COMPILE_WARNING_AS_ERROR: Add command-line option

Add command-line option `--compile-no-warning-as-error` to ignore value of
`COMPILE_WARNING_AS_ERROR`.

Issue: #19085

Help/manual/cmake.1.rst

@@ -426,6 +426,11 @@ Options
  in :variable:`CMAKE_SOURCE_DIR` and :variable:`CMAKE_BINARY_DIR`.
  This flag tells CMake to warn about other files as well.
 
+``--compile-no-warning-as-error``
+ Ignore target property :prop_tgt:`COMPILE_WARNING_AS_ERROR` and variable
+ :variable:`CMAKE_COMPILE_WARNING_AS_ERROR`, preventing warnings from being
+ treated as errors on compile.
+
 ``--profiling-output=<path>``
  Used in conjunction with ``--profiling-format`` to output to a given path.
 

Help/release/dev/werror-property.rst

@@ -6,3 +6,8 @@ werror-property
   Target Property. If :prop_tgt:`COMPILE_WARNING_AS_ERROR` is true, it expands
   to a different flag depending on the compiler such that any warnings at
   compile will be treated as errors.
+
+* :manual:`cmake(1)` gained the command-line option
+  ``--compile-no-warning-as-error`` which causes the values of
+  the :prop_tgt:`COMPILE_WARNING_AS_ERROR` target property and
+  :variable:`CMAKE_COMPILE_WARNING_AS_ERROR` variable to be ignored.

Source/cmLocalGenerator.cxx

@@ -1026,11 +1026,13 @@ void cmLocalGenerator::AddCompileOptions(std::vector<BT<std::string>>& flags,
   }
 
   // Add Warning as errors flags
-  const cmValue wError = target->GetProperty("COMPILE_WARNING_AS_ERROR");
-  const cmValue wErrorFlag = this->Makefile->GetDefinition(
-    cmStrCat("CMAKE_", lang, "_COMPILE_OPTIONS_WARNING_AS_ERROR"));
-  if (wError.IsOn() && wErrorFlag.IsSet()) {
-    flags.emplace_back(wErrorFlag);
+  if (!this->GetCMakeInstance()->GetIgnoreWarningAsError()) {
+    const cmValue wError = target->GetProperty("COMPILE_WARNING_AS_ERROR");
+    const cmValue wErrorFlag = this->Makefile->GetDefinition(
+      cmStrCat("CMAKE_", lang, "_COMPILE_OPTIONS_WARNING_AS_ERROR"));
+    if (wError.IsOn() && wErrorFlag.IsSet()) {
+      flags.emplace_back(wErrorFlag);
+    }
   }
 
   // Add compile flag for the MSVC compiler only.

Source/cmake.cxx

@@ -1092,6 +1092,14 @@ void cmake::SetArgs(const std::vector<std::string>& args)
                   << "uninitialized variables.\n";
         state->SetCheckSystemVars(true);
         return true;
+      } },
+    CommandArgument{
+      "--compile-no-warning-as-error", CommandArgument::Values::Zero,
+      [](std::string const&, cmake* state) -> bool {
+        std::cout << "Ignoring COMPILE_WARNING_AS_ERROR target property and "
+                  << "CMAKE_COMPILE_WARNING_AS_ERROR variable.\n";
+        state->SetIgnoreWarningAsError(true);
+        return true;
       } }
   };
 

Source/cmake.h

@@ -534,6 +534,8 @@ public:
   void SetWarnUnusedCli(bool b) { this->WarnUnusedCli = b; }
   bool GetCheckSystemVars() const { return this->CheckSystemVars; }
   void SetCheckSystemVars(bool b) { this->CheckSystemVars = b; }
+  bool GetIgnoreWarningAsError() const { return this->IgnoreWarningAsError; }
+  void SetIgnoreWarningAsError(bool b) { this->IgnoreWarningAsError = b; }
 
   void MarkCliAsUsed(const std::string& variable);
 
@@ -686,6 +688,7 @@ private:
   bool WarnUninitialized = false;
   bool WarnUnusedCli = true;
   bool CheckSystemVars = false;
+  bool IgnoreWarningAsError = false;
   std::map<std::string, bool> UsedCliVariables;
   std::string CMakeEditCommand;
   std::string CXXEnvironment;

Source/cmakemain.cxx

@@ -110,6 +110,9 @@ const char* cmDocumentationOptions[][2] = {
   { "--check-system-vars",
     "Find problems with variable usage in system "
     "files." },
+  { "--compile-no-warning-as-error",
+    "Ignore COMPILE_WARNING_AS_ERROR property and "
+    "CMAKE_COMPILE_WARNING_AS_ERROR variable." },
 #  if !defined(CMAKE_BOOTSTRAP)
   { "--profiling-format=<fmt>",
     "Output data for profiling CMake scripts. Supported formats: "

Tests/RunCMake/CompileWarningAsError/RunCMakeTest.cmake

@@ -3,10 +3,11 @@ include(RunCMake)
 function(run_compile_warn test)
   set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/${test}-build)
   set(RunCMake_TEST_OUTPUT_MERGE 1)
-  run_cmake(${test})
+  run_cmake_with_options(${test} ${ARGN})
   set(RunCMake_TEST_NO_CLEAN 1)
   run_cmake_command(${test}-Build ${CMAKE_COMMAND} --build . ${verbose_args})
 endfunction()
 
 run_compile_warn(WerrorOn)
 run_compile_warn(WerrorOff)
+run_compile_warn(WerrorOnIgnore "--compile-no-warning-as-error")

Tests/RunCMake/CompileWarningAsError/WerrorOnIgnore.cmake

@@ -0,0 +1,8 @@
+enable_language(CXX)
+
+include(WarningAsErrorOptions.cmake)
+get_warning_options(warning_options)
+
+add_executable(WerrorOn warn.cxx)
+target_compile_options(WerrorOn PUBLIC "${warning_options}")
+set_target_properties(WerrorOn PROPERTIES COMPILE_WARNING_AS_ERROR ON)