refactor: pull arch out into separate file

cibuildwheel/architecture.py

@@ -0,0 +1,86 @@
+import functools
+import platform as platform_module
+import re
+from enum import Enum
+from typing import Set
+
+from .typing import PlatformName, assert_never
+
+PRETTY_NAMES = {'linux': 'Linux', 'macos': 'macOS', 'windows': 'Windows'}
+
+
+@functools.total_ordering
+class Architecture(Enum):
+    value: str
+
+    # mac/linux archs
+    x86_64 = 'x86_64'
+    i686 = 'i686'
+    aarch64 = 'aarch64'
+    ppc64le = 'ppc64le'
+    s390x = 's390x'
+
+    # windows archs
+    x86 = 'x86'
+    AMD64 = 'AMD64'
+
+    # Allow this to be sorted
+    def __lt__(self, other: "Architecture") -> bool:
+        return self.value < other.value
+
+    @staticmethod
+    def parse_config(config: str, platform: PlatformName) -> 'Set[Architecture]':
+        result = set()
+        for arch_str in re.split(r'[\s,]+', config):
+            if arch_str == 'auto':
+                result |= Architecture.auto_archs(platform=platform)
+            elif arch_str == 'native':
+                result.add(Architecture(platform_module.machine()))
+            elif arch_str == 'all':
+                result |= Architecture.all_archs(platform=platform)
+            else:
+                result.add(Architecture(arch_str))
+        return result
+
+    @staticmethod
+    def auto_archs(platform: PlatformName) -> 'Set[Architecture]':
+        native_architecture = Architecture(platform_module.machine())
+        result = {native_architecture}
+        if platform == 'linux' and native_architecture == Architecture.x86_64:
+            # x86_64 machines can run i686 docker containers
+            result.add(Architecture.i686)
+        if platform == 'windows' and native_architecture == Architecture.AMD64:
+            result.add(Architecture.x86)
+        return result
+
+    @staticmethod
+    def all_archs(platform: PlatformName) -> 'Set[Architecture]':
+        if platform == 'linux':
+            return {Architecture.x86_64, Architecture.i686, Architecture.aarch64, Architecture.ppc64le, Architecture.s390x}
+        elif platform == 'macos':
+            return {Architecture.x86_64}
+        elif platform == 'windows':
+            return {Architecture.x86, Architecture.AMD64}
+        else:
+            assert_never(platform)
+
+
+def allowed_architectures_check(
+    platform: PlatformName,
+    architectures: Set[Architecture],
+) -> None:
+
+    allowed_architectures = Architecture.all_archs(platform)
+
+    msg = f'{PRETTY_NAMES[platform]} only supports {sorted(allowed_architectures)} at the moment.'
+
+    if platform != 'linux':
+        msg += ' If you want to set emulation architectures on Linux, use CIBW_ARCHS_LINUX instead.'
+
+    if not architectures <= allowed_architectures:
+        msg = f'Invalid archs option {architectures}. ' + msg
+        raise ValueError(msg)
+
+    if not architectures:
+        msg = 'Empty archs option set. ' + msg
+        raise ValueError(msg)