Add genex support to TEST_LAUNCHER and CROSSCOMPILING_EMULATOR

Evaluate generator expressions in these properties, as they apply to
`add_test`, `add_custom_command`, and `add_custom_target`.

The `CMAKE_CROSSCOMPILING_EMULATOR` variable's `try_run` behavior occurs
at configure time and so cannot support generator expressions.

3 files changed, 32 insertions, 15 deletions

diff --git a/Source/cmCustomCommandGenerator.cxx b/Source/cmCustomCommandGenerator.cxx
index 634b63b..2dea338 100644
--- a/Source/cmCustomCommandGenerator.cxx
+++ b/Source/cmCustomCommandGenerator.cxx
@@ -284,8 +284,12 @@ void cmCustomCommandGenerator::FillEmulatorsWithArguments()
   if (!this->LG->GetMakefile()->IsOn("CMAKE_CROSSCOMPILING")) {
     return;
   }
+  cmGeneratorExpression ge(*this->LG->GetCMakeInstance(),
+                           this->CC->GetBacktrace());
 
   for (unsigned int c = 0; c < this->GetNumberOfCommands(); ++c) {
+    // If the command is the plain name of an executable target,
+    // launch it with its emulator.
     std::string const& argv0 = this->CommandLines[c][0];
     cmGeneratorTarget* target = this->LG->FindGeneratorTargetToUse(argv0);
     if (target && target->GetType() == cmStateEnums::EXECUTABLE &&
@@ -297,7 +301,12 @@ void cmCustomCommandGenerator::FillEmulatorsWithArguments()
         continue;
       }
 
-      cmExpandList(*emulator_property, this->EmulatorsWithArguments[c]);
+      // Plain target names are replaced by GetArgv0Location with the
+      // path to the executable artifact in the command config, so
+      // evaluate the launcher's location in the command config too.
+      std::string const emulator =
+        ge.Parse(*emulator_property)->Evaluate(this->LG, this->CommandConfig);
+      cmExpandList(emulator, this->EmulatorsWithArguments[c]);
     }
   }
 }
@@ -313,6 +322,8 @@ std::vector<std::string> cmCustomCommandGenerator::GetCrossCompilingEmulator(
 
 const char* cmCustomCommandGenerator::GetArgv0Location(unsigned int c) const
 {
+  // If the command is the plain name of an executable target, we replace it
+  // with the path to the executable artifact in the command config.
   std::string const& argv0 = this->CommandLines[c][0];
   cmGeneratorTarget* target = this->LG->FindGeneratorTargetToUse(argv0);
   if (target && target->GetType() == cmStateEnums::EXECUTABLE &&
diff --git a/Source/cmFileAPICodemodel.cxx b/Source/cmFileAPICodemodel.cxx
index 30a7e67..e9302da 100644
--- a/Source/cmFileAPICodemodel.cxx
+++ b/Source/cmFileAPICodemodel.cxx
@@ -2092,18 +2092,22 @@ Json::Value Target::DumpLauncher(const char* name, const char* type)
   cmValue property = this->GT->GetProperty(name);
   Json::Value launcher;
   if (property) {
-    cmList commandWithArgs{ *property };
-    std::string command(commandWithArgs[0]);
-    cmSystemTools::ConvertToUnixSlashes(command);
-    launcher = Json::objectValue;
-    launcher["command"] = RelativeIfUnder(this->TopSource, command);
-    launcher["type"] = type;
-    Json::Value args;
-    for (std::string const& arg : cmMakeRange(commandWithArgs).advance(1)) {
-      args.append(arg);
-    }
-    if (!args.empty()) {
-      launcher["arguments"] = std::move(args);
+    cmLocalGenerator* lg = this->GT->GetLocalGenerator();
+    cmGeneratorExpression ge(*lg->GetCMakeInstance());
+    cmList commandWithArgs{ ge.Parse(*property)->Evaluate(lg, this->Config) };
+    if (!commandWithArgs.empty() && !commandWithArgs[0].empty()) {
+      std::string command(commandWithArgs[0]);
+      cmSystemTools::ConvertToUnixSlashes(command);
+      launcher = Json::objectValue;
+      launcher["command"] = RelativeIfUnder(this->TopSource, command);
+      launcher["type"] = type;
+      Json::Value args;
+      for (std::string const& arg : cmMakeRange(commandWithArgs).advance(1)) {
+        args.append(arg);
+      }
+      if (!args.empty()) {
+        launcher["arguments"] = std::move(args);
+      }
     }
   }
   return launcher;
diff --git a/Source/cmTestGenerator.cxx b/Source/cmTestGenerator.cxx
index f7403cf..840d8cf 100644
--- a/Source/cmTestGenerator.cxx
+++ b/Source/cmTestGenerator.cxx
@@ -168,12 +168,14 @@ void cmTestGenerator::GenerateScriptForConfig(std::ostream& os,
     // Use the target file on disk.
     exe = target->GetFullPath(config);
 
-    auto addLauncher = [&os, target](std::string const& propertyName) {
+    auto addLauncher = [this, &config, &ge, &os,
+                        target](std::string const& propertyName) {
       cmValue launcher = target->GetProperty(propertyName);
       if (!cmNonempty(launcher)) {
         return;
       }
-      cmList launcherWithArgs{ *launcher };
+      cmList launcherWithArgs{ ge.Parse(*launcher)->Evaluate(this->LG,
+                                                             config) };
       if (!launcherWithArgs.empty() && !launcherWithArgs[0].empty()) {
         std::string launcherExe(launcherWithArgs[0]);
         cmSystemTools::ConvertToUnixSlashes(launcherExe);