Ninja Multi-Config: Fix custom command target dependencies in cross-configs

Generator expressions in a non-cross custom command's `COMMAND`
arguments are evaluated in the command config.  Target-level
dependencies implied by `TARGET_FILE` must therefore be cross
dependencies.  This is important to generate proper target-level
dependencies on the cross-config build statements for the target to
which the custom command is attached.

Fixes: #22855

Source/cmCustomCommandGenerator.cxx

@@ -91,7 +91,7 @@ std::string EvaluateSplitConfigGenex(
 
     // Record targets referenced by the genex.
     if (utils) {
-      // FIXME: What is the proper condition for a cross-dependency?
+      // Use a cross-dependency if we referenced the command config.
       bool const cross = !useOutputConfig;
       for (cmGeneratorTarget* gt : cge->GetTargets()) {
         utils->emplace(BT<std::pair<std::string, bool>>(
@@ -176,6 +176,8 @@ cmCustomCommandGenerator::cmCustomCommandGenerator(
   cmGeneratorTarget const* target{ lg->FindGeneratorTargetToUse(
     this->Target) };
 
+  bool const distinctConfigs = this->OutputConfig != this->CommandConfig;
+
   const cmCustomCommandLines& cmdlines = this->CC->GetCommandLines();
   for (cmCustomCommandLine const& cmdline : cmdlines) {
     cmCustomCommandLine argv;
@@ -191,16 +193,18 @@ cmCustomCommandGenerator::cmCustomCommandGenerator(
         argv.push_back(std::move(parsed_arg));
       }
 
+      if (distinctConfigs) {
         // For remaining arguments, we default to the OUTPUT_CONFIG.
         useOutputConfig = true;
       }
+    }
 
     if (!argv.empty()) {
       // If the command references an executable target by name,
       // collect the target to add a target-level dependency on it.
       cmGeneratorTarget* gt = this->LG->FindGeneratorTargetToUse(argv.front());
       if (gt && gt->GetType() == cmStateEnums::EXECUTABLE) {
-        // FIXME: What is the proper condition for a cross-dependency?
+        // GetArgv0Location uses the command config, so use a cross-dependency.
         bool const cross = true;
         this->Utilities.emplace(BT<std::pair<std::string, bool>>(
           { gt->GetName(), cross }, cc.GetBacktrace()));

Tests/RunCMake/NinjaMultiConfig/CustomCommandOutputGenex-echo_depend_target-debug-in-release-graph-ninja-stdout.txt

@@ -0,0 +1,2 @@
+^\[1/1\] Generating echo_depend_target\.txt
+'[^']*[\/]Tests[\/]RunCMake[\/]NinjaMultiConfig[\/]CustomCommandOutputGenex-build'\$ '[^']*[\/]Tests[\/]RunCMake[\/]NinjaMultiConfig[\/]CustomCommandOutputGenex-build[\/]Release[\/]echo(\.exe)?' 'Release'$

Tests/RunCMake/NinjaMultiConfig/CustomCommandOutputGenex-echo_depend_target-debug-ninja-stdout.txt

@@ -0,0 +1,2 @@
+^\[1/1\] Generating echo_depend_target\.txt
+'[^']*[\/]Tests[\/]RunCMake[\/]NinjaMultiConfig[\/]CustomCommandOutputGenex-build'\$ '[^']*[\/]Tests[\/]RunCMake[\/]NinjaMultiConfig[\/]CustomCommandOutputGenex-build[\/]Debug[\/]echo(\.exe)?' 'Debug'$

Tests/RunCMake/NinjaMultiConfig/CustomCommandOutputGenex-echo_depend_target-release-ninja-stdout.txt

@@ -0,0 +1,2 @@
+^\[1/1\] Generating echo_depend_target\.txt
+'[^']*[\/]Tests[\/]RunCMake[\/]NinjaMultiConfig[\/]CustomCommandOutputGenex-build'\$ '[^']*[\/]Tests[\/]RunCMake[\/]NinjaMultiConfig[\/]CustomCommandOutputGenex-build[\/]Release[\/]echo(\.exe)?' 'Release'$

Tests/RunCMake/NinjaMultiConfig/CustomCommandOutputGenex.cmake

@@ -143,6 +143,16 @@ add_custom_command(
     PROPERTY SYMBOLIC 1)
 add_custom_target(echo_dbgx DEPENDS "$<$<CONFIG:Debug>:echo_dbgx_Debug.txt>")
 
+# A non-cross-config custom command expresses target dependencies in command config.
+add_custom_command(
+  OUTPUT echo_depend_target.txt
+  COMMAND ${CMAKE_COMMAND} -E env $<TARGET_FILE:echo> $<CONFIG>
+  # A real project should do:
+  #   DEPENDS $<TARGET_FILE:echo>
+  # but here we are testing the target-level dependency implied by TARGET_FILE.
+  )
+add_custom_target(echo_depend_target DEPENDS echo_depend_target.txt)
+
 add_custom_target(echo_target_raw
   BYPRODUCTS echo_target_raw_$<CONFIG>.txt
   COMMENT echo_target_raw

Tests/RunCMake/NinjaMultiConfig/RunCMakeTest.cmake

@@ -344,6 +344,16 @@ run_ninja(CustomCommandOutputGenex echo_dbgx-release build-Release.ninja echo_db
 run_ninja(CustomCommandOutputGenex clean-release-graph build-Release.ninja -t clean)
 run_ninja(CustomCommandOutputGenex echo_dbgx-debug-in-release-graph build-Release.ninja echo_dbgx:Debug)
 run_ninja(CustomCommandOutputGenex clean-release-graph build-Release.ninja -t clean)
+# echo_depend_target
+run_ninja(CustomCommandOutputGenex echo_depend_target-debug-prep build-Debug.ninja echo:Debug)
+run_ninja(CustomCommandOutputGenex echo_depend_target-debug build-Debug.ninja echo_depend_target)
+run_ninja(CustomCommandOutputGenex clean-debug-graph build-Debug.ninja -t clean)
+run_ninja(CustomCommandOutputGenex echo_depend_target-release-prep build-Release.ninja echo:Release)
+run_ninja(CustomCommandOutputGenex echo_depend_target-release build-Release.ninja echo_depend_target)
+run_ninja(CustomCommandOutputGenex clean-release-graph build-Release.ninja -t clean)
+run_ninja(CustomCommandOutputGenex echo_depend_target-debug-in-release-graph-prep build-Release.ninja echo:Release)
+run_ninja(CustomCommandOutputGenex echo_depend_target-debug-in-release-graph build-Release.ninja echo_depend_target:Debug)
+run_ninja(CustomCommandOutputGenex clean-release-graph build-Release.ninja -t clean)
 # echo_target_raw
 run_ninja(CustomCommandOutputGenex echo_target_raw-debug build-Debug.ninja echo_target_raw:Debug)
 run_ninja(CustomCommandOutputGenex clean-debug-graph build-Debug.ninja -t clean)