Ninja: Account for explicit target dependencies via CODEGEN

When a "normal" target (e.g., an executable) depends on a custom target
that is not part of `all`, and that custom target owns the output of a
custom command marked `CODEGEN`, an explicit `add_dependencies` from
the normal to custom target must be incorporated in `codegen`.

Amends commit 197cb419d1 (add_custom_command: Add CODEGEN support,
2024-05-27, v3.31.0-rc1~394^2), which already incorporated such logic
in the Unix Makefile generator, but was not tested nor implemented for
Ninja.

Fixes: #28092

Source/cmGlobalNinjaGenerator.cxx

@@ -1558,6 +1558,21 @@ void cmGlobalNinjaGenerator::AppendTargetDependsClosure(
   outputs.insert(outs.begin(), outs.end());
 }
 
+void cmGlobalNinjaGenerator::AppendCodegenTargetDepends(
+  cmGeneratorTarget const* target, cmNinjaDeps& deps,
+  std::string const& config) const
+{
+  std::set<std::string> const& codegenDeps = target->Target->GetCodegenDeps();
+  for (cmTargetDepend const& targetDep :
+       this->GetTargetDirectDepends(target)) {
+    if (targetDep->IsInBuildSystem() &&
+        codegenDeps.count(targetDep->GetName())) {
+      this->AppendTargetOutputs(targetDep, deps, config,
+                                DependOnTargetArtifact);
+    }
+  }
+}
+
 void cmGlobalNinjaGenerator::AddTargetAlias(std::string const& alias,
                                             cmGeneratorTarget* target,
                                             std::string const& config)
@@ -1727,6 +1742,9 @@ void cmGlobalNinjaGenerator::WriteFolderTargets(std::ostream& os)
           if (this->IsExcludedFromAllInConfig(t, config)) {
             continue;
           }
+
+          this->AppendCodegenTargetDepends(t.GT, build.ExplicitDeps, config);
+
           std::vector<cmSourceFile const*> customCommandSources;
           t.GT->GetCustomCommands(customCommandSources, config);
           for (cmSourceFile const* sf : customCommandSources) {

Source/cmGlobalNinjaGenerator.h

@@ -524,6 +524,10 @@ private:
   void CloseRulesFileStream();
   void CleanMetaData();
 
+  void AppendCodegenTargetDepends(cmGeneratorTarget const* target,
+                                  cmNinjaDeps& deps,
+                                  std::string const& config) const;
+
   /// Write the common disclaimer text at the top of each build file.
   void WriteDisclaimer(std::ostream& os) const;
 

Tests/RunCMake/Codegen/RunCMakeTest.cmake

@@ -25,6 +25,7 @@ run_codegen("min-graph-3")
 run_codegen("add-dependencies")
 run_codegen("add-custom-command-depends")
 run_codegen("byproducts")
+run_codegen("add-dependencies-not-all")
 
 # Error handling
 run_cmake("implicit-depends")

Tests/RunCMake/Codegen/add-dependencies-not-all-build-check.cmake

@@ -0,0 +1,5 @@
+set(filename "${RunCMake_TEST_BINARY_DIR}/generated.h")
+if (NOT EXISTS "${filename}")
+  set(RunCMake_TEST_FAILED "expected file NOT created:\n ${filename}")
+  return()
+endif()

Tests/RunCMake/Codegen/add-dependencies-not-all.cmake

@@ -0,0 +1,17 @@
+add_executable(main
+    main.c
+)
+
+add_custom_command(
+  OUTPUT generated.h
+  COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_SOURCE_DIR}/generated.h.in
+                                   ${CMAKE_CURRENT_BINARY_DIR}/generated.h
+  CODEGEN
+)
+
+# N.B. h_creator is *not* added to ALL.
+add_custom_target(h_creator DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/generated.h)
+
+# This test will fail if add_dependencies isn't accounted for in the
+# codegen build graph
+add_dependencies(main h_creator)

Tests/RunCMake/Codegen/add-dependencies.cmake

@@ -13,6 +13,6 @@ add_custom_command(
 
 add_custom_target(hpp_creator ALL DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/generated.hpp)
 
-# This test will fail if add_dependencies isn't account for in the
+# This test will fail if add_dependencies isn't accounted for in the
 # codegen build graph
 add_dependencies(hpp_creator foobar)