add_custom_{command,target}: WORKING_DIRECTORY generator expressions

This teaches add_custom_command and add_custom_target WORKING_DIRECTORY
about generator expressions

Fixes: #14089

2 files changed, 9 insertions, 1 deletions

diff --git a/Source/cmCustomCommandGenerator.cxx b/Source/cmCustomCommandGenerator.cxx
index 6c9f9d6..5bbae17 100644
--- a/Source/cmCustomCommandGenerator.cxx
+++ b/Source/cmCustomCommandGenerator.cxx
@@ -64,6 +64,13 @@ cmCustomCommandGenerator::cmCustomCommandGenerator(cmCustomCommand const& cc,
     }
     this->Depends.insert(this->Depends.end(), result.begin(), result.end());
   }
+
+  const std::string& workingdirectory = this->CC.GetWorkingDirectory();
+  if (!workingdirectory.empty()) {
+    std::unique_ptr<cmCompiledGeneratorExpression> cge =
+      this->GE->Parse(workingdirectory);
+    this->WorkingDirectory = cge->Evaluate(this->LG, this->Config);
+  }
 }
 
 cmCustomCommandGenerator::~cmCustomCommandGenerator()
@@ -186,7 +193,7 @@ const char* cmCustomCommandGenerator::GetComment() const
 
 std::string cmCustomCommandGenerator::GetWorkingDirectory() const
 {
-  return this->CC.GetWorkingDirectory();
+  return this->WorkingDirectory;
 }
 
 std::vector<std::string> const& cmCustomCommandGenerator::GetOutputs() const
diff --git a/Source/cmCustomCommandGenerator.h b/Source/cmCustomCommandGenerator.h
index 34fd653..b7e2a39 100644
--- a/Source/cmCustomCommandGenerator.h
+++ b/Source/cmCustomCommandGenerator.h
@@ -23,6 +23,7 @@ class cmCustomCommandGenerator
   cmGeneratorExpression* GE;
   cmCustomCommandLines CommandLines;
   std::vector<std::string> Depends;
+  std::string WorkingDirectory;
 
   const char* GetCrossCompilingEmulator(unsigned int c) const;
   const char* GetArgv0Location(unsigned int c) const;