From 5cfb8ae79065b900c23c0dafb9b7a90b66bdeca7 Mon Sep 17 00:00:00 2001
From: Ben Boeckel <ben.boeckel@kitware.com>
Date: Thu, 9 Jan 2025 16:23:16 +0100
Subject: Tests/CXXModules: add a test with duplicate sources

See: #26549
---
 Tests/RunCMake/CXXModules/RunCMakeTest.cmake          |  1 +
 .../examples/duplicate-sources/CMakeLists.txt         | 19 +++++++++++++++++++
 .../examples/duplicate-sources/duplicate.cxx          |  8 ++++++++
 .../CXXModules/examples/duplicate-sources/main.cxx    |  6 ++++++
 4 files changed, 34 insertions(+)
 create mode 100644 Tests/RunCMake/CXXModules/examples/duplicate-sources/CMakeLists.txt
 create mode 100644 Tests/RunCMake/CXXModules/examples/duplicate-sources/duplicate.cxx
 create mode 100644 Tests/RunCMake/CXXModules/examples/duplicate-sources/main.cxx

diff --git a/Tests/RunCMake/CXXModules/RunCMakeTest.cmake b/Tests/RunCMake/CXXModules/RunCMakeTest.cmake
index ceb990a..47475d3 100644
--- a/Tests/RunCMake/CXXModules/RunCMakeTest.cmake
+++ b/Tests/RunCMake/CXXModules/RunCMakeTest.cmake
@@ -321,6 +321,7 @@ endif ()
 
 # Tests which require collation work.
 if ("collation" IN_LIST CMake_TEST_MODULE_COMPILATION)
+  run_cxx_module_test(duplicate-sources)
   run_cxx_module_test(public-req-private)
   set(RunCMake_CXXModules_NO_TEST 1)
   run_cxx_module_test(req-private-other-target)
diff --git a/Tests/RunCMake/CXXModules/examples/duplicate-sources/CMakeLists.txt b/Tests/RunCMake/CXXModules/examples/duplicate-sources/CMakeLists.txt
new file mode 100644
index 0000000..b46adaa
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/duplicate-sources/CMakeLists.txt
@@ -0,0 +1,19 @@
+cmake_minimum_required(VERSION 3.31)
+project(cxx_modules_duplicate_sources CXX)
+
+include("${CMAKE_SOURCE_DIR}/../cxx-modules-rules.cmake")
+
+add_executable(duplicate_sources)
+target_sources(duplicate_sources
+  PRIVATE
+    main.cxx
+  PRIVATE
+    FILE_SET CXX_MODULES
+      BASE_DIRS
+        "${CMAKE_CURRENT_SOURCE_DIR}"
+      FILES
+        duplicate.cxx
+        duplicate.cxx)
+target_compile_features(duplicate_sources PRIVATE cxx_std_20)
+
+add_test(NAME duplicate_sources COMMAND duplicate_sources)
diff --git a/Tests/RunCMake/CXXModules/examples/duplicate-sources/duplicate.cxx b/Tests/RunCMake/CXXModules/examples/duplicate-sources/duplicate.cxx
new file mode 100644
index 0000000..39d2178
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/duplicate-sources/duplicate.cxx
@@ -0,0 +1,8 @@
+module;
+
+export module duplicate;
+
+export int from_import()
+{
+  return 0;
+}
diff --git a/Tests/RunCMake/CXXModules/examples/duplicate-sources/main.cxx b/Tests/RunCMake/CXXModules/examples/duplicate-sources/main.cxx
new file mode 100644
index 0000000..bce0322
--- /dev/null
+++ b/Tests/RunCMake/CXXModules/examples/duplicate-sources/main.cxx
@@ -0,0 +1,6 @@
+import duplicate;
+
+int main()
+{
+  return from_import();
+}
-- 
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