Support empty buffers on Gzip decompression (#139)

Fixes #138 

Gzipped responses that return an empty message Buffer fail with an
`EOFException`, halting the request chain.

gradle/libs.versions.toml

@@ -32,6 +32,7 @@ dokka-plugin = { module = "org.jetbrains.dokka:dokka-gradle-plugin", version.ref
 junit = { module = "junit:junit", version.ref = "junit" }
 kotlin-coroutines-android = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-android", version.ref = "coroutines" }
 kotlin-coroutines-core = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-core", version.ref = "coroutines" }
+kotlin-coroutines-test = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-test", version.ref = "coroutines" }
 kotlin-jsr223 = { module = "org.jetbrains.kotlin:kotlin-scripting-jsr223", version.ref = "kotlin" }
 kotlin-plugin = { module = "org.jetbrains.kotlin:kotlin-gradle-plugin", version.ref = "kotlin" }
 kotlin-reflect = { module = "org.jetbrains.kotlin:kotlin-reflect", version.ref = "kotlin" }
@@ -44,6 +45,7 @@ moshiKotlin = { module = "com.squareup.moshi:moshi-kotlin", version.ref = "moshi
 moshiKotlinCodegen = { module = "com.squareup.moshi:moshi-kotlin-codegen", version.ref = "moshi" }
 okhttp-core = { module = "com.squareup.okhttp3:okhttp", version.ref = "okhttp" }
 okhttp-tls = { module = "com.squareup.okhttp3:okhttp-tls", version.ref = "okhttp" }
+okhttp-mockwebserver = { module = "com.squareup.okhttp3:mockwebserver", version.ref = "okhttp" }
 okio-core = { module = "com.squareup.okio:okio", version.ref = "okio" }
 protobuf-java = { module = "com.google.protobuf:protobuf-java", version.ref = "protobuf" }
 protobuf-java-util = { module = "com.google.protobuf:protobuf-java-util", version.ref = "protobuf" }

library/src/main/kotlin/com/connectrpc/compression/GzipCompressionPool.kt

@@ -38,6 +38,8 @@ object GzipCompressionPool : CompressionPool {
 
     override fun decompress(buffer: Buffer): Buffer {
         val result = Buffer()
+        if (buffer.size == 0L) return result
+
         GzipSource(buffer).use {
             while (it.read(result, Int.MAX_VALUE.toLong()) != -1L) {
                 // continue reading.

library/src/test/kotlin/com/connectrpc/compression/GzipCompressionPoolTest.kt

@@ -43,4 +43,11 @@ class GzipCompressionPoolTest {
         val resultString = compressionPool.decompress(result).readUtf8()
         assertThat(resultString).isEqualTo("some_string")
     }
+
+    @Test
+    fun emptyBufferGzipDecompression() {
+        val compressionPool = GzipCompressionPool
+        val resultString = compressionPool.decompress(Buffer()).readUtf8()
+        assertThat(resultString).isEqualTo("")
+    }
 }

library/src/test/kotlin/com/connectrpc/protocols/ConnectInterceptorTest.kt

@@ -170,6 +170,34 @@ class ConnectInterceptorTest {
         assertThat(decompressed.readUtf8()).isEqualTo("message")
     }
 
+    @Test
+    fun compressedEmptyRequestMessage() {
+        val config = ProtocolClientConfig(
+            host = "https://connectrpc.com",
+            serializationStrategy = serializationStrategy,
+            requestCompression = RequestCompression(1, GzipCompressionPool),
+            compressionPools = listOf(GzipCompressionPool),
+        )
+        val connectInterceptor = ConnectInterceptor(config)
+        val unaryFunction = connectInterceptor.unaryFunction()
+
+        val request = unaryFunction.requestFunction(
+            HTTPRequest(
+                url = URL(config.host),
+                contentType = "content_type",
+                headers = emptyMap(),
+                message = "".commonAsUtf8ToByteArray(),
+                methodSpec = MethodSpec(
+                    path = "",
+                    requestClass = Any::class,
+                    responseClass = Any::class,
+                ),
+            ),
+        )
+        val decompressed = GzipCompressionPool.decompress(Buffer().write(request.message!!))
+        assertThat(decompressed.readUtf8()).isEqualTo("")
+    }
+
     @Test
     fun uncompressedResponseMessage() {
         val config = ProtocolClientConfig(
@@ -214,6 +242,28 @@ class ConnectInterceptorTest {
         assertThat(response.message.readUtf8()).isEqualTo("message")
     }
 
+    @Test
+    fun compressedEmptyResponseMessage() {
+        val config = ProtocolClientConfig(
+            host = "https://connectrpc.com",
+            serializationStrategy = serializationStrategy,
+            compressionPools = listOf(GzipCompressionPool),
+        )
+        val connectInterceptor = ConnectInterceptor(config)
+        val unaryFunction = connectInterceptor.unaryFunction()
+
+        val response = unaryFunction.responseFunction(
+            HTTPResponse(
+                code = Code.OK,
+                headers = mapOf(CONTENT_ENCODING to listOf(GzipCompressionPool.name())),
+                message = Buffer(),
+                trailers = emptyMap(),
+                tracingInfo = null,
+            ),
+        )
+        assertThat(response.message.readUtf8()).isEqualTo("")
+    }
+
     @Test
     fun responseError() {
         val config = ProtocolClientConfig(

okhttp/build.gradle.kts

@@ -16,6 +16,12 @@ dependencies {
     implementation(libs.kotlin.coroutines.core)
 
     api(project(":library"))
+
+    testImplementation(libs.assertj)
+    testImplementation(libs.okhttp.mockwebserver)
+    testImplementation(libs.kotlin.coroutines.test)
+    testImplementation(project(":extensions:google-java"))
+    testImplementation(project(":examples:generated-google-java"))
 }
 
 mavenPublishing {

okhttp/src/test/kotlin/com/connectrpc/okhttp/MockWebServerRule.kt

@@ -0,0 +1,38 @@
+// Copyright 2022-2023 The Connect Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.connectrpc.okhttp
+
+import okhttp3.mockwebserver.MockWebServer
+import org.junit.rules.TestWatcher
+import org.junit.runner.Description
+
+class MockWebServerRule(
+    private val port: Int = 0,
+) : TestWatcher() {
+
+    lateinit var server: MockWebServer
+        private set
+
+    override fun starting(description: Description) {
+        super.starting(description)
+        server = MockWebServer()
+        server.start(port)
+    }
+
+    override fun finished(description: Description) {
+        super.finished(description)
+        server.shutdown()
+    }
+}

okhttp/src/test/kotlin/com/connectrpc/okhttp/MockWebServerTests.kt

@@ -0,0 +1,74 @@
+// Copyright 2022-2023 The Connect Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package com.connectrpc.okhttp
+
+import com.connectrpc.Code
+import com.connectrpc.ProtocolClientConfig
+import com.connectrpc.RequestCompression
+import com.connectrpc.compression.GzipCompressionPool
+import com.connectrpc.eliza.v1.ElizaServiceClient
+import com.connectrpc.eliza.v1.sayRequest
+import com.connectrpc.extensions.GoogleJavaProtobufStrategy
+import com.connectrpc.impl.ProtocolClient
+import com.connectrpc.protocols.NetworkProtocol
+import kotlinx.coroutines.test.runTest
+import okhttp3.OkHttpClient
+import okhttp3.Protocol
+import okhttp3.mockwebserver.MockResponse
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.Rule
+import org.junit.Test
+
+class MockWebServerTests {
+
+    @get:Rule val mockWebServerRule = MockWebServerRule()
+
+    @Test
+    fun `compressed empty failure response is parsed correctly`() = runTest {
+        mockWebServerRule.server.enqueue(
+            MockResponse().apply {
+                addHeader("accept-encoding", "gzip")
+                addHeader("content-encoding", "gzip")
+                setBody("{}")
+                setResponseCode(401)
+            },
+        )
+
+        val host = mockWebServerRule.server.url("/")
+
+        val protocolClient = ProtocolClient(
+            ConnectOkHttpClient(
+                OkHttpClient.Builder()
+                    .protocols(listOf(Protocol.HTTP_2, Protocol.HTTP_1_1))
+                    .build(),
+            ),
+            ProtocolClientConfig(
+                host = host.toString(),
+                serializationStrategy = GoogleJavaProtobufStrategy(),
+                networkProtocol = NetworkProtocol.CONNECT,
+                requestCompression = RequestCompression(0, GzipCompressionPool),
+                compressionPools = listOf(GzipCompressionPool),
+            ),
+        )
+
+        val response = ElizaServiceClient(protocolClient).say(sayRequest { sentence = "hello" })
+
+        mockWebServerRule.server.takeRequest().apply {
+            assertThat(path).isEqualTo("/connectrpc.eliza.v1.ElizaService/Say")
+        }
+
+        assertThat(response.code).isEqualTo(Code.UNKNOWN)
+    }
+}