From 44a86d0b3890848e2df702dc87d625a19216641e Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Wed, 20 Oct 2021 12:05:24 -0400
Subject: cmake_host_system_information: Add undocumented VS_MSBUILD_COMMAND
 key

When using the Visual Studio generator for VS 10 or above,
offer this key to get the location of the MSBuild command
before the first `project()` or `enable_language()` command
has finished running.

This will be needed only by one of our own modules, so leave it
undocumented for now.
---
 Source/cmCMakeHostSystemInformationCommand.cxx                     | 7 +++++++
 Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake    | 6 ++++++
 Tests/RunCMake/cmake_host_system_information/VsMSBuild.cmake       | 4 ++++
 .../cmake_host_system_information/VsMSBuildMissing-result.txt      | 1 +
 .../cmake_host_system_information/VsMSBuildMissing-stderr.txt      | 4 ++++
 .../RunCMake/cmake_host_system_information/VsMSBuildMissing.cmake  | 1 +
 6 files changed, 23 insertions(+)
 create mode 100644 Tests/RunCMake/cmake_host_system_information/VsMSBuild.cmake
 create mode 100644 Tests/RunCMake/cmake_host_system_information/VsMSBuildMissing-result.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/VsMSBuildMissing-stderr.txt
 create mode 100644 Tests/RunCMake/cmake_host_system_information/VsMSBuildMissing.cmake

diff --git a/Source/cmCMakeHostSystemInformationCommand.cxx b/Source/cmCMakeHostSystemInformationCommand.cxx
index 74071ff..3922c56 100644
--- a/Source/cmCMakeHostSystemInformationCommand.cxx
+++ b/Source/cmCMakeHostSystemInformationCommand.cxx
@@ -27,6 +27,7 @@
 #ifdef _WIN32
 #  include "cmAlgorithms.h"
 #  include "cmGlobalGenerator.h"
+#  include "cmGlobalVisualStudio10Generator.h"
 #  include "cmGlobalVisualStudioVersionedGenerator.h"
 #  include "cmVSSetupHelper.h"
 #  define HAVE_VS_SETUP_HELPER
@@ -434,6 +435,12 @@ cm::optional<std::string> GetValue(cmExecutionStatus& status,
     }
   }
 
+  if (key == "VS_MSBUILD_COMMAND"_s && gg->IsVisualStudioAtLeast10()) {
+    cmGlobalVisualStudio10Generator* vs10gen =
+      static_cast<cmGlobalVisualStudio10Generator*>(gg);
+    return vs10gen->FindMSBuildCommandEarly(&status.GetMakefile());
+  }
+
   return {};
 }
 #endif
diff --git a/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake b/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
index 189013f..87b6944 100644
--- a/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
+++ b/Tests/RunCMake/cmake_host_system_information/RunCMakeTest.cmake
@@ -15,3 +15,9 @@ run_cmake(CentOS6)
 run_cmake(Debian6)
 
 run_cmake(UserFallbackScript)
+
+if(RunCMake_GENERATOR MATCHES "^Visual Studio " AND NOT RunCMake_GENERATOR STREQUAL "Visual Studio 9 2008")
+  run_cmake(VsMSBuild)
+else()
+  run_cmake(VsMSBuildMissing)
+endif()
diff --git a/Tests/RunCMake/cmake_host_system_information/VsMSBuild.cmake b/Tests/RunCMake/cmake_host_system_information/VsMSBuild.cmake
new file mode 100644
index 0000000..30e616e
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/VsMSBuild.cmake
@@ -0,0 +1,4 @@
+cmake_host_system_information(RESULT msbuild QUERY VS_MSBUILD_COMMAND)
+if(NOT EXISTS "${msbuild}")
+  message(FATAL_ERROR "VS_MSBUILD_COMMAND returned path that does not exist:\n ${msbuild}")
+endif()
diff --git a/Tests/RunCMake/cmake_host_system_information/VsMSBuildMissing-result.txt b/Tests/RunCMake/cmake_host_system_information/VsMSBuildMissing-result.txt
new file mode 100644
index 0000000..d00491f
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/VsMSBuildMissing-result.txt
@@ -0,0 +1 @@
+1
diff --git a/Tests/RunCMake/cmake_host_system_information/VsMSBuildMissing-stderr.txt b/Tests/RunCMake/cmake_host_system_information/VsMSBuildMissing-stderr.txt
new file mode 100644
index 0000000..3a7dfef
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/VsMSBuildMissing-stderr.txt
@@ -0,0 +1,4 @@
+^CMake Error at VsMSBuildMissing.cmake:[0-9]+ \(cmake_host_system_information\):
+  cmake_host_system_information does not recognize <key> VS_MSBUILD_COMMAND
+Call Stack \(most recent call first\):
+  CMakeLists.txt:[0-9]+ \(include\)$
diff --git a/Tests/RunCMake/cmake_host_system_information/VsMSBuildMissing.cmake b/Tests/RunCMake/cmake_host_system_information/VsMSBuildMissing.cmake
new file mode 100644
index 0000000..23c0364
--- /dev/null
+++ b/Tests/RunCMake/cmake_host_system_information/VsMSBuildMissing.cmake
@@ -0,0 +1 @@
+cmake_host_system_information(RESULT msbuild QUERY VS_MSBUILD_COMMAND)
-- 
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