From e5ba7a1d14ef6f8afa2491b4dc0131169aaa4a76 Mon Sep 17 00:00:00 2001
From: Arthur LAURENT <arthur.laurent4@gmail.com>
Date: Sun, 21 Jul 2024 16:48:40 +0200
Subject: [PATCH] add a policy to disable module culling

---
 tests/projects/c++/modules/culling/src/hello.mpp   | 10 ++++++++++
 tests/projects/c++/modules/culling/test.lua        |  1 +
 tests/projects/c++/modules/culling/xmake.lua       |  7 +++++++
 xmake/core/project/policy.lua                      |  2 ++
 .../modules/modules_support/dependency_scanner.lua | 14 +++++++++-----
 5 files changed, 29 insertions(+), 5 deletions(-)
 create mode 100644 tests/projects/c++/modules/culling/src/hello.mpp
 create mode 100644 tests/projects/c++/modules/culling/test.lua
 create mode 100644 tests/projects/c++/modules/culling/xmake.lua

diff --git a/tests/projects/c++/modules/culling/src/hello.mpp b/tests/projects/c++/modules/culling/src/hello.mpp
new file mode 100644
index 00000000000..124bd72bc37
--- /dev/null
+++ b/tests/projects/c++/modules/culling/src/hello.mpp
@@ -0,0 +1,10 @@
+module;
+#include <cstdio>
+
+export module hello;
+
+export namespace hello {
+    void say(const char* str) {
+        printf("%s\n", str);
+    }
+}
diff --git a/tests/projects/c++/modules/culling/test.lua b/tests/projects/c++/modules/culling/test.lua
new file mode 100644
index 00000000000..7717f804997
--- /dev/null
+++ b/tests/projects/c++/modules/culling/test.lua
@@ -0,0 +1 @@
+inherit(".test_base")
diff --git a/tests/projects/c++/modules/culling/xmake.lua b/tests/projects/c++/modules/culling/xmake.lua
new file mode 100644
index 00000000000..33d3934b9ff
--- /dev/null
+++ b/tests/projects/c++/modules/culling/xmake.lua
@@ -0,0 +1,7 @@
+add_rules("mode.release", "mode.debug")
+set_languages("c++20")
+
+target("culling")
+    set_kind("static")
+    add_files("src/*.mpp")
+    set_policy("build.c++.modules.culling", false)
diff --git a/xmake/core/project/policy.lua b/xmake/core/project/policy.lua
index 4b5ef9dae6f..2eb2c119387 100644
--- a/xmake/core/project/policy.lua
+++ b/xmake/core/project/policy.lua
@@ -72,6 +72,8 @@ function policy.policies()
             ["build.c++.modules"]                 = {description = "Enable C++ modules for C++ building.", type = "boolean"},
             -- Enable std module
             ["build.c++.modules.std"]             = {description = "Enable std modules.", default = true, type = "boolean"},
+            -- Enable unreferenced and non-public named module culling
+            ["build.c++.modules.culling"]         = {description = "Enable unrefereced and non-public named module culling.", default = true, type = "boolean"},
             -- Try to reuse compiled module bmi file if targets flags permit it
             ["build.c++.modules.tryreuse"]        = {description = "Try to reuse compiled module if possible.", default = true, type = "boolean"},
             -- Enable module taking defines acbount for bmi reuse discrimination
diff --git a/xmake/rules/c++/modules/modules_support/dependency_scanner.lua b/xmake/rules/c++/modules/modules_support/dependency_scanner.lua
index d59a4436a60..cef55fbd5ec 100644
--- a/xmake/rules/c++/modules/modules_support/dependency_scanner.lua
+++ b/xmake/rules/c++/modules/modules_support/dependency_scanner.lua
@@ -422,11 +422,15 @@ function sort_modules_by_dependencies(target, objectfiles, modules)
     local objectfiles_sorted_set = hashset.from(objectfiles_sorted)
     for _, objectfile in ipairs(objectfiles) do
         if not objectfiles_sorted_set:has(objectfile) then
-            -- cull unreferenced non-public named module but add non-module files and implementation modules
-            local _, provide, cppfile = compiler_support.get_provided_module(modules[objectfile])
-            local fileconfig = target:fileconfig(cppfile)
-            local public = fileconfig and fileconfig.public
-            if not provide or public then
+            if target:policy("build.c++.modules.culling") then
+                -- cull unreferenced non-public named module but add non-module files and implementation modules
+                local _, provide, cppfile = compiler_support.get_provided_module(modules[objectfile])
+                local fileconfig = target:fileconfig(cppfile)
+                local public = fileconfig and fileconfig.public
+                if not provide or public then
+                    table.insert(result, objectfile)
+                end
+            else
                 table.insert(result, objectfile)
             end
         end