From 5e25ee691af91c6db35b9c61d0be9d6b2483eefc Mon Sep 17 00:00:00 2001
From: Eduard Voronkin <edward.voronkin@gmail.com>
Date: Wed, 29 Oct 2025 12:05:15 -0700
Subject: [PATCH] FASTBuild: generate compile_commands

If `CMAKE_EXPORT_COMPILE_COMMANDS` is set use FASTBuild's `-compdb`
option in order to generate `compile_commands.json` file.

Fixes: #27345
---
 Source/cmGlobalFastbuildGenerator.cxx                 | 11 +++++++++--
 Tests/RunCMake/CMakeLists.txt                         |  2 +-
 .../RunCMake/ExportCompileCommands/RunCMakeTest.cmake |  5 ++++-
 3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/Source/cmGlobalFastbuildGenerator.cxx b/Source/cmGlobalFastbuildGenerator.cxx
index 3f54d23b1d..87bff2e619 100644
--- a/Source/cmGlobalFastbuildGenerator.cxx
+++ b/Source/cmGlobalFastbuildGenerator.cxx
@@ -477,11 +477,18 @@ void cmGlobalFastbuildGenerator::Generate()
       this->GetCMakeInstance()->GetIsInTryCompile()) {
     return;
   }
+  std::string const workingDir =
+    this->GetCMakeInstance()->GetHomeOutputDirectory();
   //  Make "rebuild-bff" target up-to-date after the generation.
   //  This is actually a noop, it just asks CMake to touch the generated file
   //  so FASTBuild would consider the target as up-to-date.
-  AskCMakeToMakeRebuildBFFUpToDate(
-    this->GetCMakeInstance()->GetHomeOutputDirectory());
+  AskCMakeToMakeRebuildBFFUpToDate(workingDir);
+
+  if (this->GlobalSettingIsOn("CMAKE_EXPORT_COMPILE_COMMANDS")) {
+    std::string output;
+    ExecuteFastbuildTarget(workingDir, FASTBUILD_ALL_TARGET_NAME, output,
+                           { "-compdb" });
+  }
 }
 
 void cmGlobalFastbuildGenerator::AskCMakeToMakeRebuildBFFUpToDate(
diff --git a/Tests/RunCMake/CMakeLists.txt b/Tests/RunCMake/CMakeLists.txt
index 35ce7e25b5..8652a5c4e2 100644
--- a/Tests/RunCMake/CMakeLists.txt
+++ b/Tests/RunCMake/CMakeLists.txt
@@ -407,7 +407,7 @@ add_RunCMake_test(Configure -DMSVC_IDE=${MSVC_IDE})
 add_RunCMake_test(CpsExportImportBuild)
 add_RunCMake_test(CpsExportImportInstall)
 add_RunCMake_test(DisallowedCommands)
-if("${CMAKE_GENERATOR}" MATCHES "Unix Makefiles|Ninja")
+if("${CMAKE_GENERATOR}" MATCHES "Unix Makefiles|Ninja|FASTBuild")
   add_RunCMake_test(ExportCompileCommands)
 endif()
 add_RunCMake_test(ExcludeFromAll)
diff --git a/Tests/RunCMake/ExportCompileCommands/RunCMakeTest.cmake b/Tests/RunCMake/ExportCompileCommands/RunCMakeTest.cmake
index b69163782c..3a7f7816d6 100644
--- a/Tests/RunCMake/ExportCompileCommands/RunCMakeTest.cmake
+++ b/Tests/RunCMake/ExportCompileCommands/RunCMakeTest.cmake
@@ -9,4 +9,7 @@ endif()
 run_cmake_with_options(BeforeProject -DCMAKE_PROJECT_INCLUDE_BEFORE=BeforeProjectBEFORE.cmake)
 run_cmake(CustomCompileRule)
 run_cmake(Properties)
-run_cmake(PropertiesGenerateCommand)
+
+if(NOT RunCMake_GENERATOR STREQUAL "FASTBuild")
+  run_cmake(PropertiesGenerateCommand)
+endif()