tests: test CMP0053 in WARN mode when watching variables

When CMP0053 is in WARN mode, variables get expanded twice, leaking the
fact that the string was expanded twice and changing behavior. Instead,
suppress variable watches when running the expansion to trigger the
CMP0053 warning.

Source/cmMakefile.cxx

@@ -103,6 +103,7 @@ cmMakefile::cmMakefile(): Internal(new Internals)
   this->GeneratingBuildSystem = false;
 
   this->NumLastMatches = 0;
+  this->SuppressWatches = false;
 }
 
 cmMakefile::cmMakefile(const cmMakefile& mf): Internal(new Internals)
@@ -153,6 +154,7 @@ cmMakefile::cmMakefile(const cmMakefile& mf): Internal(new Internals)
   this->OutputToSource = mf.OutputToSource;
 
   this->NumLastMatches = mf.NumLastMatches;
+  this->SuppressWatches = mf.SuppressWatches;
 }
 
 //----------------------------------------------------------------------------
@@ -2463,7 +2465,7 @@ const char* cmMakefile::GetDefinition(const std::string& name) const
     }
 #ifdef CMAKE_BUILD_WITH_CMAKE
   cmVariableWatch* vv = this->GetVariableWatch();
-  if ( vv )
+  if ( vv && !this->SuppressWatches )
     {
     if ( def )
       {
@@ -2570,10 +2572,14 @@ const char *cmMakefile::ExpandVariablesInString(std::string& source,
       original = source;
       newResult = source;
       compareResults = true;
+      // Suppress variable watches to avoid calling hooks twice. Suppress new
+      // dereferences since the OLD behavior is still what is actually used.
+      this->SuppressWatches = true;
       newError =
         ExpandVariablesInStringNew(newErrorstr, newResult, escapeQuotes,
                                    noEscapes, atOnly, filename, line,
                                    removeEmpty, replaceAt);
+      this->SuppressWatches = false;
       }
     case cmPolicies::OLD:
       mtype = ExpandVariablesInStringOld(errorstr, source, escapeQuotes,

Source/cmMakefile.h

@@ -1127,6 +1127,8 @@ private:
                              const std::string& feature) const;
   bool HaveCxxFeatureAvailable(cmTarget const* target,
                                const std::string& feature) const;
+
+  mutable bool SuppressWatches;
 };
 
 //----------------------------------------------------------------------------

Tests/RunCMake/CMP0053/CMP0053-NEW-stderr.txt

@@ -0,0 +1,2 @@
+^called
+--><--$

Tests/RunCMake/CMP0053/CMP0053-NEW.cmake

@@ -0,0 +1,8 @@
+cmake_policy(SET CMP0053 NEW)
+
+function (watch_callback)
+  message("called")
+endfunction ()
+
+variable_watch(test watch_callback)
+message("-->${test}<--")

Tests/RunCMake/CMP0053/CMP0053-OLD-stderr.txt

@@ -0,0 +1,2 @@
+^called
+--><--$

Tests/RunCMake/CMP0053/CMP0053-OLD.cmake

@@ -0,0 +1,8 @@
+cmake_policy(SET CMP0053 OLD)
+
+function (watch_callback)
+  message("called")
+endfunction ()
+
+variable_watch(test watch_callback)
+message("-->${test}<--")

Tests/RunCMake/CMP0053/CMP0053-WARN-stderr.txt

@@ -0,0 +1,2 @@
+^called
+--><--$

Tests/RunCMake/CMP0053/CMP0053-WARN.cmake

@@ -0,0 +1,6 @@
+function (watch_callback)
+  message("called")
+endfunction ()
+
+variable_watch(test watch_callback)
+message("-->${test}<--")

Tests/RunCMake/CMP0053/CMakeLists.txt

@@ -0,0 +1,3 @@
+cmake_minimum_required(VERSION 3.0)
+project(${RunCMake_TEST} CXX)
+include(${RunCMake_TEST}.cmake)

Tests/RunCMake/CMP0053/RunCMakeTest.cmake

@@ -0,0 +1,5 @@
+include(RunCMake)
+
+run_cmake(CMP0053-OLD)
+run_cmake(CMP0053-NEW)
+run_cmake(CMP0053-WARN)

Tests/RunCMake/CMakeLists.txt

@@ -35,6 +35,7 @@ add_RunCMake_test(CMP0046)
 add_RunCMake_test(CMP0049)
 add_RunCMake_test(CMP0050)
 add_RunCMake_test(CMP0051)
+add_RunCMake_test(CMP0053)
 add_RunCMake_test(CTest)
 if(UNIX AND "${CMAKE_GENERATOR}" MATCHES "Unix Makefiles")
   add_RunCMake_test(CompilerChange)