Drop Python 3.6 support (msgpack#543)

The following steps have been taken:

1. Black was updated to latest version. The code has been formatted with
the new version.
2. The pyupgrade utility is installed. This helped to remove all the
code that was needed to support Python < 3.7.

Fix msgpack#541.

Co-authored-by: Inada Naoki <songofacandy@gmail.com>

Author: evgenymarkov

Makefile

@@ -1,10 +1,16 @@
+PYTHON_SOURCES = msgpack test setup.py
+
 .PHONY: all
 all: cython
 	python setup.py build_ext -i -f
 
 .PHONY: black
 black:
-	black -S msgpack/ test/ setup.py
+	black $(PYTHON_SOURCES)
+
+.PHONY: pyupgrade
+pyupgrade:
+	@find $(PYTHON_SOURCES) -name '*.py' -type f -exec pyupgrade --py37-plus '{}' \;
 
 .PHONY: cython
 cython:

msgpack/__init__.py

@@ -1,4 +1,3 @@
-# coding: utf-8
 from .exceptions import *
 from .ext import ExtType, Timestamp
 

msgpack/ext.py

@@ -1,4 +1,3 @@
-# coding: utf-8
 from collections import namedtuple
 import datetime
 import sys
@@ -15,10 +14,10 @@ def __new__(cls, code, data):
             raise TypeError("data must be bytes")
         if not 0 <= code <= 127:
             raise ValueError("code must be 0~127")
-        return super(ExtType, cls).__new__(cls, code, data)
+        return super().__new__(cls, code, data)
 
 
-class Timestamp(object):
+class Timestamp:
     """Timestamp represents the Timestamp extension type in msgpack.
 
     When built with Cython, msgpack uses C methods to pack and unpack `Timestamp`. When using pure-Python
@@ -47,24 +46,18 @@ def __init__(self, seconds, nanoseconds=0):
         if not isinstance(nanoseconds, int):
             raise TypeError("nanoseconds must be an integer")
         if not (0 <= nanoseconds < 10**9):
-            raise ValueError(
-                "nanoseconds must be a non-negative integer less than 999999999."
-            )
+            raise ValueError("nanoseconds must be a non-negative integer less than 999999999.")
         self.seconds = seconds
         self.nanoseconds = nanoseconds
 
     def __repr__(self):
         """String representation of Timestamp."""
-        return "Timestamp(seconds={0}, nanoseconds={1})".format(
-            self.seconds, self.nanoseconds
-        )
+        return f"Timestamp(seconds={self.seconds}, nanoseconds={self.nanoseconds})"
 
     def __eq__(self, other):
         """Check for equality with another Timestamp object"""
         if type(other) is self.__class__:
-            return (
-                self.seconds == other.seconds and self.nanoseconds == other.nanoseconds
-            )
+            return self.seconds == other.seconds and self.nanoseconds == other.nanoseconds
         return False
 
     def __ne__(self, other):
@@ -164,9 +157,7 @@ def to_datetime(self):
         :rtype: datetime.
         """
         utc = datetime.timezone.utc
-        return datetime.datetime.fromtimestamp(0, utc) + datetime.timedelta(
-            seconds=self.to_unix()
-        )
+        return datetime.datetime.fromtimestamp(0, utc) + datetime.timedelta(seconds=self.to_unix())
 
     @staticmethod
     def from_datetime(dt):

msgpack/fallback.py

@@ -4,23 +4,6 @@
 import struct
 
 
-if sys.version_info < (3, 5):
-    # Ugly hack...
-    RecursionError = RuntimeError
-
-    def _is_recursionerror(e):
-        return (
-            len(e.args) == 1
-            and isinstance(e.args[0], str)
-            and e.args[0].startswith("maximum recursion depth exceeded")
-        )
-
-else:
-
-    def _is_recursionerror(e):
-        return True
-
-
 if hasattr(sys, "pypy_version_info"):
     # StringIO is slow on PyPy, StringIO is faster.  However: PyPy's own
     # StringBuilder is fastest.
@@ -32,7 +15,7 @@ def _is_recursionerror(e):
         from __pypy__.builders import StringBuilder
     USING_STRINGBUILDER = True
 
-    class StringIO(object):
+    class StringIO:
         def __init__(self, s=b""):
             if s:
                 self.builder = StringBuilder(len(s))
@@ -109,10 +92,8 @@ def unpackb(packed, **kwargs):
         ret = unpacker._unpack()
     except OutOfData:
         raise ValueError("Unpack failed: incomplete input")
-    except RecursionError as e:
-        if _is_recursionerror(e):
-            raise StackError
-        raise
+    except RecursionError:
+        raise StackError
     if unpacker._got_extradata():
         raise ExtraData(ret, unpacker._get_extradata())
     return ret
@@ -151,7 +132,7 @@ def unpackb(packed, **kwargs):
 }
 
 
-class Unpacker(object):
+class Unpacker:
     """Streaming unpacker.
 
     Arguments:
@@ -334,9 +315,7 @@ def __init__(
         if object_pairs_hook is not None and not callable(object_pairs_hook):
             raise TypeError("`object_pairs_hook` is not callable")
         if object_hook is not None and object_pairs_hook is not None:
-            raise TypeError(
-                "object_pairs_hook and object_hook are mutually " "exclusive"
-            )
+            raise TypeError("object_pairs_hook and object_hook are mutually exclusive")
         if not callable(ext_hook):
             raise TypeError("`ext_hook` is not callable")
 
@@ -428,20 +407,18 @@ def _read_header(self):
             n = b & 0b00011111
             typ = TYPE_RAW
             if n > self._max_str_len:
-                raise ValueError("%s exceeds max_str_len(%s)" % (n, self._max_str_len))
+                raise ValueError(f"{n} exceeds max_str_len({self._max_str_len})")
             obj = self._read(n)
         elif b & 0b11110000 == 0b10010000:
             n = b & 0b00001111
             typ = TYPE_ARRAY
             if n > self._max_array_len:
-                raise ValueError(
-                    "%s exceeds max_array_len(%s)" % (n, self._max_array_len)
-                )
+                raise ValueError(f"{n} exceeds max_array_len({self._max_array_len})")
         elif b & 0b11110000 == 0b10000000:
             n = b & 0b00001111
             typ = TYPE_MAP
             if n > self._max_map_len:
-                raise ValueError("%s exceeds max_map_len(%s)" % (n, self._max_map_len))
+                raise ValueError(f"{n} exceeds max_map_len({self._max_map_len})")
         elif b == 0xC0:
             obj = None
         elif b == 0xC2:
@@ -457,15 +434,15 @@ def _read_header(self):
                 n = self._buffer[self._buff_i]
             self._buff_i += size
             if n > self._max_bin_len:
-                raise ValueError("%s exceeds max_bin_len(%s)" % (n, self._max_bin_len))
+                raise ValueError(f"{n} exceeds max_bin_len({self._max_bin_len})")
             obj = self._read(n)
         elif 0xC7 <= b <= 0xC9:
             size, fmt, typ = _MSGPACK_HEADERS[b]
             self._reserve(size)
             L, n = struct.unpack_from(fmt, self._buffer, self._buff_i)
             self._buff_i += size
             if L > self._max_ext_len:
-                raise ValueError("%s exceeds max_ext_len(%s)" % (L, self._max_ext_len))
+                raise ValueError(f"{L} exceeds max_ext_len({self._max_ext_len})")
             obj = self._read(L)
         elif 0xCA <= b <= 0xD3:
             size, fmt = _MSGPACK_HEADERS[b]
@@ -478,9 +455,7 @@ def _read_header(self):
         elif 0xD4 <= b <= 0xD8:
             size, fmt, typ = _MSGPACK_HEADERS[b]
             if self._max_ext_len < size:
-                raise ValueError(
-                    "%s exceeds max_ext_len(%s)" % (size, self._max_ext_len)
-                )
+                raise ValueError(f"{size} exceeds max_ext_len({self._max_ext_len})")
             self._reserve(size + 1)
             n, obj = struct.unpack_from(fmt, self._buffer, self._buff_i)
             self._buff_i += size + 1
@@ -493,24 +468,22 @@ def _read_header(self):
                 n = self._buffer[self._buff_i]
             self._buff_i += size
             if n > self._max_str_len:
-                raise ValueError("%s exceeds max_str_len(%s)" % (n, self._max_str_len))
+                raise ValueError(f"{n} exceeds max_str_len({self._max_str_len})")
             obj = self._read(n)
         elif 0xDC <= b <= 0xDD:
             size, fmt, typ = _MSGPACK_HEADERS[b]
             self._reserve(size)
             (n,) = struct.unpack_from(fmt, self._buffer, self._buff_i)
             self._buff_i += size
             if n > self._max_array_len:
-                raise ValueError(
-                    "%s exceeds max_array_len(%s)" % (n, self._max_array_len)
-                )
+                raise ValueError(f"{n} exceeds max_array_len({self._max_array_len})")
         elif 0xDE <= b <= 0xDF:
             size, fmt, typ = _MSGPACK_HEADERS[b]
             self._reserve(size)
             (n,) = struct.unpack_from(fmt, self._buffer, self._buff_i)
             self._buff_i += size
             if n > self._max_map_len:
-                raise ValueError("%s exceeds max_map_len(%s)" % (n, self._max_map_len))
+                raise ValueError(f"{n} exceeds max_map_len({self._max_map_len})")
         else:
             raise FormatError("Unknown header: 0x%x" % b)
         return typ, n, obj
@@ -549,17 +522,14 @@ def _unpack(self, execute=EX_CONSTRUCT):
                 return
             if self._object_pairs_hook is not None:
                 ret = self._object_pairs_hook(
-                    (self._unpack(EX_CONSTRUCT), self._unpack(EX_CONSTRUCT))
-                    for _ in range(n)
+                    (self._unpack(EX_CONSTRUCT), self._unpack(EX_CONSTRUCT)) for _ in range(n)
                 )
             else:
                 ret = {}
                 for _ in range(n):
                     key = self._unpack(EX_CONSTRUCT)
                     if self._strict_map_key and type(key) not in (str, bytes):
-                        raise ValueError(
-                            "%s is not allowed for map key" % str(type(key))
-                        )
+                        raise ValueError("%s is not allowed for map key" % str(type(key)))
                     if type(key) is str:
                         key = sys.intern(key)
                     ret[key] = self._unpack(EX_CONSTRUCT)
@@ -634,7 +604,7 @@ def tell(self):
         return self._stream_offset
 
 
-class Packer(object):
+class Packer:
     """
     MessagePack Packer
 
@@ -844,9 +814,9 @@ def _pack(
                 continue
 
             if self._datetime and check(obj, _DateTime):
-                raise ValueError("Cannot serialize %r where tzinfo=None" % (obj,))
+                raise ValueError(f"Cannot serialize {obj!r} where tzinfo=None")
 
-            raise TypeError("Cannot serialize %r" % (obj,))
+            raise TypeError(f"Cannot serialize {obj!r}")
 
     def pack(self, obj):
         try:
@@ -933,7 +903,7 @@ def _pack_map_header(self, n):
 
     def _pack_map_pairs(self, n, pairs, nest_limit=DEFAULT_RECURSE_LIMIT):
         self._pack_map_header(n)
-        for (k, v) in pairs:
+        for k, v in pairs:
             self._pack(k, nest_limit - 1)
             self._pack(v, nest_limit - 1)
 

pyproject.toml

@@ -6,3 +6,8 @@ requires = [
     "setuptools >= 35.0.2",
 ]
 build-backend = "setuptools.build_meta"
+
+[tool.black]
+line-length = 100
+target-version = ["py37"]
+skip_string_normalization = true

requirements.txt

@@ -1,5 +1,7 @@
-# Also declared in pyproject.toml, if updating here please also update there
+# Also declared in pyproject.toml, if updating here please also update there.
 Cython~=0.29.30
 
-# dev only tools. no need to add pyproject
-black==22.3.0
+# Tools required only for development. No need to add it to pyproject.toml file.
+black==23.3.0
+pytest==7.3.1
+pyupgrade==3.3.2

setup.cfg

@@ -17,7 +17,6 @@ project_urls =
 
 classifiers =
     Programming Language :: Python :: 3
-    Programming Language :: Python :: 3.6
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9

setup.py

@@ -1,5 +1,4 @@
 #!/usr/bin/env python
-# coding: utf-8
 import io
 import os
 import sys
@@ -25,7 +24,7 @@ class NoCython(Exception):
 
 
 def cythonize(src):
-    sys.stderr.write("cythonize: %r\n" % (src,))
+    sys.stderr.write(f"cythonize: {src!r}\n")
     cython_compiler.compile([src], cplus=True)
 
 
@@ -36,11 +35,7 @@ def ensure_source(src):
         if not have_cython:
             raise NoCython
         cythonize(pyx)
-    elif (
-        os.path.exists(pyx)
-        and os.stat(src).st_mtime < os.stat(pyx).st_mtime
-        and have_cython
-    ):
+    elif os.path.exists(pyx) and os.stat(src).st_mtime < os.stat(pyx).st_mtime and have_cython:
         cythonize(pyx)
     return src
 

test/test_buffer.py

@@ -1,5 +1,4 @@
 #!/usr/bin/env python
-# coding: utf-8
 
 import sys
 import pytest

test/test_case.py

@@ -1,11 +1,10 @@
 #!/usr/bin/env python
-# coding: utf-8
 from msgpack import packb, unpackb
 
 
 def check(length, obj, use_bin_type=True):
     v = packb(obj, use_bin_type=use_bin_type)
-    assert len(v) == length, "%r length should be %r but get %r" % (obj, length, len(v))
+    assert len(v) == length, f"{obj!r} length should be {length!r} but get {len(v)!r}"
     assert unpackb(v, use_list=0, raw=not use_bin_type) == obj
 
 
@@ -120,11 +119,11 @@ def test_match():
         ),
         ({}, b"\x80"),
         (
-            dict([(x, x) for x in range(15)]),
+            {x: x for x in range(15)},
             b"\x8f\x00\x00\x01\x01\x02\x02\x03\x03\x04\x04\x05\x05\x06\x06\x07\x07\x08\x08\t\t\n\n\x0b\x0b\x0c\x0c\r\r\x0e\x0e",
         ),
         (
-            dict([(x, x) for x in range(16)]),
+            {x: x for x in range(16)},
             b"\xde\x00\x10\x00\x00\x01\x01\x02\x02\x03\x03\x04\x04\x05\x05\x06\x06\x07\x07\x08\x08\t\t\n\n\x0b\x0b\x0c\x0c\r\r\x0e\x0e\x0f\x0f",
         ),
     ]