fix: specify all defines as local using copts (#1094)

In an attempt to localize defines to specific targets, we specify
defines/macros for all target types (e.g., `swift_library`,
`objc_library`, and `cc_library`) targets using `copts`.

Fixes #1093.

Author: cgrindel

swiftpkg/internal/swiftpkg_build_files.bzl

@@ -71,12 +71,13 @@ def _swift_target_build_file(pkg_ctx, target):
             deps_without_plugins = [dep for dep in deps if dep.value[0] not in plugins]
             attrs["deps"] = bzl_selects.to_starlark(deps_without_plugins)
 
-    defines = [
+    # NOTE: We specify defines using copts so that they stay local to the
+    # target. Specifying them using the defines attribute will propagate them.
+    copts = [
         # SPM directive instructing the code to build as if a Swift package.
         # https://github.com/apple/swift-package-manager/blob/main/Documentation/Usage.md#packaging-legacy-code
-        "SWIFT_PACKAGE",
+        "-DSWIFT_PACKAGE",
     ]
-    copts = []
 
     # GH046: Support plugins.
 
@@ -89,8 +90,11 @@ def _swift_target_build_file(pkg_ctx, target):
 
     if target.swift_settings != None:
         if len(target.swift_settings.defines) > 0:
-            defines.extend(lists.flatten([
-                bzl_selects.new_from_build_setting(bs)
+            copts.extend(lists.flatten([
+                bzl_selects.new_from_build_setting(
+                    bs,
+                    values_map_fn = lambda v: "-D" + v,
+                )
                 for bs in target.swift_settings.defines
             ]))
         if len(target.swift_settings.unsafe_flags) > 0:
@@ -103,8 +107,6 @@ def _swift_target_build_file(pkg_ctx, target):
                 copts.append("-enable-experimental-feature")
                 copts.extend(lists.flatten(bzl_selects.new_from_build_setting(bs)))
 
-    if len(defines) > 0:
-        attrs["defines"] = bzl_selects.to_starlark(defines)
     if len(copts) > 0:
         attrs["copts"] = bzl_selects.to_starlark(copts)
 
@@ -233,29 +235,31 @@ def _clang_target_build_file(repository_ctx, pkg_ctx, target):
     if res_build_file:
         all_build_files.append(res_build_file)
 
-    defines = [
-        # The SWIFT_PACKAGE define is a magical value that SPM uses when it
-        # builds clang libraries that will be used as Swift modules.
-        "SWIFT_PACKAGE=1",
-    ]
-
     # The copts may be updated by functions that were executed before this
     # point. Use whatever has been set.
     copts = attrs.get("copts", [])
 
+    # The SWIFT_PACKAGE define is a magical value that SPM uses when it
+    # builds clang libraries that will be used as Swift modules.
+    copts.append("-DSWIFT_PACKAGE=1")
+
     local_includes = [
         bzl_selects.new(value = p, kind = _condition_kinds.private_includes)
         for p in clang_src_info.private_includes
     ]
 
+    def _normalize_and_create_copt_define(value):
+        normalized = scg.normalize_define_value(value)
+        return "-D" + normalized
+
     all_settings = lists.compact([target.clang_settings, target.cxx_settings])
     for settings in all_settings:
-        defines.extend(lists.flatten([
+        copts.extend(lists.flatten([
             bzl_selects.new_from_build_setting(
                 bs,
                 # Define values can contain spaces. Bazel requires that they
                 # are already escaped.
-                values_map_fn = scg.normalize_define_value,
+                values_map_fn = _normalize_and_create_copt_define,
             )
             for bs in settings.defines
         ]))
@@ -336,8 +340,6 @@ def _clang_target_build_file(repository_ctx, pkg_ctx, target):
         },
     )
 
-    attrs["defines"] = bzl_selects.to_starlark(defines)
-
     bzl_target_name = target.label.name
 
     if target.objc_src_info != None:

swiftpkg/tests/swiftpkg_build_files_tests.bzl

@@ -578,7 +578,7 @@ load("@build_bazel_rules_swift//swift:swift.bzl", "swift_library")
 swift_library(
     name = "RegularSwiftTargetAsLibrary.rspm",
     always_include_developer_search_paths = True,
-    defines = ["SWIFT_PACKAGE"],
+    copts = ["-DSWIFT_PACKAGE"],
     deps = [],
     module_name = "RegularSwiftTargetAsLibrary",
     srcs = ["Source/RegularSwiftTargetAsLibrary/RegularSwiftTargetAsLibrary.swift"],
@@ -599,7 +599,7 @@ load("@build_bazel_rules_swift//swift:swift.bzl", "swift_library")
 swift_library(
     name = "RegularTargetForExec.rspm",
     always_include_developer_search_paths = True,
-    defines = ["SWIFT_PACKAGE"],
+    copts = ["-DSWIFT_PACKAGE"],
     deps = ["@swiftpkg_mypackage//:RegularSwiftTargetAsLibrary.rspm"],
     module_name = "RegularTargetForExec",
     srcs = ["Source/RegularTargetForExec/main.swift"],
@@ -616,7 +616,7 @@ load("@build_bazel_rules_swift//swift:swift.bzl", "swift_test")
 
 swift_test(
     name = "RegularSwiftTargetAsLibraryTests.rspm",
-    defines = ["SWIFT_PACKAGE"],
+    copts = ["-DSWIFT_PACKAGE"],
     deps = ["@swiftpkg_mypackage//:RegularSwiftTargetAsLibrary.rspm"],
     module_name = "RegularSwiftTargetAsLibraryTests",
     srcs = ["Tests/RegularSwiftTargetAsLibraryTests/RegularSwiftTargetAsLibraryTests.swift"],
@@ -633,15 +633,15 @@ load("@build_bazel_rules_swift//swift:swift.bzl", "swift_binary")
 swift_binary(
     name = "SwiftExecutableTarget.rspm",
     copts = [
+        "-DSWIFT_PACKAGE",
         "-enable-experimental-feature",
         "BuiltinModule",
     ] + select({
-        "@rules_swift_package_manager//config_settings/spm/configuration:release": ["-cross-module-optimization"],
+        "@rules_swift_package_manager//config_settings/spm/platform:ios": ["-DFOOBAR"],
+        "@rules_swift_package_manager//config_settings/spm/platform:tvos": ["-DFOOBAR"],
         "//conditions:default": [],
-    }),
-    defines = ["SWIFT_PACKAGE"] + select({
-        "@rules_swift_package_manager//config_settings/spm/platform:ios": ["FOOBAR"],
-        "@rules_swift_package_manager//config_settings/spm/platform:tvos": ["FOOBAR"],
+    }) + select({
+        "@rules_swift_package_manager//config_settings/spm/configuration:release": ["-cross-module-optimization"],
         "//conditions:default": [],
     }),
     deps = [],
@@ -663,16 +663,14 @@ cc_library(
         "-fobjc-arc",
         "-fPIC",
         "-fmodule-name=ClangLibrary",
+        "-DSWIFT_PACKAGE=1",
+        "-DPLATFORM_POSIX=1",
         "-Iexternal/bzlmodmangled~swiftpkg_mypackage/src",
         "-Iexternal/bzlmodmangled~swiftpkg_mypackage",
     ] + select({
         "@rules_swift_package_manager//config_settings/spm/configuration:release": ["-danger"],
         "//conditions:default": [],
     }),
-    defines = [
-        "SWIFT_PACKAGE=1",
-        "PLATFORM_POSIX=1",
-    ],
     hdrs = ["include/external.h"],
     includes = ["include"],
     srcs = [
@@ -707,9 +705,9 @@ objc_library(
         "-fobjc-arc",
         "-fPIC",
         "-fmodule-name=ObjcLibrary",
+        "-DSWIFT_PACKAGE=1",
         "-Iexternal/bzlmodmangled~swiftpkg_mypackage/src",
     ],
-    defines = ["SWIFT_PACKAGE=1"],
     deps = [
         "@swiftpkg_mypackage//:ObjcLibraryDep.rspm",
         "@swiftpkg_mypackage//:ObjcLibraryDep.rspm_modulemap",
@@ -766,9 +764,9 @@ objc_library(
         "-fobjc-arc",
         "-fPIC",
         "-fmodule-name=ObjcLibraryWithModulemap",
+        "-DSWIFT_PACKAGE=1",
         "-Iexternal/bzlmodmangled~swiftpkg_mypackage/src",
     ],
-    defines = ["SWIFT_PACKAGE=1"],
     deps = [
         "@swiftpkg_mypackage//:ObjcLibraryDep.rspm",
         "@swiftpkg_mypackage//:ObjcLibraryDep.rspm_modulemap",
@@ -812,7 +810,7 @@ load("@build_bazel_rules_swift//swift:swift.bzl", "swift_library")
 swift_library(
     name = "SwiftLibraryWithConditionalDep.rspm",
     always_include_developer_search_paths = True,
-    defines = ["SWIFT_PACKAGE"],
+    copts = ["-DSWIFT_PACKAGE"],
     deps = ["@swiftpkg_mypackage//:ClangLibrary.rspm"] + select({
         "@rules_swift_package_manager//config_settings/spm/platform:ios": ["@swiftpkg_mypackage//:RegularSwiftTargetAsLibrary.rspm"],
         "@rules_swift_package_manager//config_settings/spm/platform:tvos": ["@swiftpkg_mypackage//:RegularSwiftTargetAsLibrary.rspm"],
@@ -837,9 +835,9 @@ cc_library(
         "-fobjc-arc",
         "-fPIC",
         "-fmodule-name=ClangLibraryWithConditionalDep",
+        "-DSWIFT_PACKAGE=1",
         "-Iexternal/bzlmodmangled~swiftpkg_mypackage/src",
     ],
-    defines = ["SWIFT_PACKAGE=1"],
     deps = select({
         "@rules_swift_package_manager//config_settings/spm/platform:ios": ["@swiftpkg_mypackage//:ClangLibrary.rspm"],
         "@rules_swift_package_manager//config_settings/spm/platform:tvos": ["@swiftpkg_mypackage//:ClangLibrary.rspm"],
@@ -875,7 +873,7 @@ generate_modulemap(
 swift_library(
     name = "SwiftForObjcTarget.rspm",
     always_include_developer_search_paths = True,
-    defines = ["SWIFT_PACKAGE"],
+    copts = ["-DSWIFT_PACKAGE"],
     deps = [
         "@swiftpkg_mypackage//:ObjcLibraryDep.rspm",
         "@swiftpkg_mypackage//:ObjcLibraryDep.rspm_modulemap",
@@ -917,8 +915,8 @@ resource_bundle_infoplist(
 swift_library(
     name = "SwiftLibraryWithFilePathResource.rspm",
     always_include_developer_search_paths = True,
+    copts = ["-DSWIFT_PACKAGE"],
     data = [":SwiftLibraryWithFilePathResource.rspm_resource_bundle"],
-    defines = ["SWIFT_PACKAGE"],
     deps = [],
     module_name = "SwiftLibraryWithFilePathResource",
     srcs = [
@@ -962,10 +960,10 @@ objc_library(
         "-fPIC",
         "-fmodule-name=ObjcLibraryWithResources",
         "-include$(location :ObjcLibraryWithResources.rspm_objc_resource_bundle_accessor_hdr)",
+        "-DSWIFT_PACKAGE=1",
         "-Iexternal/bzlmodmangled~swiftpkg_mypackage/src",
     ],
     data = [":ObjcLibraryWithResources.rspm_resource_bundle"],
-    defines = ["SWIFT_PACKAGE=1"],
     enable_modules = True,
     hdrs = ["include/external.h"],
     includes = ["include"],