build: add flatbuffers

bazel/envoy_mobile_dependencies.bzl

@@ -61,6 +61,7 @@ def kotlin_dependencies():
     maven_install(
         artifacts = [
             "com.google.code.findbugs:jsr305:3.0.2",
+            "com.google.flatbuffers:flatbuffers-java:2.0.3",
             # Kotlin
             "org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.3.11",
             "androidx.recyclerview:recyclerview:1.1.0",

bazel/envoy_mobile_repositories.bzl

@@ -10,6 +10,14 @@ def envoy_mobile_repositories():
         urls = ["https://github.com/google/bazel-common/archive/413b433b91f26dbe39cdbc20f742ad6555dd1e27.zip"],
     )
 
+    http_archive(
+        name = "swift_flatbuffers",
+        sha256 = "ffd68aebdfb300c9e82582ea38bf4aa9ce65c77344c94d5047f3be754cc756ea",
+        build_file = "@envoy_mobile//bazel:flatbuffers.BUILD",
+        strip_prefix = "flatbuffers-2.0.0",
+        urls = ["https://github.com/google/flatbuffers/archive/refs/tags/v2.0.0.zip"],
+    )
+
     upstream_envoy_overrides()
     swift_repos()
     kotlin_repos()

bazel/flatbuffers.BUILD

@@ -0,0 +1,13 @@
+load("@build_bazel_rules_swift//swift:swift.bzl", "swift_library")
+
+licenses(["notice"])  # Apache 2
+
+package(
+    default_visibility = ["//visibility:public"],
+)
+
+swift_library(
+    name = "FlatBuffers",
+    srcs = glob(["swift/Sources/FlatBuffers/*.swift"]),
+    module_name = "FlatBuffers",
+)

bazel/flatbuffers.bzl

@@ -0,0 +1,32 @@
+load("@com_github_google_flatbuffers//:build_defs.bzl", "flatbuffer_cc_library", "flatbuffer_library_public")
+load("@envoy_mobile//bazel:kotlin_lib.bzl", "envoy_mobile_kt_library")
+
+def envoy_mobile_flatbuffers_library(name, srcs, namespace, types):
+    flatbuffer_cc_library(
+        name = "{}_fb_cc_lib".format(name),
+        srcs = srcs,
+    )
+
+    directory_path = namespace.replace(".", "/")
+    kotlin_files = [directory_path + "/" + t + ".kt" for t in types]
+    flatbuffer_library_public(
+        name = "{}_fb_kt_srcs".format(name),
+        srcs = srcs,
+        # TODO(snowp): For some reason I can't get this to work with just one output file for java. For now we can avoid dealing with this since basically all use cases of this would result in multiple files for Java.
+        outs = kotlin_files,
+        language_flag = "--kotlin",
+    )
+
+    envoy_mobile_kt_library(
+        name = "{}_fb_kt_lib".format(name),
+        srcs = [":{}_fb_kt_srcs".format(name)],
+        deps = ["@maven//:com_google_flatbuffers_flatbuffers_java"],
+    )
+
+    swift_outputs = ["{}_generated.swift".format(f.replace(".fbs", "")) for f in srcs]
+    flatbuffer_library_public(
+        name = "{}_fb_swift_srcs".format(name),
+        srcs = srcs,
+        outs = swift_outputs,
+        language_flag = "--swift",
+    )

library/swift/BUILD

@@ -49,6 +49,7 @@ swift_library(
     module_name = "Envoy",
     private_deps = [
         "//library/objective-c:envoy_engine_objc_lib",
+        "@swift_flatbuffers//:FlatBuffers",
         "@envoy_mobile_extra_swift_sources//:extra_private_dep",
     ],
     visibility = ["//visibility:public"],

test/fbs/BUILD

@@ -0,0 +1,16 @@
+load("@envoy//bazel:envoy_build_system.bzl", "envoy_package")
+load("//bazel:flatbuffers.bzl", "envoy_mobile_flatbuffers_library")
+
+licenses(["notice"])  # Apache 2
+
+envoy_package()
+
+envoy_mobile_flatbuffers_library(
+    name = "test",
+    srcs = ["test.fbs"],
+    namespace = "Test.Nested",
+    types = [
+        "SomeType",
+        "SomeOtherType",
+    ],
+)

test/fbs/test.fbs

@@ -0,0 +1,10 @@
+namespace Test.Nested;
+
+table SomeType {
+}
+
+table SomeOtherType {
+
+}
+
+root_type SomeType;

test/kotlin/io/envoyproxy/envoymobile/BUILD

@@ -16,6 +16,16 @@ envoy_mobile_kt_test(
     ],
 )
 
+envoy_mobile_kt_test(
+    name = "flatbuffers_test",
+    srcs = [
+        "FlatBuffersTest.kt",
+    ],
+    deps = [
+        "//test/fbs:test_fb_kt_lib",
+    ],
+)
+
 envoy_mobile_kt_test(
     name = "grpc_request_headers_builder_test",
     srcs = [

test/kotlin/io/envoyproxy/envoymobile/FlatBuffersTest.kt

@@ -0,0 +1,16 @@
+package io.envoyproxy.envoymobile
+
+import Test.Nested.SomeType
+import com.google.flatbuffers.FlatBufferBuilder
+import org.junit.Test
+
+class FlatBuffersTest {
+
+  @Test
+  fun `flatbuffers construction`() {
+    // This test doesn't really test any functionality, just demonstrates that we are able to utilize flatbuffers pending
+    // real usage within the code base.
+    val s = SomeType()
+    val f = FlatBufferBuilder()
+  }
+}

test/swift/integration/BUILD

@@ -40,6 +40,18 @@ envoy_mobile_swift_test(
     ],
 )
 
+envoy_mobile_swift_test(
+    name = "flatbuffer_test",
+    srcs = [
+        "FlatBufferTest.swift",
+    ] + [
+        "//test/fbs:test_fb_swift_srcs",
+    ],
+    deps = [
+        "@swift_flatbuffers//:FlatBuffers",
+    ],
+)
+
 envoy_cc_library(
     name = "test_extensions_cc",
     srcs = [

test/swift/integration/FlatBufferTest.swift

@@ -0,0 +1,12 @@
+import Envoy
+import FlatBuffers
+import XCTest
+
+final class FlatBufferTest: XCTestCase {
+    func testCreateFlatBuffer() {
+        // This test simply verifies that we can import both the generated types as
+        // well as upstream FlatBuffers.
+        _ = Test_Nested_SomeTypeT()
+        _ = FlatBufferBuilder()
+    }
+}