How to add conditional code in Android.bp - build

Question

AOSP now has new build system, and file Android.bp has replaced Android.mk in many places.
Now I want to list source files conditionally depending on platform.
Say something like this:
if(atom)
{
src: [
.......list of files.......
],
exclude_srcs: [
.......list of files.......
]
} else
{
src: [
.......list of files.......
],
exclude_srcs: [
.......list of files.......
]
}
Any suggestions how to achieve this?
Also, how can I achieve logical operations like NOT, OR etc in conditionals?
Thanks in advance.

Answer 1

Quote from documentation:
By design, Android.bp files are very simple. There are no conditionals or control flow statements - any complexity is handled in build logic written in Go.
You can read it here.

Answer 2

GO
You can write a go script with your conditions. Follow
Is there a way to add/remove module in Android.bp?
What is art.go? And why is it considered a way to write conditionals in bp files?
Conditional compilation
If you just want to include a module conditionally you can define many Android.bp modules and include them based on conditions in Android.mk files.
https://android.googlesource.com/platform/build/soong/+/HEAD/docs/best_practices.md#removing-conditionals
soong_config_modules
You will face parsing errors if any of your Android.bp files include libraries not supported by your AOSP.
To fix that you can use soong_config_modules. Note that this is supported only Android 11 R onwards.
Details are given in https://android.googlesource.com/platform/build/soong/+/refs/heads/master/android/soong_config_modules.go
However, I'll give you an example.
Here I am including special libraries when the AOSP is Android 12. Since these libraries might not be present on lower versions, I will not include iot-camera-system.mk in PRODUCT_PACKAGES so it will not be included as a preinstalled app.
What specifically I will achieve with soong_config_modules is removal of parsing errors when these libraries are not present (Android parses all Android.bp files to form a parse tree, it also checks for the existence of their dependencies and build fails when they are not present).
iot-camera-system.mk
# CameraApp Android Application Package
ifeq ($(PLATFORM_VERSION), $(filter $(PLATFORM_VERSION),S 12))
PRODUCT_PACKAGES += CameraApp
SOONG_CONFIG_NAMESPACES += camera
SOONG_CONFIG_camera += camtargets
SOONG_CONFIG_camera_camtargets := newCameraTarget
else
SOONG_CONFIG_NAMESPACES += camera
SOONG_CONFIG_camera += camtargets
SOONG_CONFIG_camera_camtargets := oldCameraTarget
endif
Android.bp
// This introduces the module type camera_cc_defaults
// If target.mk file contained:
//
// SOONG_CONFIG_NAMESPACES += camera
// SOONG_CONFIG_camera += camtargets
// SOONG_CONFIG_camera_camtargets := newCameraTarget
//
// Then our libs would build with static_libs
soong_config_module_type {
name: "camera_cc_defaults",
module_type: "cc_defaults",
config_namespace: "camera",
variables: ["camtargets"],
properties: ["static_libs"],
}
soong_config_string_variable {
name: "camtargets",
values: ["oldCameraTarget", "newCameraTarget"],
}
camera_cc_defaults {
name: "camera_defaults",
soong_config_variables: {
camtargets: {
oldCameraTarget: {
static_libs: [
],
},
newCameraTarget: {
static_libs: [
"androidx.core_core-ktx",
"androidx.fragment_fragment-ktx",
"androidx.navigation_navigation-fragment-ktx",
"androidx.navigation_navigation-ui-ktx",
"androidx.lifecycle_lifecycle-runtime-ktx",
"kotlinx_coroutines",
"kotlinx_coroutines_android",
],
},
},
},
}
android_library {
name: "utils",
defaults: ["camera_defaults"],
manifest: "utils/src/main/AndroidManifest.xml",
platform_apis: true,
srcs: [
"utils/src/main/java/com/example/android/camera/utils/*.kt",
],
resource_dirs: [
"utils/src/main/res/",
],
static_libs: [
"androidx-constraintlayout_constraintlayout",
"androidx.appcompat_appcompat",
"androidx.localbroadcastmanager_localbroadcastmanager",
"com.google.android.material_material",
"androidx.exifinterface_exifinterface",
"androidx.core_core",
"androidx.preference_preference",
"androidx.fragment_fragment",
"androidx.recyclerview_recyclerview",
"androidx.lifecycle_lifecycle-runtime",
"androidx.lifecycle_lifecycle-extensions",
"kotlin-stdlib",
"kotlin-reflect",
"gson-prebuilt-jar",
],
optimize: {
enabled: false,
},
dex_preopt: {
enabled: false,
},
}
android_app {
name: "CameraApp",
defaults: ["camera_defaults"],
manifest: "app/src/main/AndroidManifest.xml",
privileged: true,
platform_apis: true,
certificate: "platform",
srcs: [
"app/src/main/java/com/example/android/camera2/video/*.kt",
"app/src/main/java/com/example/android/camera2/video/fragments/*.kt",
"app/src/main/java/com/example/android/camera2/video/overlay/*.kt",
],
resource_dirs: [
"app/src/main/res/",
],
static_libs: [
"androidx-constraintlayout_constraintlayout",
"androidx.appcompat_appcompat",
"androidx.localbroadcastmanager_localbroadcastmanager",
"com.google.android.material_material",
"androidx.exifinterface_exifinterface",
"androidx.core_core",
"androidx.preference_preference",
"androidx.fragment_fragment",
"androidx.recyclerview_recyclerview",
"androidx.lifecycle_lifecycle-runtime",
"androidx.lifecycle_lifecycle-extensions",
"kotlin-stdlib",
"kotlin-reflect",
"gson-prebuilt-jar",
"utils",
],
optimize: {
enabled: false,
},
dex_preopt: {
enabled: false,
},
}

Answer 3

this a sample on how to add a conditional in a bp file:
cc_library {
...
srcs: ["generic.cpp"],
arch: {
arm: {
srcs: ["arm.cpp"],
},
x86: {
srcs: ["x86.cpp"],
},
},
}