From 7239481fef6bf807056043bb1970c0b47514b676 Mon Sep 17 00:00:00 2001
From: Eric Miotto <emiotto@apple.com>
Date: Thu, 16 Oct 2025 10:27:35 -0700
Subject: [PATCH] CMake: add Observation dependency to libraries that import
 Foundation...

when building for Apple platforms.

In this scenario we are not building our own Foundation,
but we are importing the one from the underlying SDK -- this in turns
requires Observation, which is something we typically build.

Addresses rdar://162286123
---
 stdlib/private/StdlibUnicodeUnittest/CMakeLists.txt  | 12 ++++++++++++
 stdlib/private/StdlibUnittest/CMakeLists.txt         |  6 ++++++
 .../StdlibUnittestFoundationExtras/CMakeLists.txt    | 12 ++++++++++++
 3 files changed, 30 insertions(+)

diff --git a/stdlib/private/StdlibUnicodeUnittest/CMakeLists.txt b/stdlib/private/StdlibUnicodeUnittest/CMakeLists.txt
index e1a1eec87b67d..f769659817e29 100644
--- a/stdlib/private/StdlibUnicodeUnittest/CMakeLists.txt
+++ b/stdlib/private/StdlibUnicodeUnittest/CMakeLists.txt
@@ -1,5 +1,11 @@
 set(swift_stdlib_unittest_compile_flags)
 
+if(SWIFT_ENABLE_EXPERIMENTAL_OBSERVATION)
+  # This library imports Foundation from the SDK, which re-exports
+  # Observation which is part of this build.
+  list(APPEND swift_stdlib_unicode_unittest_darwin_dependencies Observation)
+endif()
+
 add_swift_target_library(swiftStdlibUnicodeUnittest ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_STDLIB
   # This file should be listed the first.  Module name is inferred from the
   # filename.
@@ -10,6 +16,12 @@ add_swift_target_library(swiftStdlibUnicodeUnittest ${SWIFT_STDLIB_LIBRARY_BUILD
   WordBreaking.swift
 
   SWIFT_MODULE_DEPENDS StdlibUnittest
+  SWIFT_MODULE_DEPENDS_IOS ${swift_stdlib_unicode_unittest_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_OSX ${swift_stdlib_unicode_unittest_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_TVOS ${swift_stdlib_unicode_unittest_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_WATCHOS ${swift_stdlib_unicode_unittest_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_XROS ${swift_stdlib_unicode_unittest_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_MACCATALYST ${swift_stdlib_unicode_unittest_darwin_dependencies}
   SWIFT_MODULE_DEPENDS_ANDROID Android
   SWIFT_MODULE_DEPENDS_LINUX Glibc
   SWIFT_MODULE_DEPENDS_LINUX_STATIC Musl
diff --git a/stdlib/private/StdlibUnittest/CMakeLists.txt b/stdlib/private/StdlibUnittest/CMakeLists.txt
index 6fee7d239c8bf..7a0c7405cc2ee 100644
--- a/stdlib/private/StdlibUnittest/CMakeLists.txt
+++ b/stdlib/private/StdlibUnittest/CMakeLists.txt
@@ -9,6 +9,12 @@ if((SWIFT_BUILD_CLANG_OVERLAYS
   list(APPEND swift_stdlib_unittest_darwin_dependencies _Builtin_float)
 endif()
 
+if(SWIFT_ENABLE_EXPERIMENTAL_OBSERVATION)
+  # This library imports Foundation from the SDK, which re-exports
+  # Observation which is part of this build.
+  list(APPEND swift_stdlib_unittest_darwin_dependencies Observation)
+endif()
+
 set(swift_stdlib_unittest_compile_flags
   "-Xfrontend" "-disable-objc-attr-requires-foundation-module")
 
diff --git a/stdlib/private/StdlibUnittestFoundationExtras/CMakeLists.txt b/stdlib/private/StdlibUnittestFoundationExtras/CMakeLists.txt
index 2a9374a0b2160..ffcb3259043e8 100644
--- a/stdlib/private/StdlibUnittestFoundationExtras/CMakeLists.txt
+++ b/stdlib/private/StdlibUnittestFoundationExtras/CMakeLists.txt
@@ -1,9 +1,21 @@
+if(SWIFT_ENABLE_EXPERIMENTAL_OBSERVATION)
+  # This library imports Foundation from the SDK, which re-exports
+  # Observation which is part of this build.
+  list(APPEND swift_stdlib_unittest_foundationextras_darwin_dependencies Observation)
+endif()
+
 add_swift_target_library(swiftStdlibUnittestFoundationExtras ${SWIFT_STDLIB_LIBRARY_BUILD_TYPES} IS_STDLIB
   # This file should be listed the first.  Module name is inferred from the
   # filename.
   StdlibUnittestFoundationExtras.swift
   UnavailableFoundationMethodThunks.mm
 
+  SWIFT_MODULE_DEPENDS_IOS ${swift_stdlib_unittest_foundationextras_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_OSX ${swift_stdlib_unittest_foundationextras_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_TVOS ${swift_stdlib_unittest_foundationextras_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_WATCHOS ${swift_stdlib_unittest_foundationextras_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_XROS ${swift_stdlib_unittest_foundationextras_darwin_dependencies}
+  SWIFT_MODULE_DEPENDS_MACCATALYST ${swift_stdlib_unittest_foundationextras_darwin_dependencies}
   SWIFT_MODULE_DEPENDS StdlibUnittest
   SWIFT_COMPILE_FLAGS ${SWIFT_STANDARD_LIBRARY_SWIFT_FLAGS}
   INSTALL_IN_COMPONENT stdlib-experimental