From fb4e99b13d18bb8bcac2c8ab62ff39924ab0be6c Mon Sep 17 00:00:00 2001
From: Bruce Hamilton <bruce.hamilton@jetbrains.com>
Date: Thu, 23 Jan 2025 18:52:50 +0100
Subject: [PATCH] KTOR-7934 Remove Content-Length for browser

---
 .../common/src/io/ktor/client/utils/HeadersUtils.kt  | 12 +++++++++---
 .../io/ktor/client/engine/js/WasmJsClientEngine.kt   |  8 +++++++-
 .../src/io/ktor/client/test/base/ClientLoader.kt     |  6 ++++++
 .../client/tests/ContentEncodingIntegrationTest.kt   |  3 ++-
 4 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/ktor-client/ktor-client-core/common/src/io/ktor/client/utils/HeadersUtils.kt b/ktor-client/ktor-client-core/common/src/io/ktor/client/utils/HeadersUtils.kt
index 1b78fb2e00..750669f3ad 100644
--- a/ktor-client/ktor-client-core/common/src/io/ktor/client/utils/HeadersUtils.kt
+++ b/ktor-client/ktor-client-core/common/src/io/ktor/client/utils/HeadersUtils.kt
@@ -15,10 +15,16 @@ private val DecompressionListAttribute: AttributeKey<MutableList<String>> = Attr
  * (like js and Curl) to make sure all the plugins and checks work with the correct content length and encoding.
  */
 @InternalAPI
-public fun HeadersBuilder.dropCompressionHeaders(method: HttpMethod, attributes: Attributes) {
+public fun HeadersBuilder.dropCompressionHeaders(
+    method: HttpMethod,
+    attributes: Attributes,
+    alwaysRemove: Boolean = false,
+) {
     if (method == HttpMethod.Head || method == HttpMethod.Options) return
-    val header = get(HttpHeaders.ContentEncoding) ?: return
-    attributes.computeIfAbsent(DecompressionListAttribute) { mutableListOf<String>() }.add(header)
+    when(val header = get(HttpHeaders.ContentEncoding)) {
+        null -> if (!alwaysRemove) return
+        else -> attributes.computeIfAbsent(DecompressionListAttribute) { mutableListOf<String>() }.add(header)
+    }
     remove(HttpHeaders.ContentEncoding)
     remove(HttpHeaders.ContentLength)
 }
diff --git a/ktor-client/ktor-client-core/wasmJs/src/io/ktor/client/engine/js/WasmJsClientEngine.kt b/ktor-client/ktor-client-core/wasmJs/src/io/ktor/client/engine/js/WasmJsClientEngine.kt
index 1a1e606777..c0c9cfdc91 100644
--- a/ktor-client/ktor-client-core/wasmJs/src/io/ktor/client/engine/js/WasmJsClientEngine.kt
+++ b/ktor-client/ktor-client-core/wasmJs/src/io/ktor/client/engine/js/WasmJsClientEngine.kt
@@ -173,7 +173,13 @@ internal fun org.w3c.fetch.Headers.mapToKtor(method: HttpMethod, attributes: Att
         append(key, value)
     }
 
-    dropCompressionHeaders(method, attributes)
+    // Content-Encoding is hidden for cross-origin calls,
+    // so browser requests should always ignore Content-Length
+    dropCompressionHeaders(
+        method,
+        attributes,
+        alwaysRemove = PlatformUtils.IS_BROWSER
+    )
 }
 
 /**
diff --git a/ktor-client/ktor-client-test-base/common/src/io/ktor/client/test/base/ClientLoader.kt b/ktor-client/ktor-client-test-base/common/src/io/ktor/client/test/base/ClientLoader.kt
index 0cd15f4b92..b8925b6997 100644
--- a/ktor-client/ktor-client-test-base/common/src/io/ktor/client/test/base/ClientLoader.kt
+++ b/ktor-client/ktor-client-test-base/common/src/io/ktor/client/test/base/ClientLoader.kt
@@ -83,6 +83,12 @@ abstract class ClientLoader(private val timeout: Duration = 1.minutes) {
         return EngineSelectionRule { pattern.matches(it) }
     }
 
+    /** Includes the set of [engines] for the test */
+    fun only(vararg engines: String): EngineSelectionRule {
+        val includePatterns = engines.map(EnginePattern::parse)
+        return EngineSelectionRule { engineName -> includePatterns.any { it.matches(engineName) } }
+    }
+
     /** Excludes the specified [engines] from test execution. */
     fun except(vararg engines: String): EngineSelectionRule = except(engines.asList())
 
diff --git a/ktor-client/ktor-client-tests/common/test/io/ktor/client/tests/ContentEncodingIntegrationTest.kt b/ktor-client/ktor-client-tests/common/test/io/ktor/client/tests/ContentEncodingIntegrationTest.kt
index 29e2f9e3c8..e67043a70a 100644
--- a/ktor-client/ktor-client-tests/common/test/io/ktor/client/tests/ContentEncodingIntegrationTest.kt
+++ b/ktor-client/ktor-client-tests/common/test/io/ktor/client/tests/ContentEncodingIntegrationTest.kt
@@ -20,7 +20,7 @@ class ContentEncodingIntegrationTest : ClientLoader() {
 
     // GZipEncoder is implemented only on JVM.
     @Test
-    fun testGzipWithContentLengthWithoutPlugin() = clientTests(only("jvm:*")) {
+    fun testGzipWithContentLengthWithoutPlugin() = clientTests(only("jvm:*", "web:Js")) {
         test { client ->
             val response = client.get("$TEST_URL/gzip-with-content-length")
             val content = if (response.headers[HttpHeaders.ContentEncoding] == "gzip") {
@@ -43,4 +43,5 @@ class ContentEncodingIntegrationTest : ClientLoader() {
             assertEquals("32", response.headers[HttpHeaders.ContentLength])
         }
     }
+
 }