Ninja: Add missing top-level codegen dependencies on per-directory codegen

In commit 197cb419d1 (add_custom_command: Add CODEGEN support,
2024-05-27, v3.31.0-rc1~394^2) we accidentally left out the global
`codegen` target's dependencies on the per-directory `codegen` targets.
Add them for parity with the `all` target.

Fixes: #26517

Source/cmGlobalNinjaGenerator.cxx

@@ -1661,6 +1661,13 @@ void cmGlobalNinjaGenerator::WriteFolderTargets(std::ostream& os)
           }
         }
 
+        for (DirectoryTarget::Dir const& d : dt.Children) {
+          if (!d.ExcludeFromAll) {
+            build.ExplicitDeps.emplace_back(this->BuildAlias(
+              this->ConvertToNinjaPath(cmStrCat(d.Path, "/codegen")), config));
+          }
+        }
+
         // Write target
         this->WriteBuild(this->EnableCrossConfigBuild() &&
                              this->CrossConfigs.count(config)

Tests/RunCMake/Codegen/RunCMakeTest.cmake

@@ -31,3 +31,7 @@ run_cmake("implicit-depends")
 run_cmake("implicit-depends-append-codegen")
 run_cmake("append-implicit-depends")
 run_cmake("no-output")
+
+# Top-level codegen depends on that of subdirectories.
+run_codegen(SubDir)
+run_codegen(SubDirExcludeFromAll)

Tests/RunCMake/Codegen/SubDir-build-check.cmake

@@ -0,0 +1,9 @@
+set(filename "${RunCMake_TEST_BINARY_DIR}/generated.h")
+if(NOT EXISTS "${filename}")
+  string(APPEND RunCMake_TEST_FAILED "expected file NOT created:\n ${filename}\n")
+endif()
+
+set(filename "${RunCMake_TEST_BINARY_DIR}/SubDir/generated.h")
+if(NOT EXISTS "${filename}")
+  string(APPEND RunCMake_TEST_FAILED "expected file NOT created:\n ${filename}\n")
+endif()

Tests/RunCMake/Codegen/SubDir-common.cmake

@@ -0,0 +1,15 @@
+add_custom_command(
+  OUTPUT
+    ${CMAKE_CURRENT_BINARY_DIR}/generated.h
+  COMMAND
+    ${CMAKE_COMMAND} -E
+        copy ${CMAKE_CURRENT_SOURCE_DIR}/generated.h.in
+        ${CMAKE_CURRENT_BINARY_DIR}/generated.h
+  CODEGEN
+)
+
+add_library(errorlib_top
+  # If this library is built error.c will cause the build to fail
+  error.c
+  ${CMAKE_CURRENT_BINARY_DIR}/generated.h
+)

Tests/RunCMake/Codegen/SubDir.cmake

@@ -0,0 +1,2 @@
+add_subdirectory(SubDir)
+include(SubDir-common.cmake)

Tests/RunCMake/Codegen/SubDir/CMakeLists.txt

@@ -0,0 +1,15 @@
+add_custom_command(
+  OUTPUT
+    ${CMAKE_CURRENT_BINARY_DIR}/generated.h
+  COMMAND
+    ${CMAKE_COMMAND} -E
+        copy ${CMAKE_CURRENT_SOURCE_DIR}/../generated.h.in
+        ${CMAKE_CURRENT_BINARY_DIR}/generated.h
+  CODEGEN
+)
+
+add_library(errorlib_subdir
+  # If this library is built error.c will cause the build to fail
+  ../error.c
+  ${CMAKE_CURRENT_BINARY_DIR}/generated.h
+)

Tests/RunCMake/Codegen/SubDirExcludeFromAll-build-check.cmake

@@ -0,0 +1,9 @@
+set(filename "${RunCMake_TEST_BINARY_DIR}/generated.h")
+if(NOT EXISTS "${filename}")
+  string(APPEND RunCMake_TEST_FAILED "expected file NOT created:\n ${filename}\n")
+endif()
+
+set(filename "${RunCMake_TEST_BINARY_DIR}/SubDir/generated.h")
+if(EXISTS "${filename}")
+  string(APPEND RunCMake_TEST_FAILED "unexpected file created:\n ${filename}\n")
+endif()

Tests/RunCMake/Codegen/SubDirExcludeFromAll.cmake

@@ -0,0 +1,2 @@
+add_subdirectory(SubDir EXCLUDE_FROM_ALL)
+include(SubDir-common.cmake)