setuptools v84.0.0

Features

• Newline-separated keywords and platforms, which are invalid and corrupt the generated metadata (pypa/setuptools#4887), are now handled forgivingly: each line is treated as a separate item and a deprecation warning is emitted. Newlines were never a valid separator for these fields -- the old specification <https://peps.python.org/pep-0345/>_ separated items with spaces and the current one uses commas. (#4887)
• Extension is now a dataclass, exposing type annotations for its constructor arguments so subclasses (e.g. in Setuptools) can inherit them without redeclaring each parameter. Passing unknown keyword arguments is now deprecated. (pypa/distutils#373) (#5022)
• The C compiler modules now emit log messages through their own compilers.C.* loggers instead of the distutils root logger, part of decoupling the compilers package from distutils. The logger names are normalized to a stable compilers.C.* prefix so they remain constant as the package migrates toward a standalone compilers.C distribution. (#5266)
• The C compilers gained a Compiler.call method -- a thin wrapper over subprocess.check_call (with macOS deployment-target env injection) that is the modern replacement for Compiler.spawn. The compilers no longer depend on distutils.spawn, distutils.dir_util, distutils.file_util, distutils._modified, or distutils.util.execute/split_quoted: the generic newer/newer_group and split_quoted helpers are vendored into the compilers package, and Compiler.mkpath/move_file/execute are implemented directly on the standard library (os.makedirs/shutil.move). The methods are retained for backward compatibility. (#5267)
• The compilers no longer depend on distutils.util, distutils.version, distutils.compat, or distutils._macos_compat. The platform-identification helpers (get_platform/get_host_platform/is_mingw) now live in distutils.compilers.platform.detect and the macOS deployment-target logic and compiler_fixup in distutils.compilers.platform.macos; CygwinCCompiler.gcc_version returns a packaging.version.Version. distutils.util re-exports the platform/macOS helpers from their new homes for backward compatibility rather than keeping duplicate copies. (sysconfig lookups still route through distutils pending its own decoupling.) (#5268)
• The compilers now read their build configuration from the standard library's sysconfig instead of distutils.sysconfig. Per-compiler customization -- previously distutils.sysconfig.customize_compiler -- has moved into Compiler.configure_system(): a no-op on the base class, with UnixCCompiler applying the compiler/flag/archiver settings CPython recorded in sysconfig (and the usual CC/CFLAGS/LDSHARED/… environment overrides). distutils.sysconfig.customize_compiler is retained as a thin wrapper that calls compiler.configure_system(). (#5269)

Bugfixes

• The MSVC linker now passes its arguments through a response file when the command line would exceed the Windows maximum length, fixing failures when linking a large number of objects. (#4177)
• The Cygwin and MinGW compilers now pass -O1 instead of a bare -O. The two are equivalent to GCC, but cc1 rejected the bare form when building 32-bit extensions with -m32. -- by :user:dchaudhari7177 (#4873)
• copy_file now preserves the full precision of the source's modification time, so a copy is no longer considered older than its source on filesystems with sub-second timestamp resolution. (pypa/distutils#379) (#5079)
• Setuptools wheels no longer bundled the project's own test modules. -- by :user:itscloud0 (#5212)
• build_ext no longer fails when cross-compiling with a compiler other than MSVC (such as MinGW). Compiler now provides a no-op initialize() that non-MSVC compilers inherit. (pypa/distutils#399)

Improved Documentation

• Clarified what "correspond exactly to the directory structure" means in the packages section of the Package Discovery user guide. (#4109)
• Documented how bdist_wheel's py_limited_api option controls abi3 wheel tagging for extension modules -- by :user:Himanshuagrawal4 (#4741)

Deprecations and Removals

• Compiler.spawn is deprecated in favor of the new Compiler.call. call raises native subprocess exceptions; spawn remains as a shim that emits a DeprecationWarning and translates them to DistutilsExecError. The MSVC spawn compatibility shim for third-party monkeypatches predating the env argument (numpy.distutils before 1.19, per pypa/distutils#15) has been removed. distutils.spawn.spawn is likewise reduced to a thin wrapper around subprocess.check_call: it no longer resolves cmd[0] via shutil.which (subprocess searches PATH itself) nor injects MACOSX_DEPLOYMENT_TARGET (that now lives with the compilers, the only callers to which it applied). (#5267)
• Building an extension with a MACOSX_DEPLOYMENT_TARGET lower than the interpreter's configured value now raises compilers.errors.PlatformError instead of distutils.errors.DistutilsPlatformError (the macOS deployment-target check moved into the compilers package). CygwinCCompiler.gcc_version returns a packaging.version.Version rather than the removed distutils.version.LooseVersion. Completing the transition begun in pypa/distutils#246, UnixCCompiler.runtime_library_dir_option now returns the ["-Wl,--enable-new-dtags", "-Wl,-rpath,<dir>"] list directly for GNU ld rather than collapsing it into a single string, and the temporary distutils.compat.consolidate_linker_args shim has been removed. (#5268)
• The compilers now define their own exception vocabulary instead of borrowing distutils' framework errors. Language-agnostic exceptions (Error, UnknownFileType, and a new PlatformError) live at distutils.compilers.errors, leaving room for future compilers.<language> siblings; the C/C++-specific CompileError/LinkError/LibError/PreprocessError remain in distutils.compilers.C.errors. The compilers now raise compilers.errors.PlatformError where they previously raised distutils.errors.DistutilsPlatformError/DistutilsModuleError, and compilers._modified.newer raises the stdlib FileNotFoundError. distutils.errors keeps its own framework exceptions and re-exports the compiler ones (CCompilerError, CompileError, etc.) for backward compatibility; because CCompilerError is compilers.errors.Error, code catching it (as distutils' top-level handlers do) still catches the new PlatformError. (#5270)
• customize_compiler now asserts that the compiler-related config variables (CC, CXX, CFLAGS, etc.) resolve to strings, raising AssertionError if any are unexpectedly None rather than failing later with a less clear error. (pypa/distutils#363)