Vendor dependencies

Let's see how I like this workflow.

vendor/cxx/tools/buck/prelude/kotlin/kotlin.bzl

@@ -0,0 +1,87 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+#
+# This source code is licensed under both the MIT license found in the
+# LICENSE-MIT file in the root directory of this source tree and the Apache
+# License, Version 2.0 found in the LICENSE-APACHE file in the root directory
+# of this source tree.
+
+load("@prelude//android:configuration.bzl", "is_building_android_binary_attr")
+load("@prelude//java:dex_toolchain.bzl", "DexToolchainInfo")
+load("@prelude//java:java.bzl", "dex_min_sdk_version", "is_build_only_native_code", "select_dex_toolchain", "select_java_test_toolchain")
+load(
+    "@prelude//java:java_toolchain.bzl",
+    "JavaPlatformInfo",
+    "JavaTestToolchainInfo",
+    "JavaToolchainInfo",
+)
+load(
+    "@prelude//kotlin:kotlin_toolchain.bzl",
+    "KotlinToolchainInfo",
+)
+load(":kotlin_library.bzl", "kotlin_library_impl")
+load(":kotlin_test.bzl", "kotlin_test_impl")
+
+def _select_java_toolchain():
+    # FIXME: prelude// should be standalone (not refer to fbsource//)
+    return "fbsource//xplat/buck2/platform/java:java"
+
+def _select_kotlin_toolchain():
+    # FIXME: prelude// should be standalone (not refer to fbsource//)
+    return "fbsource//xplat/buck2/platform/kotlin:kotlin"
+
+implemented_rules = {
+    "kotlin_library": kotlin_library_impl,
+    "kotlin_test": kotlin_test_impl,
+}
+
+extra_attributes = {
+    "kotlin_library": {
+        "javac": attrs.option(attrs.one_of(attrs.dep(), attrs.source()), default = None),
+        "resources_root": attrs.option(attrs.string(), default = None),
+        "_build_only_native_code": attrs.default_only(attrs.bool(default = is_build_only_native_code())),
+        "_dex_min_sdk_version": attrs.option(attrs.int(), default = dex_min_sdk_version()),
+        "_dex_toolchain": attrs.option(attrs.exec_dep(
+            providers = [
+                DexToolchainInfo,
+            ],
+        ), default = select_dex_toolchain()),
+        "_is_building_android_binary": is_building_android_binary_attr(),
+        "_java_toolchain": attrs.exec_dep(
+            default = _select_java_toolchain(),
+            providers = [
+                JavaPlatformInfo,
+                JavaToolchainInfo,
+            ],
+        ),
+        "_kotlin_toolchain": attrs.exec_dep(
+            default = _select_kotlin_toolchain(),
+            providers = [
+                KotlinToolchainInfo,
+            ],
+        ),
+    },
+    "kotlin_test": {
+        "javac": attrs.option(attrs.one_of(attrs.dep(), attrs.source()), default = None),
+        "resources_root": attrs.option(attrs.string(), default = None),
+        "_is_building_android_binary": attrs.default_only(attrs.bool(default = False)),
+        "_java_test_toolchain": attrs.exec_dep(
+            default = select_java_test_toolchain(),
+            providers = [
+                JavaTestToolchainInfo,
+            ],
+        ),
+        "_java_toolchain": attrs.exec_dep(
+            default = _select_java_toolchain(),
+            providers = [
+                JavaPlatformInfo,
+                JavaToolchainInfo,
+            ],
+        ),
+        "_kotlin_toolchain": attrs.exec_dep(
+            default = _select_kotlin_toolchain(),
+            providers = [
+                KotlinToolchainInfo,
+            ],
+        ),
+    },
+}