From d4aa63212b24e758714916e33417e99baa130453 Mon Sep 17 00:00:00 2001
From: Matt Seaman <mseaman@apple.com>
Date: Thu, 24 Apr 2025 12:52:16 -0700
Subject: [PATCH 1/6] Introduce new defines to enable #bundle in Swift Packages

---
 .../PackagePIFProjectBuilder+Modules.swift           | 12 ++++++++++++
 .../PackagePIFProjectBuilder+Products.swift          |  9 +++++++++
 Sources/XCBuildSupport/PIFBuilder.swift              |  6 ++++++
 3 files changed, 27 insertions(+)

diff --git a/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Modules.swift b/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Modules.swift
index 028c9e537ea..b42e6bc79a9 100644
--- a/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Modules.swift
+++ b/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Modules.swift
@@ -596,6 +596,18 @@ extension PackagePIFProjectBuilder {
             settings[.COREML_COMPILER_CONTAINER] = "swift-package"
         }
 
+        // Leave an explicit indicator regarding whether we are generating a Bundle.module accessor.
+        // This will be read by the #bundle macro defined in Foundation.
+        if !shouldGenerateBundleAccessor {
+            // No resources, so explicitly indicate that.
+            // #bundle will then produce an error about there being no resources.
+            settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS].lazilyInitializeAndMutate(initialValue: ["$(inherited)"]) { $0.append("SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE") }
+        } else if !(resourceBundleName?.isEmpty ?? true) {
+            // We have an explicit resource bundle via Bundle.module.
+            // #bundle should call into that.
+            settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS].lazilyInitializeAndMutate(initialValue: ["$(inherited)"]) { $0.append("SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE") }
+        } // else we won't set either of those and just let #bundle point to the same bundle as the source code.
+
         if desiredModuleType == .macro {
             settings[.SWIFT_IMPLEMENTS_MACROS_FOR_MODULE_NAMES] = [sourceModule.c99name]
         }
diff --git a/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Products.swift b/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Products.swift
index d9cb5d42b7f..6132d2bfb39 100644
--- a/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Products.swift
+++ b/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Products.swift
@@ -245,6 +245,9 @@ extension PackagePIFProjectBuilder {
 
             if result.shouldGenerateBundleAccessor {
                 settings[.GENERATE_RESOURCE_ACCESSORS] = "YES"
+
+                // Do not set `SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE` here since it is just going to point to the same bundle as code.
+                // #bundle can use its default implementation for that.
             }
             if result.shouldGenerateEmbedInCodeAccessor {
                 settings[.GENERATE_EMBED_IN_CODE_ACCESSORS] = "YES"
@@ -264,6 +267,9 @@ extension PackagePIFProjectBuilder {
 
                 if result.shouldGenerateBundleAccessor {
                     settings[.GENERATE_RESOURCE_ACCESSORS] = "YES"
+                    settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS].lazilyInitializeAndMutate(initialValue: ["$(inherited)"]) { $0.append("SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE") }
+                } else {
+                    settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS].lazilyInitializeAndMutate(initialValue: ["$(inherited)"]) { $0.append("SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE") }
                 }
                 if result.shouldGenerateEmbedInCodeAccessor {
                     settings[.GENERATE_EMBED_IN_CODE_ACCESSORS] = "YES"
@@ -305,6 +311,9 @@ extension PackagePIFProjectBuilder {
                 settings[.GENERATE_RESOURCE_ACCESSORS] = "YES"
                 settings[.GENERATE_EMBED_IN_CODE_ACCESSORS] = "NO"
 
+                // Do not set `SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE` here since it is just going to point to the same bundle as code.
+                // #bundle can use its default implementation for that.
+
                 // If we did not create a resource bundle target,
                 // we still need to add build tool commands for any generated files.
                 addBuildToolCommands(
diff --git a/Sources/XCBuildSupport/PIFBuilder.swift b/Sources/XCBuildSupport/PIFBuilder.swift
index 3d020614783..5e8b7ae7b92 100644
--- a/Sources/XCBuildSupport/PIFBuilder.swift
+++ b/Sources/XCBuildSupport/PIFBuilder.swift
@@ -501,6 +501,9 @@ final class PackagePIFProjectBuilder: PIFProjectBuilder {
         if let resourceBundle = addResourceBundle(for: mainTarget, in: pifTarget) {
             settings[.PACKAGE_RESOURCE_BUNDLE_NAME] = resourceBundle
             settings[.GENERATE_RESOURCE_ACCESSORS] = "YES"
+            settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS, default: ["$(inherited)"]].append("SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE")
+        } else {
+            settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS, default: ["$(inherited)"]].append("SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE")
         }
 
         // For targets, we use the common build settings for both the "Debug" and the "Release" configurations (all
@@ -729,7 +732,10 @@ final class PackagePIFProjectBuilder: PIFProjectBuilder {
         if let resourceBundle = addResourceBundle(for: target, in: pifTarget) {
             settings[.PACKAGE_RESOURCE_BUNDLE_NAME] = resourceBundle
             settings[.GENERATE_RESOURCE_ACCESSORS] = "YES"
+            settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS, default: ["$(inherited)"]].append("SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE")
             impartedSettings[.EMBED_PACKAGE_RESOURCE_BUNDLE_NAMES, default: ["$(inherited)"]].append(resourceBundle)
+        } else {
+            settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS, default: ["$(inherited)"]].append("SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE")
         }
 
         // For targets, we use the common build settings for both the "Debug" and the "Release" configurations (all

From 68b530ad963a4122614026ab7f4253a0d9e3f56a Mon Sep 17 00:00:00 2001
From: Matt Seaman <mseaman@apple.com>
Date: Thu, 24 Apr 2025 13:18:57 -0700
Subject: [PATCH 2/6] Implement for vanilla SwiftPM builds

---
 .../BuildDescription/ClangModuleBuildDescription.swift      | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Sources/Build/BuildDescription/ClangModuleBuildDescription.swift b/Sources/Build/BuildDescription/ClangModuleBuildDescription.swift
index 3aadda6b52b..75d06aa08a9 100644
--- a/Sources/Build/BuildDescription/ClangModuleBuildDescription.swift
+++ b/Sources/Build/BuildDescription/ClangModuleBuildDescription.swift
@@ -455,6 +455,12 @@ public final class ClangModuleBuildDescription {
             break
         }
 
+        if bundlePath != nil {
+            compilationConditions += ["-DSWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE=1"]
+        } else {
+            compilationConditions += ["-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE=1"]
+        }
+
         return compilationConditions
     }
 

From 1d8be60c78449c7f711f72a40cf555f144f43a41 Mon Sep 17 00:00:00 2001
From: Matt Seaman <mseaman@apple.com>
Date: Thu, 24 Apr 2025 13:24:23 -0700
Subject: [PATCH 3/6] Move from ClangModule to SwiftModule

---
 .../BuildDescription/ClangModuleBuildDescription.swift      | 6 ------
 .../BuildDescription/SwiftModuleBuildDescription.swift      | 6 ++++++
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Sources/Build/BuildDescription/ClangModuleBuildDescription.swift b/Sources/Build/BuildDescription/ClangModuleBuildDescription.swift
index 75d06aa08a9..3aadda6b52b 100644
--- a/Sources/Build/BuildDescription/ClangModuleBuildDescription.swift
+++ b/Sources/Build/BuildDescription/ClangModuleBuildDescription.swift
@@ -455,12 +455,6 @@ public final class ClangModuleBuildDescription {
             break
         }
 
-        if bundlePath != nil {
-            compilationConditions += ["-DSWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE=1"]
-        } else {
-            compilationConditions += ["-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE=1"]
-        }
-
         return compilationConditions
     }
 
diff --git a/Sources/Build/BuildDescription/SwiftModuleBuildDescription.swift b/Sources/Build/BuildDescription/SwiftModuleBuildDescription.swift
index 89f2637ff0b..b8b4fc0f00f 100644
--- a/Sources/Build/BuildDescription/SwiftModuleBuildDescription.swift
+++ b/Sources/Build/BuildDescription/SwiftModuleBuildDescription.swift
@@ -969,6 +969,12 @@ public final class SwiftModuleBuildDescription {
             break
         }
 
+        if bundlePath != nil {
+            compilationConditions += ["-DSWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE=1"]
+        } else {
+            compilationConditions += ["-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE=1"]
+        }
+
         return compilationConditions
     }
 

From 617eec68e2c4f5b14633d342af454d4011480ae6 Mon Sep 17 00:00:00 2001
From: Matt Seaman <mseaman@apple.com>
Date: Thu, 24 Apr 2025 13:46:51 -0700
Subject: [PATCH 4/6] Use non-value form of defines for Swift

---
 .../Build/BuildDescription/SwiftModuleBuildDescription.swift  | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Sources/Build/BuildDescription/SwiftModuleBuildDescription.swift b/Sources/Build/BuildDescription/SwiftModuleBuildDescription.swift
index b8b4fc0f00f..721153fb251 100644
--- a/Sources/Build/BuildDescription/SwiftModuleBuildDescription.swift
+++ b/Sources/Build/BuildDescription/SwiftModuleBuildDescription.swift
@@ -970,9 +970,9 @@ public final class SwiftModuleBuildDescription {
         }
 
         if bundlePath != nil {
-            compilationConditions += ["-DSWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE=1"]
+            compilationConditions += ["-DSWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE"]
         } else {
-            compilationConditions += ["-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE=1"]
+            compilationConditions += ["-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE"]
         }
 
         return compilationConditions

From 5b8637d7aeb176c0e1609fc4c4919e538bc23df5 Mon Sep 17 00:00:00 2001
From: Matt Seaman <mseaman@apple.com>
Date: Thu, 24 Apr 2025 18:28:12 -0700
Subject: [PATCH 5/6] Only define these for Swift modules

---
 .../PackagePIFProjectBuilder+Modules.swift    | 24 ++++++++++---------
 .../PackagePIFProjectBuilder+Products.swift   |  7 ++++--
 Sources/XCBuildSupport/PIFBuilder.swift       | 17 +++++++++----
 3 files changed, 31 insertions(+), 17 deletions(-)

diff --git a/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Modules.swift b/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Modules.swift
index b42e6bc79a9..c7204032eb2 100644
--- a/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Modules.swift
+++ b/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Modules.swift
@@ -596,17 +596,19 @@ extension PackagePIFProjectBuilder {
             settings[.COREML_COMPILER_CONTAINER] = "swift-package"
         }
 
-        // Leave an explicit indicator regarding whether we are generating a Bundle.module accessor.
-        // This will be read by the #bundle macro defined in Foundation.
-        if !shouldGenerateBundleAccessor {
-            // No resources, so explicitly indicate that.
-            // #bundle will then produce an error about there being no resources.
-            settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS].lazilyInitializeAndMutate(initialValue: ["$(inherited)"]) { $0.append("SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE") }
-        } else if !(resourceBundleName?.isEmpty ?? true) {
-            // We have an explicit resource bundle via Bundle.module.
-            // #bundle should call into that.
-            settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS].lazilyInitializeAndMutate(initialValue: ["$(inherited)"]) { $0.append("SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE") }
-        } // else we won't set either of those and just let #bundle point to the same bundle as the source code.
+        if sourceModule.usesSwift {
+            // Leave an explicit indicator regarding whether we are generating a Bundle.module accessor.
+            // This will be read by the #bundle macro defined in Foundation.
+            if !shouldGenerateBundleAccessor {
+                // No resources, so explicitly indicate that.
+                // #bundle will then produce an error about there being no resources.
+                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS].lazilyInitializeAndMutate(initialValue: ["$(inherited)"]) { $0.append("SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE") }
+            } else if !(resourceBundleName?.isEmpty ?? true) {
+                // We have an explicit resource bundle via Bundle.module.
+                // #bundle should call into that.
+                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS].lazilyInitializeAndMutate(initialValue: ["$(inherited)"]) { $0.append("SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE") }
+            } // else we won't set either of those and just let #bundle point to the same bundle as the source code.
+        }
 
         if desiredModuleType == .macro {
             settings[.SWIFT_IMPLEMENTS_MACROS_FOR_MODULE_NAMES] = [sourceModule.c99name]
diff --git a/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Products.swift b/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Products.swift
index 6132d2bfb39..32abc8fd371 100644
--- a/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Products.swift
+++ b/Sources/SwiftBuildSupport/PackagePIFProjectBuilder+Products.swift
@@ -267,8 +267,11 @@ extension PackagePIFProjectBuilder {
 
                 if result.shouldGenerateBundleAccessor {
                     settings[.GENERATE_RESOURCE_ACCESSORS] = "YES"
-                    settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS].lazilyInitializeAndMutate(initialValue: ["$(inherited)"]) { $0.append("SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE") }
-                } else {
+
+                    if mainModule.usesSwift {
+                        settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS].lazilyInitializeAndMutate(initialValue: ["$(inherited)"]) { $0.append("SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE") }
+                    }
+                } else if mainModule.usesSwift {
                     settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS].lazilyInitializeAndMutate(initialValue: ["$(inherited)"]) { $0.append("SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE") }
                 }
                 if result.shouldGenerateEmbedInCodeAccessor {
diff --git a/Sources/XCBuildSupport/PIFBuilder.swift b/Sources/XCBuildSupport/PIFBuilder.swift
index 5e8b7ae7b92..283379fedd1 100644
--- a/Sources/XCBuildSupport/PIFBuilder.swift
+++ b/Sources/XCBuildSupport/PIFBuilder.swift
@@ -488,12 +488,14 @@ final class PackagePIFProjectBuilder: PIFProjectBuilder {
             settings[.GENERATE_INFOPLIST_FILE] = "YES"
         }
 
+        var isSwiftModule = false
         if let clangTarget = mainTarget.underlying as? ClangModule {
             // Let the target itself find its own headers.
             settings[.HEADER_SEARCH_PATHS, default: ["$(inherited)"]].append(clangTarget.includeDir.pathString)
             settings[.GCC_C_LANGUAGE_STANDARD] = clangTarget.cLanguageStandard
             settings[.CLANG_CXX_LANGUAGE_STANDARD] = clangTarget.cxxLanguageStandard
         } else if let swiftTarget = mainTarget.underlying as? SwiftModule {
+            isSwiftModule = true
             try settings.addSwiftVersionSettings(target: swiftTarget, parameters: self.parameters)
             settings.addCommonSwiftSettings(package: self.package, target: mainTarget, parameters: self.parameters)
         }
@@ -501,8 +503,11 @@ final class PackagePIFProjectBuilder: PIFProjectBuilder {
         if let resourceBundle = addResourceBundle(for: mainTarget, in: pifTarget) {
             settings[.PACKAGE_RESOURCE_BUNDLE_NAME] = resourceBundle
             settings[.GENERATE_RESOURCE_ACCESSORS] = "YES"
-            settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS, default: ["$(inherited)"]].append("SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE")
-        } else {
+
+            if isSwiftModule {
+                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS, default: ["$(inherited)"]].append("SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE")
+            }
+        } else if isSwiftModule {
             settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS, default: ["$(inherited)"]].append("SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE")
         }
 
@@ -657,6 +662,7 @@ final class PackagePIFProjectBuilder: PIFProjectBuilder {
         let moduleMapFileContents: String?
         let shouldImpartModuleMap: Bool
 
+        var isSwiftModule = false
         if let clangTarget = target.underlying as? ClangModule {
             // Let the target itself find its own headers.
             settings[.HEADER_SEARCH_PATHS, default: ["$(inherited)"]].append(clangTarget.includeDir.pathString)
@@ -683,6 +689,7 @@ final class PackagePIFProjectBuilder: PIFProjectBuilder {
                 shouldImpartModuleMap = false
             }
         } else if let swiftTarget = target.underlying as? SwiftModule {
+            isSwiftModule = true
             try settings.addSwiftVersionSettings(target: swiftTarget, parameters: self.parameters)
 
             // Generate ObjC compatibility header for Swift library targets.
@@ -732,9 +739,11 @@ final class PackagePIFProjectBuilder: PIFProjectBuilder {
         if let resourceBundle = addResourceBundle(for: target, in: pifTarget) {
             settings[.PACKAGE_RESOURCE_BUNDLE_NAME] = resourceBundle
             settings[.GENERATE_RESOURCE_ACCESSORS] = "YES"
-            settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS, default: ["$(inherited)"]].append("SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE")
+            if isSwiftModule {
+                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS, default: ["$(inherited)"]].append("SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE")
+            }
             impartedSettings[.EMBED_PACKAGE_RESOURCE_BUNDLE_NAMES, default: ["$(inherited)"]].append(resourceBundle)
-        } else {
+        } else if isSwiftModule {
             settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS, default: ["$(inherited)"]].append("SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE")
         }
 

From c052c5476765e6bd23a110e95090c359071920be Mon Sep 17 00:00:00 2001
From: Matt Seaman <mseaman@apple.com>
Date: Thu, 24 Apr 2025 18:28:29 -0700
Subject: [PATCH 6/6] Update unit tests

---
 Tests/BuildTests/BuildPlanTests.swift         | 16 ++++-
 .../CrossCompilationBuildPlanTests.swift      |  2 +-
 .../XCBuildSupportTests/PIFBuilderTests.swift | 64 +++++++++++++++++--
 3 files changed, 76 insertions(+), 6 deletions(-)

diff --git a/Tests/BuildTests/BuildPlanTests.swift b/Tests/BuildTests/BuildPlanTests.swift
index 914b46130a4..a526f38f4d9 100644
--- a/Tests/BuildTests/BuildPlanTests.swift
+++ b/Tests/BuildTests/BuildPlanTests.swift
@@ -792,6 +792,7 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
                 .equal(self.j),
                 "-DSWIFT_PACKAGE",
                 "-DDEBUG",
+                "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE",
                 "-module-cache-path", "\(buildPath.appending(components: "ModuleCache"))",
                 .anySequence,
                 "-swift-version", "4",
@@ -811,6 +812,7 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
                 .equal(self.j),
                 "-DSWIFT_PACKAGE",
                 "-DDEBUG",
+                "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE",
                 "-module-cache-path", "\(buildPath.appending(components: "ModuleCache"))",
                 .anySequence,
                 "-swift-version", "4",
@@ -1224,6 +1226,7 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
                 "-O",
                 .equal(self.j),
                 "-DSWIFT_PACKAGE",
+                "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE",
                 "-module-cache-path", "\(buildPath.appending(components: "ModuleCache"))",
                 .anySequence,
                 "-swift-version", "4",
@@ -1318,6 +1321,7 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
                 "-O",
                 .equal(self.j),
                 "-DSWIFT_PACKAGE",
+                "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE",
                 "-module-cache-path", "\(buildPath.appending(components: "ModuleCache"))",
                 .anySequence,
                 "-swift-version", "4",
@@ -1863,6 +1867,7 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
                 .equal(self.j),
                 "-DSWIFT_PACKAGE",
                 "-DDEBUG",
+                "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE",
                 "-Xcc",
                 "-fmodule-map-file=\(buildPath.appending(components: "lib.build", "module.modulemap"))",
                 "-Xcc", "-I", "-Xcc", "\(Pkg.appending(components: "Sources", "lib", "include"))",
@@ -2365,6 +2370,7 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
                 .equal(self.j),
                 "-DSWIFT_PACKAGE",
                 "-DDEBUG",
+                "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE",
                 "-module-cache-path", "\(buildPath.appending(components: "ModuleCache"))",
                 .anySequence,
                 "-swift-version", "4",
@@ -2387,6 +2393,7 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
                 .equal(self.j),
                 "-DSWIFT_PACKAGE",
                 "-DDEBUG",
+                "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE",
                 "-module-cache-path", "\(buildPath.appending(components: "ModuleCache"))",
                 .anySequence,
                 "-swift-version", "4",
@@ -2499,6 +2506,7 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
                 "-O",
                 .equal(self.j),
                 "-DSWIFT_PACKAGE",
+                "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE",
                 "-module-cache-path", "\(buildPath.appending(components: "ModuleCache"))",
                 .anySequence,
                 "-swift-version", "4",
@@ -2864,6 +2872,7 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
             .equal(self.j),
             "-DSWIFT_PACKAGE",
             "-DDEBUG",
+            "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE",
             "-Xcc", "-fmodule-map-file=\(Clibgit.appending(components: "module.modulemap"))",
             "-module-cache-path", "\(buildPath.appending(components: "ModuleCache"))",
             .anySequence,
@@ -3166,6 +3175,7 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
                 .equal(self.j),
                 "-DSWIFT_PACKAGE",
                 "-DDEBUG",
+                "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE",
                 "-module-cache-path", "\(buildPath.appending(components: "ModuleCache"))",
                 .anySequence,
                 "-swift-version", "4",
@@ -3185,6 +3195,7 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
                 .equal(self.j),
                 "-DSWIFT_PACKAGE",
                 "-DDEBUG",
+                "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE",
                 "-module-cache-path", "\(buildPath.appending(components: "ModuleCache"))",
                 .anySequence,
                 "-swift-version", "4",
@@ -3824,7 +3835,7 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
             "-Onone",
             "-enable-testing",
             .equal(self.j),
-            "-DSWIFT_PACKAGE", "-DDEBUG",
+            "-DSWIFT_PACKAGE", "-DDEBUG", "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE",
             "-Xcc", "-fmodule-map-file=\(buildPath.appending(components: "lib.build", "module.modulemap"))",
             "-Xcc", "-I", "-Xcc", "\(Pkg.appending(components: "Sources", "lib", "include"))",
             "-module-cache-path", "\(buildPath.appending(components: "ModuleCache"))",
@@ -5888,6 +5899,9 @@ class BuildPlanTestCase: BuildSystemProviderTestCase {
         XCTAssertEqual(try barTarget.objects.map(\.pathString), [
             buildPath.appending(components: "Bar.build", "Bar.swift.o").pathString,
         ])
+
+        XCTAssertTrue(try fooTarget.compileArguments().contains(["-DSWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE"]))
+        XCTAssertTrue(try barTarget.compileArguments().contains(["-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE"]))
     }
 
     func testSwiftWASIBundleAccessor() async throws {
diff --git a/Tests/BuildTests/CrossCompilationBuildPlanTests.swift b/Tests/BuildTests/CrossCompilationBuildPlanTests.swift
index 698ad2c8183..27a5412487b 100644
--- a/Tests/BuildTests/CrossCompilationBuildPlanTests.swift
+++ b/Tests/BuildTests/CrossCompilationBuildPlanTests.swift
@@ -179,7 +179,7 @@ final class CrossCompilationBuildPlanTests: XCTestCase {
             exe,
             [
                 "-enable-batch-mode", "-serialize-diagnostics", "-Onone", "-enable-testing",
-                "-j3", "-DSWIFT_PACKAGE", "-DDEBUG", "-Xcc",
+                "-j3", "-DSWIFT_PACKAGE", "-DDEBUG", "-DSWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE", "-Xcc",
                 "-fmodule-map-file=\(buildPath.appending(components: "lib.build", "module.modulemap"))",
                 "-Xcc", "-I", "-Xcc", "\(pkgPath.appending(components: "Sources", "lib", "include"))",
                 "-module-cache-path", "\(buildPath.appending(components: "ModuleCache"))", .anySequence,
diff --git a/Tests/XCBuildSupportTests/PIFBuilderTests.swift b/Tests/XCBuildSupportTests/PIFBuilderTests.swift
index 172d59f255b..3d380a77dcf 100644
--- a/Tests/XCBuildSupportTests/PIFBuilderTests.swift
+++ b/Tests/XCBuildSupportTests/PIFBuilderTests.swift
@@ -542,6 +542,10 @@ final class PIFBuilderTests: XCTestCase {
                                 settings[.LIBRARY_SEARCH_PATHS],
                                 ["$(inherited)", "/toolchain/lib/swift/macosx"]
                             )
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE"]
+                            )
                         }
                     }
 
@@ -567,6 +571,10 @@ final class PIFBuilderTests: XCTestCase {
                                 settings[.LIBRARY_SEARCH_PATHS],
                                 ["$(inherited)", "/toolchain/lib/swift/macosx"]
                             )
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE"]
+                            )
                         }
                     }
 
@@ -671,6 +679,10 @@ final class PIFBuilderTests: XCTestCase {
                                 settings[.LIBRARY_SEARCH_PATHS],
                                 ["$(inherited)", "/toolchain/lib/swift/macosx"]
                             )
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE"]
+                            )
                         }
                     }
 
@@ -690,6 +702,10 @@ final class PIFBuilderTests: XCTestCase {
                                 settings[.LIBRARY_SEARCH_PATHS],
                                 ["$(inherited)", "/toolchain/lib/swift/macosx"]
                             )
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE"]
+                            )
                         }
                     }
 
@@ -877,6 +893,10 @@ final class PIFBuilderTests: XCTestCase {
                                 "$(inherited)",
                                 "/toolchain/lib/swift/macosx",
                             ])
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE"]
+                            )
                             XCTAssertEqual(settings[.PACKAGE_RESOURCE_TARGET_KIND], "regular")
                             XCTAssertEqual(settings[.PRODUCT_BUNDLE_IDENTIFIER], "FooTests")
                             XCTAssertEqual(settings[.PRODUCT_MODULE_NAME], "FooTests")
@@ -924,6 +944,10 @@ final class PIFBuilderTests: XCTestCase {
                                 "$(inherited)",
                                 "/toolchain/lib/swift/macosx",
                             ])
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE"]
+                            )
                             XCTAssertEqual(settings[.PACKAGE_RESOURCE_TARGET_KIND], "regular")
                             XCTAssertEqual(settings[.PRODUCT_BUNDLE_IDENTIFIER], "FooTests")
                             XCTAssertEqual(settings[.PRODUCT_MODULE_NAME], "FooTests")
@@ -1395,6 +1419,10 @@ final class PIFBuilderTests: XCTestCase {
                             XCTAssertEqual(settings[.SWIFT_OBJC_INTERFACE_HEADER_NAME], "FooLib1-Swift.h")
                             XCTAssertEqual(settings[.SWIFT_VERSION], "5")
                             XCTAssertEqual(settings[.TARGET_NAME], "FooLib1_Module")
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE"]
+                            )
                         }
                     }
 
@@ -1428,6 +1456,10 @@ final class PIFBuilderTests: XCTestCase {
                             XCTAssertEqual(settings[.SWIFT_OBJC_INTERFACE_HEADER_NAME], "FooLib1-Swift.h")
                             XCTAssertEqual(settings[.SWIFT_VERSION], "5")
                             XCTAssertEqual(settings[.TARGET_NAME], "FooLib1_Module")
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_UNAVAILABLE"]
+                            )
                         }
                     }
 
@@ -2224,12 +2256,20 @@ final class PIFBuilderTests: XCTestCase {
                     target.checkBuildConfiguration("Debug") { configuration in
                         configuration.checkBuildSettings { settings in
                             XCTAssertEqual(settings[.PACKAGE_RESOURCE_BUNDLE_NAME], "Foo_foo")
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE"]
+                            )
                         }
                     }
 
-                    target.checkBuildConfiguration("Debug") { configuration in
+                    target.checkBuildConfiguration("Release") { configuration in
                         configuration.checkBuildSettings { settings in
                             XCTAssertEqual(settings[.PACKAGE_RESOURCE_BUNDLE_NAME], "Foo_foo")
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE"]
+                            )
                         }
                     }
 
@@ -2287,7 +2327,7 @@ final class PIFBuilderTests: XCTestCase {
                         }
                     }
 
-                    target.checkBuildConfiguration("Debug") { configuration in
+                    target.checkBuildConfiguration("Release") { configuration in
                         configuration.checkBuildSettings { settings in
                             XCTAssertEqual(settings[.PACKAGE_RESOURCE_BUNDLE_NAME], nil)
                         }
@@ -2305,12 +2345,20 @@ final class PIFBuilderTests: XCTestCase {
                     target.checkBuildConfiguration("Debug") { configuration in
                         configuration.checkBuildSettings { settings in
                             XCTAssertEqual(settings[.PACKAGE_RESOURCE_BUNDLE_NAME], "Foo_FooLib")
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE"]
+                            )
                         }
                     }
 
-                    target.checkBuildConfiguration("Debug") { configuration in
+                    target.checkBuildConfiguration("Release") { configuration in
                         configuration.checkBuildSettings { settings in
                             XCTAssertEqual(settings[.PACKAGE_RESOURCE_BUNDLE_NAME], "Foo_FooLib")
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE"]
+                            )
                         }
                     }
 
@@ -2326,12 +2374,20 @@ final class PIFBuilderTests: XCTestCase {
                     target.checkBuildConfiguration("Debug") { configuration in
                         configuration.checkBuildSettings { settings in
                             XCTAssertEqual(settings[.PACKAGE_RESOURCE_BUNDLE_NAME], "Foo_FooTests")
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE"]
+                            )
                         }
                     }
 
-                    target.checkBuildConfiguration("Debug") { configuration in
+                    target.checkBuildConfiguration("Release") { configuration in
                         configuration.checkBuildSettings { settings in
                             XCTAssertEqual(settings[.PACKAGE_RESOURCE_BUNDLE_NAME], "Foo_FooTests")
+                            XCTAssertEqual(
+                                settings[.SWIFT_ACTIVE_COMPILATION_CONDITIONS],
+                                ["$(inherited)", "SWIFT_MODULE_RESOURCE_BUNDLE_AVAILABLE"]
+                            )
                         }
                     }