Add a way to set build configuration values (defines) on swift_library targets.

--
MOS_MIGRATED_REVID=128838998

2 files changed, 45 insertions, 2 deletions

diff --git a/src/test/shell/bazel/bazel_apple_test.sh b/src/test/shell/bazel/bazel_apple_test.sh
index bd78a84e9a..5f56934bfc 100755
--- a/src/test/shell/bazel/bazel_apple_test.sh
+++ b/src/test/shell/bazel/bazel_apple_test.sh
@@ -488,4 +488,33 @@ EOF
     || fail "expected output binary to contain 2 architectures"
 }
 
+function test_swift_defines() {
+  rm -rf ios
+  mkdir -p ios
+
+  cat >ios/main.swift <<EOF
+import Foundation
+
+public class SwiftClass {
+  public func bar() {
+    #if !FLAG
+    let x: String = 1 // Invalid statement, should throw compiler error when FLAG is not set
+    #endif
+  }
+}
+EOF
+
+  cat >ios/BUILD <<EOF
+load("//tools/build_defs/apple:swift.bzl", "swift_library")
+
+swift_library(name = "swift_lib",
+              srcs = ["main.swift"],
+              defines = ["FLAG"])
+EOF
+
+  bazel build --verbose_failures --ios_sdk_version=$IOS_SDK_VERSION \
+      --xcode_version=$XCODE_VERSION \
+      //ios:swift_lib >$TEST_log 2>&1 || fail "should build"
+}
+
 run_suite "apple_tests"
diff --git a/tools/build_defs/apple/swift.bzl b/tools/build_defs/apple/swift.bzl
index 6d4220e311..fe0ca853f1 100644
--- a/tools/build_defs/apple/swift.bzl
+++ b/tools/build_defs/apple/swift.bzl
@@ -136,6 +136,7 @@ def _swift_library_impl(ctx):
 
   include_args = ["-I%s" % d for d in include_dirs + objc_includes]
   framework_args = ["-F%s" % x for x in framework_dirs]
+  define_args = ["-D%s" % x for x in ctx.attr.defines]
 
   clang_args = _intersperse(
       "-Xcc",
@@ -180,6 +181,7 @@ def _swift_library_impl(ctx):
   args.extend(include_args)
   args.extend(framework_args)
   args.extend(clang_args)
+  args.extend(define_args)
 
   xcrun_action(ctx,
                inputs=ctx.files.srcs + dep_modules + list(objc_files) +
@@ -219,6 +221,7 @@ swift_library = rule(
         "srcs": attr.label_list(allow_files = [".swift"]),
         "deps": attr.label_list(providers=[["swift"], ["objc"]]),
         "module_name": attr.string(mandatory=False),
+        "defines": attr.string_list(mandatory=False, allow_empty=True),
         "_xcrunwrapper": attr.label(
             executable=True,
             default=Label(XCRUNWRAPPER_LABEL))},
@@ -235,6 +238,17 @@ Args:
   srcs: Swift sources that comprise this module.
   deps: Other Swift modules.
   module_name: Optional. Sets the Swift module name for this target. By default
-               the module name is the target path with all special symbols
-               replaced by "_", e.g. //foo:bar can be imported as "foo_bar".
+      the module name is the target path with all special symbols replaced
+      by "_", e.g. //foo:bar can be imported as "foo_bar".
+  defines: A list of values for build configuration options (-D). These values
+      can be then used for conditional compilation blocks in code. For example:
+
+      BUILD:
+        swift_library(
+          defines = ["VALUE"]
+        )
+
+      Code:
+        #if VALUE
+        #endif
 """