fix: better cross-platform auto archs

This improves the default arch selection when targetting a different platform.

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

cibuildwheel/architecture.py

@@ -3,12 +3,25 @@ from __future__ import annotations
 import functools
 import platform as platform_module
 import re
+import sys
 from enum import Enum
 
 from .typing import Final, Literal, PlatformName, assert_never
 
 PRETTY_NAMES: Final = {"linux": "Linux", "macos": "macOS", "windows": "Windows"}
 
+ARCH_CATEGORIES: Final[dict[str, set[str]]] = {
+    "32": {"i686", "x86"},
+    "64": {"x86_64", "AMD64"},
+    "arm": {"ARM64", "aarch64", "arm64"},
+}
+
+PLATFORM_CATEGORIES: Final[dict[PlatformName, set[str]]] = {
+    "linux": {"i686", "x86_64", "aarch64", "ppc64le", "s390x"},
+    "macos": {"x86_64", "arm64", "universal2"},
+    "windows": {"x86", "AMD64", "ARM64"},
+}
+
 
 @functools.total_ordering
 class Architecture(Enum):
@@ -56,14 +69,34 @@ class Architecture(Enum):
 
     @staticmethod
     def auto_archs(platform: PlatformName) -> set[Architecture]:
-        native_architecture = Architecture(platform_module.machine())
-        result = {native_architecture}
+        native_machine = platform_module.machine()
 
-        if platform == "linux" and native_architecture == Architecture.x86_64:
+        # Cross-platform support. Used for --print-build-identifiers or docker builds.
+        host_platform = (
+            "windows"
+            if sys.platform.startswith("win")
+            else ("macos" if sys.platform.startswith("darwin") else "linux")
+        )
+
+        result = set()
+
+        # Replace native_machine with the matching machine for intel or arm
+        if host_platform == platform:
+            native_architecture = Architecture(native_machine)
+            result.add(native_architecture)
+        else:
+            for arch_group in ARCH_CATEGORIES.values():
+                if native_machine in arch_group:
+                    possible_archs = arch_group & PLATFORM_CATEGORIES[platform]
+                    if len(possible_archs) == 1:
+                        (cross_machine,) = possible_archs
+                        result.add(Architecture(cross_machine))
+
+        if platform == "linux" and Architecture.x86_64 in result:
             # x86_64 machines can run i686 containers
             result.add(Architecture.i686)
 
-        if platform == "windows" and native_architecture == Architecture.AMD64:
+        if platform == "windows" and Architecture.AMD64 in result:
             result.add(Architecture.x86)
 
         return result
@@ -71,21 +104,15 @@ class Architecture(Enum):
     @staticmethod
     def all_archs(platform: PlatformName) -> set[Architecture]:
         all_archs_map = {
-            "linux": {
-                Architecture.x86_64,
-                Architecture.i686,
-                Architecture.aarch64,
-                Architecture.ppc64le,
-                Architecture.s390x,
-            },
-            "macos": {Architecture.x86_64, Architecture.arm64, Architecture.universal2},
-            "windows": {Architecture.x86, Architecture.AMD64, Architecture.ARM64},
+            "linux": {Architecture[item] for item in PLATFORM_CATEGORIES["linux"]},
+            "macos": {Architecture[item] for item in PLATFORM_CATEGORIES["macos"]},
+            "windows": {Architecture[item] for item in PLATFORM_CATEGORIES["windows"]},
         }
         return all_archs_map[platform]
 
     @staticmethod
     def bitness_archs(platform: PlatformName, bitness: Literal["64", "32"]) -> set[Architecture]:
-        archs_32 = {Architecture.i686, Architecture.x86}
+        archs_32 = {Architecture[item] for item in ARCH_CATEGORIES["32"]}
         auto_archs = Architecture.auto_archs(platform)
 
         if bitness == "64":

unit_test/architecture_test.py

@@ -0,0 +1,82 @@
+from __future__ import annotations
+
+import platform as platform_module
+import sys
+
+import pytest
+
+from cibuildwheel.architecture import Architecture
+
+
+@pytest.fixture(
+    params=[
+        pytest.param(("linux", "linux", "x86_64", "64"), id="linux-64"),
+        pytest.param(("linux", "linux", "i686", "32"), id="linux-32"),
+        pytest.param(("linux", "linux", "aarch64", "arm"), id="linux-arm"),
+        pytest.param(("macos", "darwin", "x86_64", "64"), id="macos-64"),
+        pytest.param(("macos", "darwin", "arm64", "arm"), id="macos-arm"),
+        pytest.param(("windows", "win32", "x86", "32"), id="windows-32"),
+        pytest.param(("windows", "win32", "AMD64", "64"), id="windows-64"),
+        pytest.param(("windows", "win32", "ARM64", "arm"), id="windows-arm"),
+    ]
+)
+def platform_machine(request, monkeypatch):
+    platform_name, platform_value, machine_value, machine_name = request.param
+    monkeypatch.setattr(sys, "platform", platform_value)
+    monkeypatch.setattr(platform_module, "machine", lambda: machine_value)
+    return platform_name, machine_name
+
+
+def test_arch_auto(platform_machine):
+    platform_name, machine_name = platform_machine
+
+    arch_set = Architecture.auto_archs("linux")
+    expected = {
+        "32": {Architecture.i686},
+        "64": {Architecture.x86_64, Architecture.i686},
+        "arm": {Architecture.aarch64},
+    }
+    assert arch_set == expected[machine_name]
+
+    arch_set = Architecture.auto_archs("macos")
+    expected = {"32": set(), "64": {Architecture.x86_64}, "arm": {Architecture.arm64}}
+    assert arch_set == expected[machine_name]
+
+    arch_set = Architecture.auto_archs("windows")
+    expected = {
+        "32": {Architecture.x86},
+        "64": {Architecture.AMD64, Architecture.x86},
+        "arm": {Architecture.ARM64},
+    }
+    assert arch_set == expected[machine_name]
+
+
+def test_arch_auto64(platform_machine):
+    platform_name, machine_name = platform_machine
+
+    arch_set = Architecture.parse_config("auto64", "linux")
+    expected = {"32": set(), "64": {Architecture.x86_64}, "arm": {Architecture.aarch64}}
+    assert arch_set == expected[machine_name]
+
+    arch_set = Architecture.parse_config("auto64", "macos")
+    expected = {"32": set(), "64": {Architecture.x86_64}, "arm": {Architecture.arm64}}
+    assert arch_set == expected[machine_name]
+
+    arch_set = Architecture.parse_config("auto64", "windows")
+    expected = {"32": set(), "64": {Architecture.AMD64}, "arm": {Architecture.ARM64}}
+    assert arch_set == expected[machine_name]
+
+
+def test_arch_auto32(platform_machine):
+    platform_name, machine_name = platform_machine
+
+    arch_set = Architecture.parse_config("auto32", "linux")
+    expected = {"32": {Architecture.i686}, "64": {Architecture.i686}, "arm": set()}
+    assert arch_set == expected[machine_name]
+
+    arch_set = Architecture.parse_config("auto32", "macos")
+    assert arch_set == set()
+
+    arch_set = Architecture.parse_config("auto32", "windows")
+    expected = {"32": {Architecture.x86}, "64": {Architecture.x86}, "arm": set()}
+    assert arch_set == expected[machine_name]