KTOR-8082 Add formFieldLimit system property (#4617)

Author: e5l

ktor-server/ktor-server-core/api/ktor-server-core.api

@@ -1000,11 +1000,11 @@ public final class io/ktor/server/plugins/UnsupportedMediaTypeException : io/kto
 }
 
 public final class io/ktor/server/request/ApplicationReceiveFunctionsJvmKt {
+	public static final fun getDEFAULT_FORM_FIELD_LIMIT ()J
 	public static final fun receiveStream (Lio/ktor/server/application/ApplicationCall;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 }
 
 public final class io/ktor/server/request/ApplicationReceiveFunctionsKt {
-	public static final field DEFAULT_FORM_FIELD_MAX_SIZE J
 	public static final fun getFormFieldLimit (Lio/ktor/server/application/ApplicationCall;)J
 	public static final fun receive (Lio/ktor/server/application/ApplicationCall;Lio/ktor/util/reflect/TypeInfo;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public static final fun receive (Lio/ktor/server/application/ApplicationCall;Lkotlin/reflect/KClass;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;

ktor-server/ktor-server-core/api/ktor-server-core.klib.api

@@ -1602,9 +1602,6 @@ final object io.ktor.server.routing/TrailingSlashRouteSelector : io.ktor.server.
     final suspend fun evaluate(io.ktor.server.routing/RoutingResolveContext, kotlin/Int): io.ktor.server.routing/RouteSelectorEvaluation // io.ktor.server.routing/TrailingSlashRouteSelector.evaluate|evaluate(io.ktor.server.routing.RoutingResolveContext;kotlin.Int){}[0]
 }
 
-final const val io.ktor.server.request/DEFAULT_FORM_FIELD_MAX_SIZE // io.ktor.server.request/DEFAULT_FORM_FIELD_MAX_SIZE|{}DEFAULT_FORM_FIELD_MAX_SIZE[0]
-    final fun <get-DEFAULT_FORM_FIELD_MAX_SIZE>(): kotlin/Long // io.ktor.server.request/DEFAULT_FORM_FIELD_MAX_SIZE.<get-DEFAULT_FORM_FIELD_MAX_SIZE>|<get-DEFAULT_FORM_FIELD_MAX_SIZE>(){}[0]
-
 final val io.ktor.server.application/ApplicationStarted // io.ktor.server.application/ApplicationStarted|{}ApplicationStarted[0]
     final fun <get-ApplicationStarted>(): io.ktor.events/EventDefinition<io.ktor.server.application/Application> // io.ktor.server.application/ApplicationStarted.<get-ApplicationStarted>|<get-ApplicationStarted>(){}[0]
 final val io.ktor.server.application/ApplicationStarting // io.ktor.server.application/ApplicationStarting|{}ApplicationStarting[0]
@@ -1649,6 +1646,8 @@ final val io.ktor.server.plugins/mutableOriginConnectionPoint // io.ktor.server.
     final fun (io.ktor.server.application/ApplicationCall).<get-mutableOriginConnectionPoint>(): io.ktor.server.plugins/MutableOriginConnectionPoint // io.ktor.server.plugins/mutableOriginConnectionPoint.<get-mutableOriginConnectionPoint>|<get-mutableOriginConnectionPoint>@io.ktor.server.application.ApplicationCall(){}[0]
 final val io.ktor.server.plugins/origin // io.ktor.server.plugins/origin|@io.ktor.server.request.ApplicationRequest{}origin[0]
     final fun (io.ktor.server.request/ApplicationRequest).<get-origin>(): io.ktor.http/RequestConnectionPoint // io.ktor.server.plugins/origin.<get-origin>|<get-origin>@io.ktor.server.request.ApplicationRequest(){}[0]
+final val io.ktor.server.request/DEFAULT_FORM_FIELD_LIMIT // io.ktor.server.request/DEFAULT_FORM_FIELD_LIMIT|{}DEFAULT_FORM_FIELD_LIMIT[0]
+    final fun <get-DEFAULT_FORM_FIELD_LIMIT>(): kotlin/Long // io.ktor.server.request/DEFAULT_FORM_FIELD_LIMIT.<get-DEFAULT_FORM_FIELD_LIMIT>|<get-DEFAULT_FORM_FIELD_LIMIT>(){}[0]
 final val io.ktor.server.request/httpMethod // io.ktor.server.request/httpMethod|@io.ktor.server.request.ApplicationRequest{}httpMethod[0]
     final fun (io.ktor.server.request/ApplicationRequest).<get-httpMethod>(): io.ktor.http/HttpMethod // io.ktor.server.request/httpMethod.<get-httpMethod>|<get-httpMethod>@io.ktor.server.request.ApplicationRequest(){}[0]
 final val io.ktor.server.request/httpVersion // io.ktor.server.request/httpVersion|@io.ktor.server.request.ApplicationRequest{}httpVersion[0]

ktor-server/ktor-server-core/common/src/io/ktor/server/request/ApplicationReceiveFunctions.kt

@@ -20,7 +20,7 @@ import kotlin.reflect.*
 private val FORM_FIELD_LIMIT = AttributeKey<Long>("FormFieldLimit")
 
 @PublishedApi
-internal const val DEFAULT_FORM_FIELD_MAX_SIZE: Long = 50 * 1024 * 1024
+internal expect val DEFAULT_FORM_FIELD_LIMIT: Long
 
 /**
  * A pipeline for processing incoming content.
@@ -176,7 +176,7 @@ public suspend inline fun ApplicationCall.receiveChannel(): ByteReadChannel = re
  */
 public var ApplicationCall.formFieldLimit: Long
     get() {
-        return attributes.getOrNull(FORM_FIELD_LIMIT) ?: DEFAULT_FORM_FIELD_MAX_SIZE
+        return attributes.getOrNull(FORM_FIELD_LIMIT) ?: DEFAULT_FORM_FIELD_LIMIT
     }
     set(value) {
         attributes.put(FORM_FIELD_LIMIT, value)

ktor-server/ktor-server-core/jsAndWasmShared/src/io/ktor/server/request/ApplicationReceiveFunctions.jsAndWasmShared.kt

@@ -0,0 +1,9 @@
+/*
+ * Copyright 2014-2025 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package io.ktor.server.request
+
+@PublishedApi
+internal actual val DEFAULT_FORM_FIELD_LIMIT: Long
+    get() = 50 * 1024 * 1024L

ktor-server/ktor-server-core/jvm/src/io/ktor/server/engine/DefaultTransformJvm.kt

@@ -45,7 +45,7 @@ internal actual fun PipelineContext<*, PipelineCall>.multiPartData(rc: ByteReadC
             rc,
             contentType,
             contentLength,
-            call.formFieldLimit
+            formFieldLimit = call.formFieldLimit
         )
     } catch (_: UnsupportedMediaTypeExceptionCIO) {
         throw UnsupportedMediaTypeException(ContentType.parse(contentType))

ktor-server/ktor-server-core/jvm/src/io/ktor/server/request/ApplicationReceiveFunctionsJvm.kt

@@ -14,3 +14,7 @@ import java.io.*
  */
 @Suppress("NOTHING_TO_INLINE")
 public suspend inline fun ApplicationCall.receiveStream(): InputStream = receive()
+
+@PublishedApi
+internal actual val DEFAULT_FORM_FIELD_LIMIT: Long
+    get() = System.getProperty("io.ktor.server.request.formFieldLimit")?.toLongOrNull() ?: (50 * 1024 * 1024L)

ktor-server/ktor-server-core/posix/src/io/ktor/server/request/ApplicationReceiveFunctions.posix.kt

@@ -0,0 +1,9 @@
+/*
+ * Copyright 2014-2025 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package io.ktor.server.request
+
+@PublishedApi
+internal actual val DEFAULT_FORM_FIELD_LIMIT: Long
+    get() = 50 * 1024 * 1024L