fix: filter out maccatalyst SPM platform (#829)

Bazel currently does not support `maccatalyst` as a platform. We were
mapping it to `ios` as they are Mac apps that use iOS frameworks.
However, this can lead to warnings if define values exist with the same
name mapped for `ios` and `maccatalyst` (e.g. Firebase).

This PR filters out `maccatalyst` conditions. 

Closes #801.

config_settings/spm/platform/platforms.bzl

@@ -46,9 +46,6 @@ _PLATFORM_INFOS = [
     _platform_info(spm = p, bzl = None, os = p)
     for p in _NON_APPLE_PLATFORMS
 ] + [
-    # Treat `maccatalyst` as an alias of sorts for macos. This will be handled
-    # in the `platforms.label` function.
-    _platform_info(spm = "maccatalyst", bzl = None, os = None),
     # Map `driverkit` as `macos`. This will be handled in the
     # `platforms.label()` function.
     _platform_info(spm = "driverkit", bzl = None, os = None),
@@ -67,11 +64,17 @@ def _label(name):
     # There is currently no support Mac Catalyst in Bazel. These are Mac apps
     # that use iOS frameworks. Treat it like iOS for now.
     if name == "maccatalyst":
-        name = "ios"
+        fail("Unsupported swift package manager platform: maccatalyst.")
     if name == "driverkit":
         name = "macos"
     return "@rules_swift_package_manager//config_settings/spm/platform:{}".format(name)
 
+def _is_supported(name):
+    return name != "maccatalyst"
+
+def _supported(names):
+    return [n for n in names if _is_supported(n)]
+
 platforms = struct(
     macos = "macos",
     maccatalyst = "maccatalyst",
@@ -86,4 +89,6 @@ platforms = struct(
     all_values = [pi.spm for pi in _PLATFORM_INFOS],
     all_platform_infos = _PLATFORM_INFOS,
     label = _label,
+    is_supported = _is_supported,
+    supported = _supported,
 )

config_settings/spm/tests/platform_tests/BUILD.bazel

@@ -0,0 +1,6 @@
+load("@cgrindel_bazel_starlib//bzlformat:defs.bzl", "bzlformat_pkg")
+load(":platforms_tests.bzl", "platforms_test_suite")
+
+bzlformat_pkg(name = "bzlformat")
+
+platforms_test_suite()

config_settings/spm/tests/platform_tests/platforms_tests.bzl

@@ -0,0 +1,57 @@
+"""Tests for `platforms` module."""
+
+load("@bazel_skylib//lib:unittest.bzl", "asserts", "unittest")
+load("//config_settings/spm/platform:platforms.bzl", "platforms")
+
+def _is_supported_test(ctx):
+    env = unittest.begin(ctx)
+
+    tests = [
+        struct(name = "maccatalyst", exp = False),
+    ] + [
+        struct(name = name, exp = True)
+        for name in platforms.all_values
+    ]
+    for t in tests:
+        actual = platforms.is_supported(t.name)
+        msg = getattr(t, "msg", t.name)
+        asserts.equals(env, t.exp, actual, msg)
+
+    return unittest.end(env)
+
+is_supported_test = unittest.make(_is_supported_test)
+
+def _supported_test(ctx):
+    env = unittest.begin(ctx)
+
+    tests = [
+        struct(
+            msg = "all valid names",
+            names = platforms.all_values,
+            exp = platforms.all_values,
+        ),
+        struct(
+            msg = "some invalid names",
+            names = [platforms.ios, platforms.maccatalyst, platforms.macos],
+            exp = [platforms.ios, platforms.macos],
+        ),
+        struct(
+            msg = "only invalid names",
+            names = [platforms.maccatalyst],
+            exp = [],
+        ),
+    ]
+    for t in tests:
+        actual = platforms.supported(t.names)
+        asserts.equals(env, t.exp, actual, t.msg)
+
+    return unittest.end(env)
+
+supported_test = unittest.make(_supported_test)
+
+def platforms_test_suite(name = "platforms_tests"):
+    return unittest.suite(
+        name,
+        is_supported_test,
+        supported_test,
+    )

swiftpkg/internal/bzl_selects.bzl

@@ -62,20 +62,19 @@ def _new_from_build_setting(build_setting, values_map_fn = None):
             for v in values
         ]
 
-    platforms_len = len(bsc.platforms)
+    supported_platforms = spm_platforms.supported(bsc.platforms)
+    platforms_len = len(supported_platforms)
     if platforms_len > 0 and bsc.configuration != None:
         conditions = [
             spm_platform_configurations.label(p, bsc.configuration)
-            for p in bsc.platforms
+            for p in supported_platforms
         ]
     elif platforms_len > 0:
-        conditions = [spm_platforms.label(p) for p in bsc.platforms]
+        conditions = [spm_platforms.label(p) for p in supported_platforms]
     elif bsc.configuration != None:
         conditions = [spm_configurations.label(bsc.configuration)]
     else:
-        fail("""\
-Found a build setting condition that had no platforms or a configuration. {}\
-""".format(build_setting))
+        return []
 
     return [
         _new(kind = build_setting.kind, value = v, condition = c)
@@ -97,13 +96,12 @@ def _new_from_target_dependency_condition(kind, labels, condition = None):
     """
     if condition == None:
         return [_new(kind = kind, value = labels)]
-    platforms_len = len(condition.platforms)
-    if platforms_len > 0:
-        conditions = [spm_platforms.label(p) for p in condition.platforms]
-    else:
-        fail("""\
-Found a target dependency condition that had no platforms. {}\
-""".format(condition))
+
+    conditions = [
+        spm_platforms.label(p)
+        for p in spm_platforms.supported(condition.platforms)
+    ]
+
     return [
         _new(kind = kind, value = labels, condition = c)
         for c in conditions

swiftpkg/internal/pkginfos.bzl

@@ -1157,13 +1157,7 @@ def _new_build_setting_condition(platforms = [], configuration = None):
     if platforms == [] and configuration == None:
         return None
 
-    for platform in platforms:
-        validations.in_list(
-            spm_platforms.all_values,
-            platform,
-            "Unrecognized platform. platform:",
-        )
-
+    platforms = spm_platforms.supported(platforms)
     if configuration != None:
         validations.in_list(
             spm_configurations.all_values,