cmMakefile: Fix @CMAKE_CURRENT_LIST_LINE@ for ExpandVariablesInStringNew

Added check for variable name in @@ evaluation and test for
configuring @CMAKE_CURRENT_LIST_LINE@ with new CMP0053

Fixes: #18646

Source/cmMakefile.cxx

@@ -2727,6 +2727,7 @@ cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
 
   cmState* state = this->GetCMakeInstance()->GetState();
 
+  static const std::string lineVar = "CMAKE_CURRENT_LIST_LINE";
   do {
     char inc = *in;
     switch (inc) {
@@ -2739,7 +2740,6 @@ cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
           const char* value = nullptr;
           std::string varresult;
           std::string svalue;
-          static const std::string lineVar = "CMAKE_CURRENT_LIST_LINE";
           switch (var.domain) {
             case NORMAL:
               if (filename && lookup == lineVar) {
@@ -2889,7 +2889,14 @@ cmake::MessageType cmMakefile::ExpandVariablesInStringNew(
                          "abcdefghijklmnopqrstuvwxyz"
                          "0123456789/_.+-")) {
             std::string variable(in + 1, nextAt - in - 1);
-            std::string varresult = this->GetSafeDefinition(variable);
+
+            std::string varresult;
+            if (filename && variable == lineVar) {
+              varresult = std::to_string(line);
+            } else {
+              varresult = this->GetSafeDefinition(variable);
+            }
+
             if (escapeQuotes) {
               varresult = cmSystemTools::EscapeQuotes(varresult);
             }

Tests/CMakeTests/StringTest.cmake.in

@@ -81,7 +81,7 @@ check_cmake_test(String
 # Execute each test listed in StringTestScript.cmake:
 #
 set(scriptname "@CMAKE_CURRENT_SOURCE_DIR@/StringTestScript.cmake")
-set(number_of_tests_expected 73)
+set(number_of_tests_expected 74)
 
 include("@CMAKE_CURRENT_SOURCE_DIR@/ExecuteScriptTests.cmake")
 execute_all_script_tests(${scriptname} number_of_tests_executed)

Tests/CMakeTests/StringTestScript.cmake

@@ -54,6 +54,9 @@ elseif(testname STREQUAL configure_line_number_CMP0053_new) # pass
 elseif(testname STREQUAL configure_line_number_CMP0053_old_use_at) # pass
   test_configure_line_number("\@CMAKE_CURRENT_LIST_LINE\@" OLD)
 
+elseif(testname STREQUAL configure_line_number_CMP0053_new_use_at) # pass
+  test_configure_line_number("\@CMAKE_CURRENT_LIST_LINE\@" NEW)
+
 elseif(testname STREQUAL configure_bogus) # fail
   string(CONFIGURE "this is @testname@" v ESCAPE_QUOTES BOGUS)