Add cmake_language(GET_MESSAGE_LOG_LEVEL) sub command

The new sub-command writes a string representation of the
current log level to the output variable given to the
sub-command.

Given that the log-level might be set either via the --log-level
command line option or via the CMAKE_MESSAGE_LOG_LEVEL
cache / regular variables, the priority for each of the log level
sources is as follows, with the first one being the highest:
1) --log-level
2) CMAKE_MESSAGE_LOG_LEVEL regular variable
3) CMAKE_MESSAGE_LOG_LEVEL cache variable
4) default log level (STATUS)

Fixes: #23572

19 files changed, 205 insertions, 25 deletions

diff --git a/Help/command/cmake_language.rst b/Help/command/cmake_language.rst
index cb8d60b..377e42d 100644
--- a/Help/command/cmake_language.rst
+++ b/Help/command/cmake_language.rst
@@ -14,6 +14,7 @@ Synopsis
   cmake_language(`EVAL`_ CODE <code>...)
   cmake_language(`DEFER`_ <options>... CALL <command> [<arg>...])
   cmake_language(`SET_DEPENDENCY_PROVIDER`_ <command> SUPPORTED_METHODS <methods>...)
+  cmake_language(`GET_MESSAGE_LOG_LEVEL`_ <out-var>)
 
 Introduction
 ^^^^^^^^^^^^
@@ -491,3 +492,28 @@ calling the provider command recursively for the same dependency.
     SET_DEPENDENCY_PROVIDER mycomp_provide_dependency
     SUPPORTED_METHODS FIND_PACKAGE
   )
+
+Getting current message log level
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. versionadded:: 3.25
+
+.. _GET_MESSAGE_LOG_LEVEL:
+.. _query_message_log_level:
+
+.. code-block:: cmake
+
+  cmake_language(GET_MESSAGE_LOG_LEVEL <output_variable>)
+
+Writes the current :command:`message` logging level
+into the given ``<output_variable>``.
+
+See :command:`message` for the possible logging levels.
+
+The current message logging level can be set either using the ``--log-level``
+command line option of the :manual:`cmake(1)` program or using
+the :variable:`CMAKE_MESSAGE_LOG_LEVEL` variable.
+
+If both the command line option and the variable are set, the command line
+option takes precedence. If neither are set, the default logging level
+is returned.
diff --git a/Help/manual/cmake.1.rst b/Help/manual/cmake.1.rst
index 38105dd..2726f13 100644
--- a/Help/manual/cmake.1.rst
+++ b/Help/manual/cmake.1.rst
@@ -249,6 +249,11 @@ Options
  For backward compatibility reasons, ``--loglevel`` is also accepted as a
  synonym for this option.
 
+ .. versionadded:: 3.25
+   See the :command:`cmake_language`
+   :ref:`cmake_language <query_message_log_level>` command for a way to query
+   the current message logging level.
+
 ``--log-context``
  Enable the :command:`message` command outputting context attached to each
  message.
diff --git a/Help/release/dev/cmake_language_GET_MESSAGE_LOG_LEVEL.rst b/Help/release/dev/cmake_language_GET_MESSAGE_LOG_LEVEL.rst
new file mode 100644
index 0000000..6e99a05
--- /dev/null
+++ b/Help/release/dev/cmake_language_GET_MESSAGE_LOG_LEVEL.rst
@@ -0,0 +1,6 @@
+cmake-language_GET_MESSAGE_LOG_LEVEL
+------------------------------------
+
+* The :command:`cmake_language` command gained a new
+  ``GET_MESSAGE_LOG_LEVEL`` sub-command.  It can be used to
+  query the current message logging level.
diff --git a/Help/variable/CMAKE_MESSAGE_LOG_LEVEL.rst b/Help/variable/CMAKE_MESSAGE_LOG_LEVEL.rst
index 3b45d1d..54ea6a4 100644
--- a/Help/variable/CMAKE_MESSAGE_LOG_LEVEL.rst
+++ b/Help/variable/CMAKE_MESSAGE_LOG_LEVEL.rst
@@ -15,3 +15,8 @@ subsequent CMake runs will continue to use the chosen log level.
 
 Projects should not set this variable, it is intended for users so that
 they may control the log level according to their own needs.
+
+.. versionadded:: 3.25
+  See the :command:`cmake_language`
+  :ref:`cmake_language <query_message_log_level>` command for a way to query
+  the current message logging level.
diff --git a/Source/cmCMakeLanguageCommand.cxx b/Source/cmCMakeLanguageCommand.cxx
index a2aaa2a..287f45b 100644
--- a/Source/cmCMakeLanguageCommand.cxx
+++ b/Source/cmCMakeLanguageCommand.cxx
@@ -19,10 +19,12 @@
 #include "cmGlobalGenerator.h"
 #include "cmListFileCache.h"
 #include "cmMakefile.h"
+#include "cmMessageType.h"
 #include "cmRange.h"
 #include "cmState.h"
 #include "cmStringAlgorithms.h"
 #include "cmSystemTools.h"
+#include "cmake.h"
 
 namespace {
 
@@ -303,6 +305,27 @@ bool cmCMakeLanguageCommandSET_DEPENDENCY_PROVIDER(
 
   return true;
 }
+
+bool cmCMakeLanguageCommandGET_MESSAGE_LOG_LEVEL(
+  std::vector<cmListFileArgument> const& args, cmExecutionStatus& status)
+{
+  cmMakefile& makefile = status.GetMakefile();
+  std::vector<std::string> expandedArgs;
+  makefile.ExpandArguments(args, expandedArgs);
+
+  if (args.size() < 2 || expandedArgs.size() > 2) {
+    return FatalError(
+      status,
+      "sub-command GET_MESSAGE_LOG_LEVEL expects exactly one argument");
+  }
+
+  Message::LogLevel logLevel = makefile.GetCurrentLogLevel();
+  std::string outputValue = cmake::LogLevelToString(logLevel);
+
+  const std::string& outputVariable = expandedArgs[1];
+  makefile.AddDefinition(outputVariable, outputValue);
+  return true;
+}
 }
 
 bool cmCMakeLanguageCommand(std::vector<cmListFileArgument> const& args,
@@ -451,5 +474,9 @@ bool cmCMakeLanguageCommand(std::vector<cmListFileArgument> const& args,
     return cmCMakeLanguageCommandEVAL(args, status);
   }
 
+  if (expArgs[expArg] == "GET_MESSAGE_LOG_LEVEL") {
+    return cmCMakeLanguageCommandGET_MESSAGE_LOG_LEVEL(args, status);
+  }
+
   return FatalError(status, "called with unknown meta-operation");
 }
diff --git a/Source/cmMakefile.cxx b/Source/cmMakefile.cxx
index 97a3db9..62ea427 100644
--- a/Source/cmMakefile.cxx
+++ b/Source/cmMakefile.cxx
@@ -149,6 +149,29 @@ void cmMakefile::IssueMessage(MessageType t, std::string const& text) const
   this->GetCMakeInstance()->IssueMessage(t, text, this->Backtrace);
 }
 
+Message::LogLevel cmMakefile::GetCurrentLogLevel() const
+{
+  const cmake* cmakeInstance = this->GetCMakeInstance();
+
+  const Message::LogLevel logLevelCliOrDefault = cmakeInstance->GetLogLevel();
+  assert("Expected a valid log level here" &&
+         logLevelCliOrDefault != Message::LogLevel::LOG_UNDEFINED);
+
+  Message::LogLevel result = logLevelCliOrDefault;
+
+  // If the log-level was set via the command line option, it takes precedence
+  // over the CMAKE_MESSAGE_LOG_LEVEL variable.
+  if (!cmakeInstance->WasLogLevelSetViaCLI()) {
+    const Message::LogLevel logLevelFromVar = cmake::StringToLogLevel(
+      this->GetSafeDefinition("CMAKE_MESSAGE_LOG_LEVEL"));
+    if (logLevelFromVar != Message::LogLevel::LOG_UNDEFINED) {
+      result = logLevelFromVar;
+    }
+  }
+
+  return result;
+}
+
 bool cmMakefile::CheckCMP0037(std::string const& targetName,
                               cmStateEnums::TargetType targetType) const
 {
diff --git a/Source/cmMakefile.h b/Source/cmMakefile.h
index e7b9716..df40c82 100644
--- a/Source/cmMakefile.h
+++ b/Source/cmMakefile.h
@@ -925,6 +925,7 @@ public:
   };
 
   void IssueMessage(MessageType t, std::string const& text) const;
+  Message::LogLevel GetCurrentLogLevel() const;
 
   /** Set whether or not to report a CMP0000 violation.  */
   void SetCheckCMP0000(bool b) { this->CheckCMP0000 = b; }
diff --git a/Source/cmMessageCommand.cxx b/Source/cmMessageCommand.cxx
index 9628124..fa29ec9 100644
--- a/Source/cmMessageCommand.cxx
+++ b/Source/cmMessageCommand.cxx
@@ -157,18 +157,7 @@ bool cmMessageCommand(std::vector<std::string> const& args,
   assert("Message log level expected to be set" &&
          level != Message::LogLevel::LOG_UNDEFINED);
 
-  auto desiredLevel = mf.GetCMakeInstance()->GetLogLevel();
-  assert("Expected a valid log level here" &&
-         desiredLevel != Message::LogLevel::LOG_UNDEFINED);
-
-  // Command line option takes precedence over the cache variable
-  if (!mf.GetCMakeInstance()->WasLogLevelSetViaCLI()) {
-    const auto desiredLevelFromCache =
-      cmake::StringToLogLevel(mf.GetSafeDefinition("CMAKE_MESSAGE_LOG_LEVEL"));
-    if (desiredLevelFromCache != Message::LogLevel::LOG_UNDEFINED) {
-      desiredLevel = desiredLevelFromCache;
-    }
-  }
+  Message::LogLevel desiredLevel = mf.GetCurrentLogLevel();
 
   if (desiredLevel < level) {
     // Suppress the message
diff --git a/Source/cmake.cxx b/Source/cmake.cxx
index 026c3d4..efb2520 100644
--- a/Source/cmake.cxx
+++ b/Source/cmake.cxx
@@ -3,6 +3,7 @@
 #include "cmake.h"
 
 #include <algorithm>
+#include <array>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
@@ -1402,21 +1403,32 @@ void cmake::SetArgs(const std::vector<std::string>& args)
 #endif
 }
 
-Message::LogLevel cmake::StringToLogLevel(const std::string& levelStr)
-{
-  using LevelsPair = std::pair<std::string, Message::LogLevel>;
-  static const std::vector<LevelsPair> levels = {
-    { "error", Message::LogLevel::LOG_ERROR },
-    { "warning", Message::LogLevel::LOG_WARNING },
-    { "notice", Message::LogLevel::LOG_NOTICE },
-    { "status", Message::LogLevel::LOG_STATUS },
-    { "verbose", Message::LogLevel::LOG_VERBOSE },
-    { "debug", Message::LogLevel::LOG_DEBUG },
-    { "trace", Message::LogLevel::LOG_TRACE }
+namespace {
+using LevelsPair = std::pair<cm::string_view, Message::LogLevel>;
+using LevelsPairArray = std::array<LevelsPair, 7>;
+const LevelsPairArray& getStringToLogLevelPairs()
+{
+  static const LevelsPairArray levels = {
+    { { "error", Message::LogLevel::LOG_ERROR },
+      { "warning", Message::LogLevel::LOG_WARNING },
+      { "notice", Message::LogLevel::LOG_NOTICE },
+      { "status", Message::LogLevel::LOG_STATUS },
+      { "verbose", Message::LogLevel::LOG_VERBOSE },
+      { "debug", Message::LogLevel::LOG_DEBUG },
+      { "trace", Message::LogLevel::LOG_TRACE } }
   };
+  return levels;
+}
+} // namespace
+
+Message::LogLevel cmake::StringToLogLevel(cm::string_view levelStr)
+{
+  const LevelsPairArray& levels = getStringToLogLevelPairs();
 
-  const auto levelStrLowCase = cmSystemTools::LowerCase(levelStr);
+  const auto levelStrLowCase =
+    cmSystemTools::LowerCase(std::string{ levelStr });
 
+  // NOLINTNEXTLINE(readability-qualified-auto)
   const auto it = std::find_if(levels.cbegin(), levels.cend(),
                                [&levelStrLowCase](const LevelsPair& p) {
                                  return p.first == levelStrLowCase;
@@ -1424,6 +1436,21 @@ Message::LogLevel cmake::StringToLogLevel(const std::string& levelStr)
   return (it != levels.cend()) ? it->second : Message::LogLevel::LOG_UNDEFINED;
 }
 
+std::string cmake::LogLevelToString(Message::LogLevel level)
+{
+  const LevelsPairArray& levels = getStringToLogLevelPairs();
+
+  // NOLINTNEXTLINE(readability-qualified-auto)
+  const auto it =
+    std::find_if(levels.cbegin(), levels.cend(),
+                 [&level](const LevelsPair& p) { return p.second == level; });
+  const cm::string_view levelStrLowerCase =
+    (it != levels.cend()) ? it->first : "undefined";
+  std::string levelStrUpperCase =
+    cmSystemTools::UpperCase(std::string{ levelStrLowerCase });
+  return levelStrUpperCase;
+}
+
 cmake::TraceFormat cmake::StringToTraceFormat(const std::string& traceStr)
 {
   using TracePair = std::pair<std::string, TraceFormat>;
diff --git a/Source/cmake.h b/Source/cmake.h
index 9d3348d..a631647 100644
--- a/Source/cmake.h
+++ b/Source/cmake.h
@@ -458,7 +458,8 @@ public:
   //! Get the selected log level for `message()` commands during the cmake run.
   Message::LogLevel GetLogLevel() const { return this->MessageLogLevel; }
   void SetLogLevel(Message::LogLevel level) { this->MessageLogLevel = level; }
-  static Message::LogLevel StringToLogLevel(const std::string& levelStr);
+  static Message::LogLevel StringToLogLevel(cm::string_view levelStr);
+  static std::string LogLevelToString(Message::LogLevel level);
   static TraceFormat StringToTraceFormat(const std::string& levelStr);
 
   bool HasCheckInProgress() const
diff --git a/Tests/RunCMake/cmake_language/RunCMakeTest.cmake b/Tests/RunCMake/cmake_language/RunCMakeTest.cmake
index 6480b2e..03a15fc 100644
--- a/Tests/RunCMake/cmake_language/RunCMakeTest.cmake
+++ b/Tests/RunCMake/cmake_language/RunCMakeTest.cmake
@@ -82,3 +82,61 @@ run_cmake(defer_get_call_id_var)
 run_cmake(defer_missing_arg)
 run_cmake(defer_missing_call)
 run_cmake(defer_unknown_option)
+
+# Default log level
+run_cmake_command(
+    get_message_log_level_none
+    ${CMAKE_COMMAND}
+    -P ${RunCMake_SOURCE_DIR}/get_message_log_level.cmake
+  )
+
+# Log level from cache
+run_cmake_command(
+    get_message_log_level_cache
+    ${CMAKE_COMMAND}
+    -DCMAKE_MESSAGE_LOG_LEVEL=TRACE
+    -P ${RunCMake_SOURCE_DIR}/get_message_log_level.cmake
+  )
+
+# Log level from regular variable
+run_cmake_command(
+    get_message_log_level_var
+    ${CMAKE_COMMAND}
+    -DNEW_LOG_LEVEL=TRACE
+    -P ${RunCMake_SOURCE_DIR}/get_message_log_level.cmake
+  )
+
+# Log level from command line
+run_cmake_command(
+    get_message_log_level_cli
+    ${CMAKE_COMMAND}
+    --log-level=DEBUG
+    -P ${RunCMake_SOURCE_DIR}/get_message_log_level.cmake
+  )
+
+# Log level from command line, it has higher priority over a cache variable
+run_cmake_command(
+    get_message_log_level_cli_and_cache
+    ${CMAKE_COMMAND}
+    --log-level=DEBUG
+    -DCMAKE_MESSAGE_LOG_LEVEL=TRACE
+    -P ${RunCMake_SOURCE_DIR}/get_message_log_level.cmake
+  )
+
+# Log level from command line, it has higher priority over a regular variable
+run_cmake_command(
+    get_message_log_level_cli_and_var
+    ${CMAKE_COMMAND}
+    --log-level=DEBUG
+    -DNEW_LOG_LEVEL=TRACE
+    -P ${RunCMake_SOURCE_DIR}/get_message_log_level.cmake
+  )
+
+# Log level from variable, it has higher priority over a cache variable
+run_cmake_command(
+    get_message_log_level_var_and_cache
+    ${CMAKE_COMMAND}
+    -DNEW_LOG_LEVEL=DEBUG
+    -DCMAKE_MESSAGE_LOG_LEVEL=TRACE
+    -P ${RunCMake_SOURCE_DIR}/get_message_log_level.cmake
+  )
diff --git a/Tests/RunCMake/cmake_language/get_message_log_level.cmake b/Tests/RunCMake/cmake_language/get_message_log_level.cmake
new file mode 100644
index 0000000..1740c1f
--- /dev/null
+++ b/Tests/RunCMake/cmake_language/get_message_log_level.cmake
@@ -0,0 +1,5 @@
+if(NEW_LOG_LEVEL)
+    set(CMAKE_MESSAGE_LOG_LEVEL "${NEW_LOG_LEVEL}")
+endif()
+cmake_language(GET_MESSAGE_LOG_LEVEL log_level)
+message(STATUS "log level is: ${log_level}")
diff --git a/Tests/RunCMake/cmake_language/get_message_log_level_cache-stdout.txt b/Tests/RunCMake/cmake_language/get_message_log_level_cache-stdout.txt
new file mode 100644
index 0000000..cf1cd7b
--- /dev/null
+++ b/Tests/RunCMake/cmake_language/get_message_log_level_cache-stdout.txt
@@ -0,0 +1 @@
+log level is: TRACE
diff --git a/Tests/RunCMake/cmake_language/get_message_log_level_cli-stdout.txt b/Tests/RunCMake/cmake_language/get_message_log_level_cli-stdout.txt
new file mode 100644
index 0000000..4d6e1eb
--- /dev/null
+++ b/Tests/RunCMake/cmake_language/get_message_log_level_cli-stdout.txt
@@ -0,0 +1 @@
+log level is: DEBUG
diff --git a/Tests/RunCMake/cmake_language/get_message_log_level_cli_and_cache-stdout.txt b/Tests/RunCMake/cmake_language/get_message_log_level_cli_and_cache-stdout.txt
new file mode 100644
index 0000000..4d6e1eb
--- /dev/null
+++ b/Tests/RunCMake/cmake_language/get_message_log_level_cli_and_cache-stdout.txt
@@ -0,0 +1 @@
+log level is: DEBUG
diff --git a/Tests/RunCMake/cmake_language/get_message_log_level_cli_and_var-stdout.txt b/Tests/RunCMake/cmake_language/get_message_log_level_cli_and_var-stdout.txt
new file mode 100644
index 0000000..4d6e1eb
--- /dev/null
+++ b/Tests/RunCMake/cmake_language/get_message_log_level_cli_and_var-stdout.txt
@@ -0,0 +1 @@
+log level is: DEBUG
diff --git a/Tests/RunCMake/cmake_language/get_message_log_level_none-stdout.txt b/Tests/RunCMake/cmake_language/get_message_log_level_none-stdout.txt
new file mode 100644
index 0000000..92ffd34
--- /dev/null
+++ b/Tests/RunCMake/cmake_language/get_message_log_level_none-stdout.txt
@@ -0,0 +1 @@
+log level is: STATUS
diff --git a/Tests/RunCMake/cmake_language/get_message_log_level_var-stdout.txt b/Tests/RunCMake/cmake_language/get_message_log_level_var-stdout.txt
new file mode 100644
index 0000000..cf1cd7b
--- /dev/null
+++ b/Tests/RunCMake/cmake_language/get_message_log_level_var-stdout.txt
@@ -0,0 +1 @@
+log level is: TRACE
diff --git a/Tests/RunCMake/cmake_language/get_message_log_level_var_and_cache-stdout.txt b/Tests/RunCMake/cmake_language/get_message_log_level_var_and_cache-stdout.txt
new file mode 100644
index 0000000..4d6e1eb
--- /dev/null
+++ b/Tests/RunCMake/cmake_language/get_message_log_level_var_and_cache-stdout.txt
@@ -0,0 +1 @@
+log level is: DEBUG