugin, self).__init__()
+            super().__init__()
             self.template_funcs['initial'] = _tmpl_initial
 
     def _tmpl_initial(text):
@@ -374,7 +374,7 @@ Here's an example that adds a ``$disc_and_track`` field::
 
     class MyPlugin(BeetsPlugin):
         def __init__(self):
-            super(MyPlugin, self).__init__()
+            super().__init__()
             self.template_fields['disc_and_track'] = _tmpl_disc_and_track
 
     def _tmpl_disc_and_track(item):
@@ -452,7 +452,7 @@ to register it::
     from beets.plugins import BeetsPlugin
     class ExamplePlugin(BeetsPlugin):
         def __init__(self):
-            super(ExamplePlugin, self).__init__()
+            super().__init__()
             self.import_stages = [self.stage]
         def stage(self, session, task):
             print('Importing something!')
@@ -596,7 +596,7 @@ plugin shall expose to the user::
 
     class ExamplePlugin(BeetsPlugin):
         def __init__(self):
-            super(ExamplePlugin, self).__init__()
+            super().__init__()
             self.register_listener('before_choose_candidate',
                                    self.before_choose_candidate_event)