fix!: make encoding/decoding RLP lists non-ambiguous by returning empty List instead of null

ethers-abi/src/main/kotlin/io/ethers/abi/call/ContractCall.kt

@@ -94,7 +94,7 @@ abstract class ReadWriteContractCall<C, S : PendingInclusion<*>, B : ReadWriteCo
         }
 
         if (gasPrice != null) {
-            if (accessList != null) {
+            if (accessList.isNotEmpty()) {
                 return TxAccessList(
                     to = to,
                     value = value ?: BigInteger.ZERO,
@@ -103,7 +103,7 @@ abstract class ReadWriteContractCall<C, S : PendingInclusion<*>, B : ReadWriteCo
                     gasPrice = gasPrice!!,
                     data = data,
                     chainId = chainId,
-                    accessList = accessList!!,
+                    accessList = accessList,
                 )
             }
 
@@ -221,7 +221,7 @@ abstract class ReadContractCall<C, B : ReadContractCall<C, B>>(
             call.nonce = value
         }
 
-    var accessList: List<AccessList.Item>?
+    var accessList: List<AccessList.Item>
         get() = call.accessList
         @JvmSynthetic set(value) {
             call.accessList = value
@@ -257,7 +257,7 @@ abstract class ReadContractCall<C, B : ReadContractCall<C, B>>(
         return self
     }
 
-    fun accessList(value: List<AccessList.Item>?): B {
+    fun accessList(value: List<AccessList.Item>): B {
         call.accessList = value
         return self
     }

ethers-core/src/main/kotlin/io/ethers/core/types/AccessList.kt

@@ -39,7 +39,7 @@ object AccessList {
             override fun rlpDecode(rlp: RlpDecoder): Item? {
                 return rlp.decodeList {
                     val address = rlp.decode(Address) ?: return null
-                    val storageKeys = rlp.decodeAsList(Hash) ?: return null
+                    val storageKeys = rlp.decodeAsList(Hash)
 
                     Item(address, storageKeys)
                 }

ethers-core/src/main/kotlin/io/ethers/core/types/CallRequest.kt

@@ -28,7 +28,7 @@ class CallRequest {
         @JvmSynthetic set
     var data: Bytes? = null
         @JvmSynthetic set
-    var accessList: List<AccessList.Item>? = null
+    var accessList: List<AccessList.Item> = emptyList()
         @JvmSynthetic set
     var chainId: Long = -1L
         @JvmSynthetic set
@@ -129,9 +129,9 @@ private class CallRequestSerializer : JsonSerializer<CallRequest>() {
         if (value.data != null) {
             gen.writeStringField("input", value.data.toString())
         }
-        if (value.accessList != null) {
+        if (value.accessList.isNotEmpty()) {
             gen.writeArrayFieldStart("accessList")
-            for (item in value.accessList!!) {
+            for (item in value.accessList) {
                 // delegate to AccessList.Item serializer
                 gen.writeObject(item)
             }

ethers-core/src/main/kotlin/io/ethers/core/types/RPCTransaction.kt

@@ -36,7 +36,7 @@ data class RPCTransaction(
     override val gasFeeCap: BigInteger,
     override val gasTipCap: BigInteger,
     override val data: Bytes?,
-    override val accessList: List<AccessList.Item>?,
+    override val accessList: List<AccessList.Item>,
     override val chainId: Long,
     override val type: TxType,
     val v: Long,
@@ -68,7 +68,7 @@ private class RPCTransactionDeserializer : JsonDeserializer<RPCTransaction>() {
         var gasTipCap: BigInteger? = null
         var data: Bytes? = null
         var type = -1L
-        var accessList: List<AccessList.Item>? = null
+        var accessList: List<AccessList.Item> = emptyList()
         var chainId: Long = ChainId.NONE
         var v = -1L
         lateinit var r: BigInteger
@@ -95,7 +95,7 @@ private class RPCTransactionDeserializer : JsonDeserializer<RPCTransaction>() {
                 "input" -> data = p.readBytesEmptyAsNull()
                 "type" -> type = p.readHexLong()
                 "accessList" -> accessList = p.readListOf(AccessList.Item::class.java)
-                "chainId" -> chainId = p.readHexLong()
+                "chainId" -> p.ifNotNull { chainId = p.readHexLong() }
                 "v" -> v = p.readHexLong()
                 "r" -> r = p.readHexBigInteger()
                 "s" -> s = p.readHexBigInteger()

ethers-core/src/main/kotlin/io/ethers/core/types/transaction/Transaction.kt

@@ -28,7 +28,7 @@ interface Transaction {
     val gasFeeCap: BigInteger
     val data: Bytes?
     val chainId: Long
-    val accessList: List<AccessList.Item>?
+    val accessList: List<AccessList.Item>
     val type: TxType
     val blobFeeCap: BigInteger?
     val blobVersionedHashes: List<Hash>?

ethers-core/src/main/kotlin/io/ethers/core/types/transaction/TxAccessList.kt

@@ -22,7 +22,7 @@ class TxAccessList(
     override val gasPrice: BigInteger,
     override val data: Bytes?,
     override val chainId: Long,
-    override var accessList: List<AccessList.Item>?,
+    override var accessList: List<AccessList.Item>,
 ) : TransactionUnsigned {
     init {
         if (!ChainId.isValid(chainId)) {
@@ -67,7 +67,7 @@ class TxAccessList(
         gasPrice: BigInteger = this.gasPrice,
         data: Bytes? = this.data,
         chainId: Long = this.chainId,
-        accessList: List<AccessList.Item>? = this.accessList,
+        accessList: List<AccessList.Item> = this.accessList,
     ): TxAccessList {
         return TxAccessList(
             to = to,
@@ -107,7 +107,7 @@ class TxAccessList(
         result = 31 * result + gasPrice.hashCode()
         result = 31 * result + (data?.hashCode() ?: 0)
         result = 31 * result + chainId.hashCode()
-        result = 31 * result + (accessList?.hashCode() ?: 0)
+        result = 31 * result + accessList.hashCode()
         return result
     }
 

ethers-core/src/main/kotlin/io/ethers/core/types/transaction/TxBlob.kt

@@ -28,7 +28,7 @@ class TxBlob(
     override val gasTipCap: BigInteger,
     override val data: Bytes?,
     override val chainId: Long,
-    override var accessList: List<AccessList.Item>?,
+    override var accessList: List<AccessList.Item>,
     override val blobFeeCap: BigInteger,
     override val blobVersionedHashes: List<Hash>,
     val sidecar: Sidecar? = null,
@@ -42,7 +42,7 @@ class TxBlob(
         gasTipCap: BigInteger,
         data: Bytes?,
         chainId: Long,
-        accessList: List<AccessList.Item>?,
+        accessList: List<AccessList.Item>,
         blobFeeCap: BigInteger,
         sidecar: Sidecar,
     ) : this(
@@ -101,7 +101,7 @@ class TxBlob(
         gasTipCap: BigInteger = this.gasTipCap,
         data: Bytes? = this.data,
         chainId: Long = this.chainId,
-        accessList: List<AccessList.Item>? = this.accessList,
+        accessList: List<AccessList.Item> = this.accessList,
         blobFeeCap: BigInteger = this.blobFeeCap,
         blobHashes: List<Hash> = this.blobVersionedHashes,
         sidecar: Sidecar? = this.sidecar,
@@ -153,7 +153,7 @@ class TxBlob(
         result = 31 * result + gasTipCap.hashCode()
         result = 31 * result + (data?.hashCode() ?: 0)
         result = 31 * result + chainId.hashCode()
-        result = 31 * result + (accessList?.hashCode() ?: 0)
+        result = 31 * result + (accessList.hashCode())
         result = 31 * result + blobFeeCap.hashCode()
         result = 31 * result + blobVersionedHashes.hashCode()
         result = 31 * result + (sidecar?.hashCode() ?: 0)
@@ -202,11 +202,11 @@ class TxBlob(
             const val COMMITMENT_LENGTH = 48
             const val PROOF_LENGTH = 48
 
-            override fun rlpDecode(rlp: RlpDecoder): Sidecar? {
+            override fun rlpDecode(rlp: RlpDecoder): Sidecar {
                 return Sidecar(
-                    blobs = rlp.decodeAsList(Bytes) ?: return null,
-                    commitments = rlp.decodeAsList(Bytes) ?: return null,
-                    proofs = rlp.decodeAsList(Bytes) ?: return null,
+                    blobs = rlp.decodeAsList(Bytes),
+                    commitments = rlp.decodeAsList(Bytes),
+                    proofs = rlp.decodeAsList(Bytes),
                 )
             }
         }
@@ -228,7 +228,7 @@ class TxBlob(
                 data = rlp.decode(Bytes),
                 accessList = rlp.decodeAsList(AccessList.Item),
                 blobFeeCap = rlp.decodeBigIntegerElse(BigInteger.ZERO),
-                blobVersionedHashes = rlp.decodeAsList(Hash) ?: emptyList(),
+                blobVersionedHashes = rlp.decodeAsList(Hash),
             )
         }
     }

ethers-core/src/main/kotlin/io/ethers/core/types/transaction/TxDynamicFee.kt

@@ -23,7 +23,7 @@ class TxDynamicFee(
     override val gasTipCap: BigInteger,
     override val data: Bytes?,
     override val chainId: Long,
-    override var accessList: List<AccessList.Item>?,
+    override var accessList: List<AccessList.Item>,
 ) : TransactionUnsigned {
     init {
         if (!ChainId.isValid(chainId)) {
@@ -70,7 +70,7 @@ class TxDynamicFee(
         gasTipCap: BigInteger = this.gasTipCap,
         data: Bytes? = this.data,
         chainId: Long = this.chainId,
-        accessList: List<AccessList.Item>? = this.accessList,
+        accessList: List<AccessList.Item> = this.accessList,
     ): TxDynamicFee {
         return TxDynamicFee(
             to = to,
@@ -113,7 +113,7 @@ class TxDynamicFee(
         result = 31 * result + gasTipCap.hashCode()
         result = 31 * result + (data?.hashCode() ?: 0)
         result = 31 * result + chainId.hashCode()
-        result = 31 * result + (accessList?.hashCode() ?: 0)
+        result = 31 * result + accessList.hashCode()
         return result
     }
 

ethers-core/src/main/kotlin/io/ethers/core/types/transaction/TxLegacy.kt

@@ -24,8 +24,8 @@ data class TxLegacy(
     override val gasFeeCap: BigInteger
         get() = gasPrice
 
-    override val accessList: List<AccessList.Item>?
-        get() = null
+    override val accessList: List<AccessList.Item>
+        get() = emptyList()
 
     override val type: TxType
         get() = TxType.Legacy

ethers-core/src/test/kotlin/fixtures/TxAccessListFactory.kt

@@ -15,7 +15,7 @@ object TxAccessListFactory {
         gas: Long = 0,
         gasPrice: BigInteger = BigInteger.ZERO,
         data: Bytes? = null,
-        accessList: List<AccessList.Item>? = null,
+        accessList: List<AccessList.Item> = emptyList(),
     ): TxAccessList {
         return TxAccessList(to, value, nonce, gas, gasPrice, data, chainId, accessList)
     }

ethers-core/src/test/kotlin/fixtures/TxDynamicFeeFactory.kt

@@ -16,7 +16,7 @@ object TxDynamicFeeFactory {
         gasFeeCap: BigInteger = BigInteger.ZERO,
         gasTipCap: BigInteger = BigInteger.ZERO,
         data: Bytes? = null,
-        accessList: List<AccessList.Item>? = null,
+        accessList: List<AccessList.Item> = emptyList(),
     ): TxDynamicFee {
         return TxDynamicFee(to, value, nonce, gas, gasFeeCap, gasTipCap, data, chainId, accessList)
     }

ethers-core/src/test/kotlin/io/ethers/core/types/TxpoolTest.kt

@@ -83,7 +83,7 @@ class TxpoolTest : FunSpec({
                         yParity = -1,
                         blobVersionedHashes = null,
                         blobFeeCap = null,
-                        accessList = null,
+                        accessList = emptyList(),
                         gasFeeCap = BigInteger("4010000000"),
                         gasTipCap = BigInteger("4010000000"),
                     ),
@@ -111,7 +111,7 @@ class TxpoolTest : FunSpec({
                         yParity = -1,
                         blobVersionedHashes = null,
                         blobFeeCap = null,
-                        accessList = null,
+                        accessList = emptyList(),
                         gasFeeCap = BigInteger("7431800000"),
                         gasTipCap = BigInteger("7431800000"),
                     ),
@@ -199,7 +199,7 @@ class TxpoolTest : FunSpec({
                     value = BigInteger("23000000000000000"),
                     type = TxType.Legacy,
                     chainId = 1L,
-                    accessList = null,
+                    accessList = emptyList(),
                     gasFeeCap = BigInteger("53739672778"),
                     gasTipCap = BigInteger("53739672778"),
                     v = 37,
@@ -225,7 +225,7 @@ class TxpoolTest : FunSpec({
                     value = BigInteger.ZERO,
                     type = TxType.Legacy,
                     chainId = 1L,
-                    accessList = null,
+                    accessList = emptyList(),
                     gasFeeCap = BigInteger("5500000000"),
                     gasTipCap = BigInteger("5500000000"),
                     v = 37,

ethers-core/src/test/kotlin/io/ethers/core/types/transactions/TransactionSignedTest.kt

@@ -1,5 +1,6 @@
 package io.ethers.core.types.transactions
 
+import io.ethers.core.Jackson
 import io.ethers.core.types.AccessList
 import io.ethers.core.types.Address
 import io.ethers.core.types.Bytes
@@ -11,8 +12,12 @@ import io.ethers.core.types.transaction.TxBlob
 import io.ethers.core.types.transaction.TxDynamicFee
 import io.ethers.core.types.transaction.TxLegacy
 import io.kotest.core.spec.style.FunSpec
+import io.kotest.datatest.WithDataTestName
+import io.kotest.datatest.withData
 import io.kotest.matchers.shouldBe
+import io.kotest.matchers.shouldNotBe
 import io.kotest.matchers.string.shouldBeEqualIgnoringCase
+import java.io.File
 
 class TransactionSignedTest : FunSpec({
     test("rlp encode/decode TxLegacy without chain ID") {
@@ -147,7 +152,7 @@ class TransactionSignedTest : FunSpec({
             gasTipCap = "21000000000".toBigInteger(),
             data = Bytes("0x1214abcdef12445980"),
             chainId = 1L,
-            accessList = null,
+            accessList = emptyList(),
             blobFeeCap = "21000000000".toBigInteger(),
             blobVersionedHashes = listOf(Hash("0x010657f37554c781402a22917dee2f75def7ab966d7b770905398eba3c444014")),
         )
@@ -178,7 +183,7 @@ class TransactionSignedTest : FunSpec({
             gasTipCap = "21000000000".toBigInteger(),
             data = Bytes("0x1214abcdef12445980"),
             chainId = 1L,
-            accessList = null,
+            accessList = emptyList(),
             blobFeeCap = "21000000000".toBigInteger(),
             sidecar = TxBlob.Sidecar(
                 blobs = listOf(Bytes(ByteArray(TxBlob.Sidecar.BLOB_LENGTH))),
@@ -202,4 +207,46 @@ class TransactionSignedTest : FunSpec({
         val decoded = TransactionSigned.rlpDecode(rlp)
         decoded shouldBe signed
     }
-})
+
+    context("RLP roundtrip encode/decode test") {
+        val reader = Jackson.MAPPER.readerFor(RoundtripCase::class.java)
+        val rlpBatches = TransactionSignedTest::class.java.getResource("/testdata/txsigned")!!
+            .file
+            .let(::File)
+            .walkTopDown()
+            .filter { it.isFile && it.name.endsWith(".json") }
+            .map { it.name to reader.readValues<RoundtripCase>(it).readAll() }
+
+        rlpBatches.forEach { (dumpName, cases) ->
+            context(dumpName) {
+                withData(cases) {
+                    val decoded = TransactionSigned.rlpDecode(it.rlp.value)
+
+                    // it's enough to check that "hash" and "from" have expected values:
+                    // - if any value was different from original tx, the "hash" will be different
+                    // - if signature is different from original tx, the "from" will fail or will be different
+                    decoded shouldNotBe null
+                    decoded!!.hash shouldBe it.hash
+                    decoded.from shouldBe it.from
+
+                    val rlpEncoded = Bytes(decoded.toRlp())
+                    rlpEncoded shouldBe it.rlp
+                }
+            }
+        }
+    }
+}) {
+    data class RoundtripCase(val hash: Hash, val from: Address, val rlp: Bytes) : WithDataTestName {
+        override fun dataTestName() = hash.toString()
+    }
+}
+
+// Used to dump additional roundtrip test cases, need to run from providers module
+/*fun main() {
+    val provider = Provider(HttpClient("RPC_URL"))
+    val block = provider.getBlockWithTransactions(19111477).sendAwait().unwrap()
+    val encoded = block.transactions.map { TransactionSignedTest.RoundtripCase(it.hash, it.from, Bytes(it.toSignedTransaction().toRlp())) }
+
+    // copy the result to resource folder
+    Jackson.MAPPER.writeValue(File("./transactions-${block.number}.json"), encoded)
+}*/