Drop support for running with Python 3.8 (#17492)

Similar to last year (#15566), start by dropping support for running
mypy with Python 3.8.
Users will still be able to type check 3.8 code with `--python-version
3.8` until typeshed drops the support for it.

It's a bit early as the EOL for Python 3.8 is in ~3 months. However,
since the branch for `1.11.0` has been cut already, we'd only drop the
support with `1.12.0` which isn't due for another 1-2 months.
Additionally dropping `3.8` now will make it easier to support `3.13`
with its C-API changes and also give us enough time to cleanup the
remaining 3.8 code blocks and documentation references.

---------

Co-authored-by: Ali Hamdan <[email protected]>

Author: cdce8p

.github/workflows/test.yml

@@ -31,24 +31,18 @@ jobs:
         include:
         # Make sure to run mypyc compiled unit tests for both
         # the oldest and newest supported Python versions
-        - name: Test suite with py38-ubuntu, mypyc-compiled
-          python: '3.8'
+        - name: Test suite with py39-ubuntu, mypyc-compiled
+          python: '3.9'
           arch: x64
           os: ubuntu-latest
           toxenv: py
           tox_extra_args: "-n 4"
           test_mypyc: true
-        - name: Test suite with py38-windows-64
-          python: '3.8'
-          arch: x64
-          os: windows-latest
-          toxenv: py38
-          tox_extra_args: "-n 4"
-        - name: Test suite with py39-ubuntu
+        - name: Test suite with py39-windows-64
           python: '3.9'
           arch: x64
-          os: ubuntu-latest
-          toxenv: py
+          os: windows-latest
+          toxenv: py39
           tox_extra_args: "-n 4"
         - name: Test suite with py310-ubuntu
           python: '3.10'
@@ -88,7 +82,7 @@ jobs:
         #   test_mypyc: true
 
         - name: mypyc runtime tests with py39-macos
-          python: '3.9.18'
+          python: '3.9.21'
           arch: x64
           # TODO: macos-13 is the last one to support Python 3.9, change it to macos-latest when updating the Python version
           os: macos-13
@@ -98,20 +92,20 @@ jobs:
         # - https://github.com/python/mypy/issues/17819
         # - https://github.com/python/mypy/pull/17822
         # - name: mypyc runtime tests with py38-debug-build-ubuntu
-        #   python: '3.8.17'
+        #   python: '3.9.21'
         #   arch: x64
         #   os: ubuntu-latest
         #   toxenv: py
         #   tox_extra_args: "-n 4 mypyc/test/test_run.py mypyc/test/test_external.py"
         #   debug_build: true
 
-        - name: Type check our own code (py38-ubuntu)
-          python: '3.8'
+        - name: Type check our own code (py39-ubuntu)
+          python: '3.9'
           arch: x64
           os: ubuntu-latest
           toxenv: type
-        - name: Type check our own code (py38-windows-64)
-          python: '3.8'
+        - name: Type check our own code (py39-windows-64)
+          python: '3.9'
           arch: x64
           os: windows-latest
           toxenv: type

.github/workflows/test_stubgenc.yml

@@ -30,10 +30,10 @@ jobs:
 
     - uses: actions/checkout@v4
 
-    - name: Setup 🐍 3.8
+    - name: Setup 🐍 3.9
       uses: actions/setup-python@v5
       with:
-        python-version: 3.8
+        python-version: 3.9
 
     - name: Test stubgenc
       run: misc/test-stubgenc.sh

CONTRIBUTING.md

@@ -51,7 +51,7 @@ hash -r  # This resets shell PATH cache, not necessary on Windows
 ```
 
 > **Note**
-> You'll need Python 3.8 or higher to install all requirements listed in
+> You'll need Python 3.9 or higher to install all requirements listed in
 > test-requirements.txt
 
 ### Running tests

docs/source/getting_started.rst

@@ -16,7 +16,7 @@ may not make much sense otherwise.
 Installing and running mypy
 ***************************
 
-Mypy requires Python 3.8 or later to run.  You can install mypy using pip:
+Mypy requires Python 3.9 or later to run.  You can install mypy using pip:
 
 .. code-block:: shell
 

mypy/defaults.py

@@ -6,7 +6,7 @@
 # Earliest fully supported Python 3.x version. Used as the default Python
 # version in tests. Mypy wheels should be built starting with this version,
 # and CI tests should be run on this version (and later versions).
-PYTHON3_VERSION: Final = (3, 8)
+PYTHON3_VERSION: Final = (3, 9)
 
 # Earliest Python 3.x version supported via --python-version 3.x. To run
 # mypy, at least version PYTHON3_VERSION is needed.

mypy/test/meta/test_parse_data.py

@@ -50,13 +50,13 @@ def test_bad_ge_version_check(self) -> None:
             """
             [case abc]
             s: str
-            [out version>=3.8]
+            [out version>=3.9]
             abc
             """
         )
 
         # Assert
-        assert "version>=3.8 always true since minimum runtime version is (3, 8)" in actual.stdout
+        assert "version>=3.9 always true since minimum runtime version is (3, 9)" in actual.stdout
 
     def test_bad_eq_version_check(self) -> None:
         # Act
@@ -70,4 +70,4 @@ def test_bad_eq_version_check(self) -> None:
         )
 
         # Assert
-        assert "version==3.7 always false since minimum runtime version is (3, 8)" in actual.stdout
+        assert "version==3.7 always false since minimum runtime version is (3, 9)" in actual.stdout

mypy/util.py

@@ -490,10 +490,10 @@ def get_unique_redefinition_name(name: str, existing: Container[str]) -> str:
 def check_python_version(program: str) -> None:
     """Report issues with the Python used to run mypy, dmypy, or stubgen"""
     # Check for known bad Python versions.
-    if sys.version_info[:2] < (3, 8):  # noqa: UP036
+    if sys.version_info[:2] < (3, 9):
         sys.exit(
-            "Running {name} with Python 3.7 or lower is not supported; "
-            "please upgrade to 3.8 or newer".format(name=program)
+            "Running {name} with Python 3.8 or lower is not supported; "
+            "please upgrade to 3.9 or newer".format(name=program)
         )
 
 

mypy_self_check.ini

@@ -6,7 +6,7 @@ show_traceback = True
 pretty = True
 always_false = MYPYC
 plugins = mypy.plugins.proper_plugin
-python_version = 3.8
+python_version = 3.9
 exclude = mypy/typeshed/|mypyc/test-data/|mypyc/lib-rt/
 enable_error_code = ignore-without-code,redundant-expr
 enable_incomplete_feature = PreciseTupleTypes

mypyc/doc/getting_started.rst

@@ -38,7 +38,7 @@ Installation
 ------------
 
 Mypyc is shipped as part of the mypy distribution. Install mypy like
-this (you need Python 3.8 or later):
+this (you need Python 3.9 or later):
 
 .. code-block::
 

mypyc/test/test_run.py

@@ -320,6 +320,7 @@ def run_case_step(self, testcase: DataDrivenTestCase, incremental_step: int) ->
             # TODO: testDecorators1 hangs on 3.12, remove this once fixed
             proc.wait(timeout=30)
         output = proc.communicate()[0].decode("utf8")
+        output = output.replace(f'  File "{os.getcwd()}{os.sep}', '  File "')
         outlines = output.splitlines()
 
         if testcase.config.getoption("--mypyc-showc"):

pyproject.toml

@@ -36,7 +36,6 @@ classifiers = [
   "Intended Audience :: Developers",
   "License :: OSI Approved :: MIT License",
   "Programming Language :: Python :: 3",
-  "Programming Language :: Python :: 3.8",
   "Programming Language :: Python :: 3.9",
   "Programming Language :: Python :: 3.10",
   "Programming Language :: Python :: 3.11",
@@ -45,7 +44,7 @@ classifiers = [
   "Topic :: Software Development",
   "Typing :: Typed",
 ]
-requires-python = ">=3.8"
+requires-python = ">=3.9"
 dependencies = [
   # When changing this, also update build-system.requires and mypy-requirements.txt
   "typing_extensions>=4.6.0",

setup.py

@@ -8,8 +8,8 @@
 import sys
 from typing import TYPE_CHECKING, Any
 
-if sys.version_info < (3, 8, 0):  # noqa: UP036
-    sys.stderr.write("ERROR: You need Python 3.8 or later to use mypy.\n")
+if sys.version_info < (3, 9, 0):
+    sys.stderr.write("ERROR: You need Python 3.9 or later to use mypy.\n")
     exit(1)
 
 # we'll import stuff from the source tree, let's ensure is on the sys path

test-data/unit/check-columns.test

@@ -260,7 +260,7 @@ class D(A):
                               # N:5:          def f(self) -> None
 
 [case testColumnMissingTypeParameters]
-# flags: --disallow-any-generics
+# flags: --python-version 3.8 --disallow-any-generics
 from typing import List, Callable
 def f(x: List) -> None: pass # E:10: Missing type parameters for generic type "List"
 def g(x: list) -> None: pass # E:10: Implicit generic "Any". Use "typing.List" and specify generic parameters

test-data/unit/check-errorcodes.test

@@ -328,7 +328,7 @@ a: A
 a.x = ''  # E: Incompatible types in assignment (expression has type "str", variable has type "int")  [assignment]
 
 [case testErrorCodeMissingTypeArg]
-# flags: --disallow-any-generics
+# flags: --python-version 3.8 --disallow-any-generics
 from typing import List, TypeVar
 x: List  # E: Missing type parameters for generic type "List"  [type-arg]
 y: list  # E: Implicit generic "Any". Use "typing.List" and specify generic parameters  [type-arg]

test-data/unit/check-functools.test

@@ -289,6 +289,7 @@ p1("a", "b")  # TODO: false negative
 [builtins fixtures/dict.pyi]
 
 [case testFunctoolsPartialTypeGuard]
+# flags: --python-version 3.8
 import functools
 from typing_extensions import TypeGuard
 

test-data/unit/check-generics.test

@@ -515,6 +515,7 @@ Alias[int]("a")  # E: Argument 1 to "Node" has incompatible type "str"; expected
 [out]
 
 [case testTypeApplicationCrash]
+# flags: --python-version 3.8
 import types
 type[int] # this was crashing, see #2302 (comment)  # E: The type "Type[type]" is not generic and not indexable
 [builtins fixtures/tuple.pyi]
@@ -1130,6 +1131,7 @@ reveal_type(Bad) # N: Revealed type is "Any"
 [out]
 
 [case testNoSubscriptionOfBuiltinAliases]
+# flags: --python-version 3.8
 from typing import List, TypeVar
 
 list[int]() # E: "list" is not subscriptable

test-data/unit/check-incremental.test

@@ -3753,7 +3753,7 @@ import b
 [file b.py]
 -- This is a heinous hack, but we simulate having a invalid cache by clobbering
 -- the proto deps file with something with mtime mismatches.
-[file ../.mypy_cache/3.8/@deps.meta.json.2]
+[file ../.mypy_cache/3.9/@deps.meta.json.2]
 {"snapshot": {"__main__": "a7c958b001a45bd6a2a320f4e53c4c16", "a": "d41d8cd98f00b204e9800998ecf8427e", "b": "d41d8cd98f00b204e9800998ecf8427e", "builtins": "c532c89da517a4b779bcf7a964478d67"}, "deps_meta": {"@root": {"path": "@root.deps.json", "mtime": 0}, "__main__": {"path": "__main__.deps.json", "mtime": 0}, "a": {"path": "a.deps.json", "mtime": 0}, "b": {"path": "b.deps.json", "mtime": 0}, "builtins": {"path": "builtins.deps.json", "mtime": 0}}}
 [file ../.mypy_cache/.gitignore]
 # Another hack to not trigger a .gitignore creation failure "false positive"
@@ -3788,7 +3788,7 @@ import b
 [file b.py]
 -- This is a heinous hack, but we simulate having a invalid cache by deleting
 -- the proto deps file.
-[delete ../.mypy_cache/3.8/@deps.meta.json.2]
+[delete ../.mypy_cache/3.9/@deps.meta.json.2]
 [file b.py.2]
 # uh
 -- Every file should get reloaded, since the cache was invalidated

test-data/unit/fine-grained-cache-incremental.test

@@ -202,7 +202,7 @@ a.py:8: note:     x: expected "int", got "str"
 [file b.py]
 -- This is a heinous hack, but we simulate having a invalid cache by clobbering
 -- the proto deps file with something with mtime mismatches.
-[file ../.mypy_cache/3.8/@deps.meta.json.2]
+[file ../.mypy_cache/3.9/@deps.meta.json.2]
 {"snapshot": {"__main__": "a7c958b001a45bd6a2a320f4e53c4c16", "a": "d41d8cd98f00b204e9800998ecf8427e", "b": "d41d8cd98f00b204e9800998ecf8427e", "builtins": "c532c89da517a4b779bcf7a964478d67"}, "deps_meta": {"@root": {"path": "@root.deps.json", "mtime": 0}, "__main__": {"path": "__main__.deps.json", "mtime": 0}, "a": {"path": "a.deps.json", "mtime": 0}, "b": {"path": "b.deps.json", "mtime": 0}, "builtins": {"path": "builtins.deps.json", "mtime": 0}}}
 
 [file b.py.2]
@@ -234,8 +234,8 @@ x = 10
 [file p/c.py]
 class C: pass
 
-[delete ../.mypy_cache/3.8/b.meta.json.2]
-[delete ../.mypy_cache/3.8/p/c.meta.json.2]
+[delete ../.mypy_cache/3.9/b.meta.json.2]
+[delete ../.mypy_cache/3.9/p/c.meta.json.2]
 
 [out]
 ==

test-data/unit/fine-grained.test

@@ -10228,7 +10228,7 @@ class Base(Protocol):
 main:5: error: Call to abstract method "meth" of "Base" with trivial body via super() is unsafe
 
 [case testPrettyMessageSorting]
-# flags: --pretty
+# flags: --python-version 3.8 --pretty
 import a
 
 [file a.py]

test-data/unit/parse-errors.test

@@ -55,7 +55,7 @@ file:1: error: invalid syntax
 [case testUnexpectedEof]
 if 1:
 [out]
-file:1: error: unexpected EOF while parsing
+file:1: error: expected an indented block
 
 [case testInvalidKeywordArguments1]
 f(x=y, z)
@@ -434,7 +434,7 @@ file:1: error: invalid syntax
 [case testSmartQuotes]
 foo = ‘bar’
 [out]
-file:1: error: invalid character in identifier
+file:1: error: invalid character '‘' (U+2018)
 
 [case testExceptCommaInPython3]
 try:

test-requirements.in

@@ -12,5 +12,5 @@ pytest>=8.1.0
 pytest-xdist>=1.34.0
 pytest-cov>=2.10.0
 setuptools>=75.1.0
-tomli>=1.1.0  # needed even on py311+ so the self check passes with --python-version 3.8
+tomli>=1.1.0  # needed even on py311+ so the self check passes with --python-version 3.9
 pre_commit>=3.5.0