Experimental: provide useful warning for invalid experimental variable values

Provide a useful warning if an invalid UUID is given in a
`CMAKE_EXPERIMENTAL_` variable.  This can occur if a different CMake
version is used than the one that the feature was implemented with, or
if there is a simple typo in the value.  It should reduce confusion with
the use of experimental features.

Co-authored-by: Brad King <[email protected]>

Source/cmExperimental.cxx

@@ -10,6 +10,7 @@
 #include "cmGlobalGenerator.h"
 #include "cmMakefile.h"
 #include "cmMessageType.h"
+#include "cmStringAlgorithms.h"
 #include "cmValue.h"
 
 namespace {
@@ -120,6 +121,16 @@ bool cmExperimental::HasSupportEnabled(cmMakefile const& mf, Feature f)
     if (mf.GetGlobalGenerator()->ShouldWarnExperimental(data.Name, *value)) {
       if (enabled) {
         mf.IssueMessage(MessageType::AUTHOR_WARNING, data.Description);
+      } else {
+        mf.IssueMessage(
+          MessageType::AUTHOR_WARNING,
+          cmStrCat(
+            data.Variable, " is set to incorrect value\n  ", value, '\n',
+            "See 'Help/dev/experimental.rst' in the source tree of this "
+            "version of CMake for documentation of the experimental feature "
+            "and the corresponding activation value.  This project's code "
+            "may require changes to work with this CMake's version of the "
+            "feature."));
       }
     }
   }

Tests/RunCMake/cmake_language/Experimental/CxxImportStd-wrong-stderr.txt

@@ -0,0 +1,25 @@
+^CMake Warning \(dev\) at Experimental/CxxImportStd-wrong\.cmake:4 \(cmake_language\):
+  CMAKE_EXPERIMENTAL_CXX_IMPORT_STD is set to incorrect value
+
+    01234567-0123-0123-0123-0123456789ab
+
+  See 'Help/dev/experimental\.rst' in the source tree of this version of CMake
+  for documentation of the experimental feature and the corresponding
+  activation value\.  This project's code may require changes to work with
+  this CMake's version of the feature\.
+Call Stack \(most recent call first\):
+  CMakeLists\.txt:[0-9]+ \(include\)
+This warning is for project developers\.  Use -Wno-dev to suppress it\.
++
+CMake Warning \(dev\) at Experimental/CxxImportStd-wrong\.cmake:19 \(cmake_language\):
+  CMAKE_EXPERIMENTAL_CXX_IMPORT_STD is set to incorrect value
+
+    76543210-3210-3210-3210-ba9876543210
+
+  See 'Help/dev/experimental\.rst' in the source tree of this version of CMake
+  for documentation of the experimental feature and the corresponding
+  activation value\.  This project's code may require changes to work with
+  this CMake's version of the feature\.
+Call Stack \(most recent call first\):
+  CMakeLists\.txt:[0-9]+ \(include\)
+This warning is for project developers\.  Use -Wno-dev to suppress it\.$

Tests/RunCMake/cmake_language/Experimental/CxxImportStd-wrong.cmake

@@ -0,0 +1,21 @@
+set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
+  "01234567-0123-0123-0123-0123456789ab")
+
+cmake_language(GET_EXPERIMENTAL_FEATURE_ENABLED
+  "CxxImportStd"
+  feature_present)
+
+if (NOT feature_present STREQUAL "FALSE")
+  message(FATAL_ERROR
+    "Expected the `CxxImportStd` feature to be disabled.")
+endif ()
+
+# Test if/when warning is repeated.
+cmake_language(GET_EXPERIMENTAL_FEATURE_ENABLED
+  "CxxImportStd"
+  feature_present)
+set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD
+  "76543210-3210-3210-3210-ba9876543210")
+cmake_language(GET_EXPERIMENTAL_FEATURE_ENABLED
+  "CxxImportStd"
+  feature_present)

Tests/RunCMake/cmake_language/Experimental/ExportPackageDependencies-wrong-stderr.txt

@@ -0,0 +1,25 @@
+^CMake Warning \(dev\) at Experimental/ExportPackageDependencies-wrong\.cmake:4 \(cmake_language\):
+  CMAKE_EXPERIMENTAL_EXPORT_PACKAGE_DEPENDENCIES is set to incorrect value
+
+    01234567-0123-0123-0123-0123456789ab
+
+  See 'Help/dev/experimental\.rst' in the source tree of this version of CMake
+  for documentation of the experimental feature and the corresponding
+  activation value\.  This project's code may require changes to work with
+  this CMake's version of the feature\.
+Call Stack \(most recent call first\):
+  CMakeLists\.txt:[0-9]+ \(include\)
+This warning is for project developers\.  Use -Wno-dev to suppress it\.
++
+CMake Warning \(dev\) at Experimental/ExportPackageDependencies-wrong\.cmake:19 \(cmake_language\):
+  CMAKE_EXPERIMENTAL_EXPORT_PACKAGE_DEPENDENCIES is set to incorrect value
+
+    76543210-3210-3210-3210-ba9876543210
+
+  See 'Help/dev/experimental\.rst' in the source tree of this version of CMake
+  for documentation of the experimental feature and the corresponding
+  activation value\.  This project's code may require changes to work with
+  this CMake's version of the feature\.
+Call Stack \(most recent call first\):
+  CMakeLists\.txt:[0-9]+ \(include\)
+This warning is for project developers\.  Use -Wno-dev to suppress it\.$

Tests/RunCMake/cmake_language/Experimental/ExportPackageDependencies-wrong.cmake

@@ -0,0 +1,21 @@
+set(CMAKE_EXPERIMENTAL_EXPORT_PACKAGE_DEPENDENCIES
+  "01234567-0123-0123-0123-0123456789ab")
+
+cmake_language(GET_EXPERIMENTAL_FEATURE_ENABLED
+  "ExportPackageDependencies"
+  feature_present)
+
+if (NOT feature_present STREQUAL "FALSE")
+  message(FATAL_ERROR
+    "Expected the `ExportPackageDependencies` feature to be disabled.")
+endif ()
+
+# Test if/when warning is repeated.
+cmake_language(GET_EXPERIMENTAL_FEATURE_ENABLED
+  "ExportPackageDependencies"
+  feature_present)
+set(CMAKE_EXPERIMENTAL_EXPORT_PACKAGE_DEPENDENCIES
+  "76543210-3210-3210-3210-ba9876543210")
+cmake_language(GET_EXPERIMENTAL_FEATURE_ENABLED
+  "ExportPackageDependencies"
+  feature_present)

Tests/RunCMake/cmake_language/Experimental/WindowsKernelModeDriver-wrong-stderr.txt

@@ -0,0 +1,25 @@
+^CMake Warning \(dev\) at Experimental/WindowsKernelModeDriver-wrong\.cmake:4 \(cmake_language\):
+  CMAKE_EXPERIMENTAL_WINDOWS_KERNEL_MODE_DRIVER is set to incorrect value
+
+    01234567-0123-0123-0123-0123456789ab
+
+  See 'Help/dev/experimental\.rst' in the source tree of this version of CMake
+  for documentation of the experimental feature and the corresponding
+  activation value\.  This project's code may require changes to work with
+  this CMake's version of the feature\.
+Call Stack \(most recent call first\):
+  CMakeLists\.txt:[0-9]+ \(include\)
+This warning is for project developers\.  Use -Wno-dev to suppress it\.
++
+CMake Warning \(dev\) at Experimental/WindowsKernelModeDriver-wrong\.cmake:19 \(cmake_language\):
+  CMAKE_EXPERIMENTAL_WINDOWS_KERNEL_MODE_DRIVER is set to incorrect value
+
+    76543210-3210-3210-3210-ba9876543210
+
+  See 'Help/dev/experimental\.rst' in the source tree of this version of CMake
+  for documentation of the experimental feature and the corresponding
+  activation value\.  This project's code may require changes to work with
+  this CMake's version of the feature\.
+Call Stack \(most recent call first\):
+  CMakeLists\.txt:[0-9]+ \(include\)
+This warning is for project developers\.  Use -Wno-dev to suppress it\.$

Tests/RunCMake/cmake_language/Experimental/WindowsKernelModeDriver-wrong.cmake

@@ -0,0 +1,21 @@
+set(CMAKE_EXPERIMENTAL_WINDOWS_KERNEL_MODE_DRIVER
+  "01234567-0123-0123-0123-0123456789ab")
+
+cmake_language(GET_EXPERIMENTAL_FEATURE_ENABLED
+  "WindowsKernelModeDriver"
+  feature_present)
+
+if (NOT feature_present STREQUAL "FALSE")
+  message(FATAL_ERROR
+    "Expected the `WindowsKernelModeDriver` feature to be disabled.")
+endif ()
+
+# Test if/when warning is repeated.
+cmake_language(GET_EXPERIMENTAL_FEATURE_ENABLED
+  "WindowsKernelModeDriver"
+  feature_present)
+set(CMAKE_EXPERIMENTAL_WINDOWS_KERNEL_MODE_DRIVER
+  "76543210-3210-3210-3210-ba9876543210")
+cmake_language(GET_EXPERIMENTAL_FEATURE_ENABLED
+  "WindowsKernelModeDriver"
+  feature_present)

Tests/RunCMake/cmake_language/RunCMakeTest.cmake

@@ -159,8 +159,11 @@ run_cmake_command(
 
 run_cmake(Experimental/CxxImportStd-set)
 run_cmake(Experimental/CxxImportStd-unset)
+run_cmake(Experimental/CxxImportStd-wrong)
 run_cmake(Experimental/ExportPackageDependencies-set)
 run_cmake(Experimental/ExportPackageDependencies-unset)
+run_cmake(Experimental/ExportPackageDependencies-wrong)
 run_cmake(Experimental/WindowsKernelModeDriver-set)
 run_cmake(Experimental/WindowsKernelModeDriver-unset)
+run_cmake(Experimental/WindowsKernelModeDriver-wrong)
 run_cmake(Experimental/Unknown)