refactor: pad when needed and not sooner

l1-contracts/src/core/libraries/decoders/TxsDecoder.sol

@@ -14,7 +14,7 @@ import {Hash} from "../Hash.sol";
  * @dev Assumes the input trees to be padded.
  *
  * -------------------
- * You can use scripts/l2_block_data_specification_comment.py to generate the below outline.
+ * You can use scripts/l2_block_data_specification_comment.py to generate the below outline. --> SCRIPT STALE NOW!
  * -------------------
  * L2 Body Data Specification
  * -------------------
@@ -68,25 +68,25 @@ library TxsDecoder {
   }
 
   /**
-   * @notice Computes consumables for the block
-   * @param _body - The L2 block calldata.
-   * @return diffRoot - The root of the diff tree (new note hashes, nullifiers etc)
+   * @notice Computes txs effects hash
+   * @param _body - The L2 block body calldata.
+   * @return The txs effects hash.
    */
   function decode(bytes calldata _body) internal pure returns (bytes32) {
     ArrayOffsets memory offsets;
     Counts memory counts;
     ConsumablesVars memory vars;
     uint256 offset = 0;
 
-    {
-      uint256 count = read4(_body, offset); // number of tx effects
-      offset += 0x4;
-      vars.baseLeaves = new bytes32[](count);
-    }
+    uint32 numTxEffects = uint32(read4(_body, offset));
+    uint256 numTxEffectsToPad = computeNumTxEffectsToPad(numTxEffects);
+
+    offset += 0x4;
+    vars.baseLeaves = new bytes32[](numTxEffects + numTxEffectsToPad);
 
     // Data starts after header. Look at L2 Block Data specification at the top of this file.
     {
-      for (uint256 i = 0; i < vars.baseLeaves.length; i++) {
+      for (uint256 i = 0; i < numTxEffects; i++) {
         /*
          * Compute the leaf to insert.
          * Leaf_i = (
@@ -179,6 +179,12 @@ library TxsDecoder {
 
         vars.baseLeaves[i] = Hash.sha256ToField(vars.baseLeaf);
       }
+
+      // We pad base leaves with hashes of empty tx effect.
+      for (uint256 i = numTxEffects; i < vars.baseLeaves.length; i++) {
+        // Value taken from tx_effect.test.ts "hash of empty tx effect matches snapshot" test case
+        vars.baseLeaves[i] = hex"0071f7630d28ce02cc1ca8b15c44953f84a39e1478445395247ae04dfa213c0e";
+      }
     }
 
     return computeRoot(vars.baseLeaves);
@@ -344,4 +350,26 @@ library TxsDecoder {
   function read4(bytes calldata _data, uint256 _offset) internal pure returns (uint256) {
     return uint256(uint32(bytes4(slice(_data, _offset, 4))));
   }
+
+  function computeNumTxEffectsToPad(uint32 _numTxEffects) internal pure returns (uint32) {
+    // 2 is the minimum number of tx effects so we have to handle the following 2 cases separately
+    if (_numTxEffects == 0) {
+      return 2;
+    } else if (_numTxEffects == 1) {
+      return 1;
+    }
+
+    uint32 v = _numTxEffects;
+
+    // the following rounds _numTxEffects up to the next power of 2 (works only for 4 bytes value!)
+    v--;
+    v |= v >> 1;
+    v |= v >> 2;
+    v |= v >> 4;
+    v |= v >> 8;
+    v |= v >> 16;
+    v++;
+
+    return v - _numTxEffects;
+  }
 }

l1-contracts/test/Rollup.t.sol

@@ -5,6 +5,7 @@ pragma solidity >=0.8.18;
 import {DecoderBase} from "./decoders/Base.sol";
 
 import {DataStructures} from "../src/core/libraries/DataStructures.sol";
+import {Constants} from "../src/core/libraries/ConstantsGen.sol";
 
 import {Registry} from "../src/core/messagebridge/Registry.sol";
 import {Inbox} from "../src/core/messagebridge/Inbox.sol";
@@ -15,6 +16,8 @@ import {AvailabilityOracle} from "../src/core/availability_oracle/AvailabilityOr
 import {NaiveMerkle} from "./merkle/Naive.sol";
 import {MerkleTestUtil} from "./merkle/TestUtil.sol";
 
+import {TxsDecoderHelper} from "./decoders/helpers/TxsDecoderHelper.sol";
+
 /**
  * Blocks are generated using the `integration_l1_publisher.test.ts` tests.
  * Main use of these test is shorter cycles when updating the decoder contract.
@@ -25,6 +28,7 @@ contract RollupTest is DecoderBase {
   Outbox internal outbox;
   Rollup internal rollup;
   MerkleTestUtil internal merkleTestUtil;
+  TxsDecoderHelper internal txsHelper;
 
   AvailabilityOracle internal availabilityOracle;
 
@@ -38,6 +42,7 @@ contract RollupTest is DecoderBase {
     registry.upgrade(address(rollup), address(inbox), address(outbox));
 
     merkleTestUtil = new MerkleTestUtil();
+    txsHelper = new TxsDecoderHelper();
   }
 
   function testMixedBlock() public {
@@ -128,6 +133,7 @@ contract RollupTest is DecoderBase {
     bytes memory header = full.block.header;
     bytes32 archive = full.block.archive;
     bytes memory body = full.block.body;
+    uint32 numTxs = full.block.numTxs;
 
     // We jump to the time of the block.
     vm.warp(full.block.decodedHeader.globalVariables.timestamp);
@@ -145,19 +151,25 @@ contract RollupTest is DecoderBase {
 
     bytes32 l2ToL1MessageTreeRoot;
     {
-      uint256 treeHeight =
-        merkleTestUtil.calculateTreeHeightFromSize(full.messages.l2ToL1Messages.length);
+      uint256 numTxsWithPadding = txsHelper.computeNumTxEffectsToPad(numTxs) + numTxs;
+      uint256 numMessagesWithPadding = numTxsWithPadding * Constants.MAX_NEW_L2_TO_L1_MSGS_PER_TX;
+
+      uint256 treeHeight = merkleTestUtil.calculateTreeHeightFromSize(numMessagesWithPadding);
       NaiveMerkle tree = new NaiveMerkle(treeHeight);
-      for (uint256 i = 0; i < full.messages.l2ToL1Messages.length; i++) {
-        tree.insertLeaf(full.messages.l2ToL1Messages[i]);
+      for (uint256 i = 0; i < numMessagesWithPadding; i++) {
+        if (i < full.messages.l2ToL1Messages.length) {
+          tree.insertLeaf(full.messages.l2ToL1Messages[i]);
+        } else {
+          tree.insertLeaf(bytes32(0));
+        }
       }
 
       l2ToL1MessageTreeRoot = tree.computeRoot();
     }
 
     (bytes32 root,) = outbox.roots(full.block.decodedHeader.globalVariables.blockNumber);
 
-    assertEq(l2ToL1MessageTreeRoot, root);
+    assertEq(l2ToL1MessageTreeRoot, root, "Invalid l2 to l1 message tree root");
 
     assertEq(rollup.archive(), archive, "Invalid archive");
   }

l1-contracts/test/decoders/Base.sol

@@ -37,6 +37,9 @@ contract DecoderBase is Test {
     bytes body;
     DecodedHeader decodedHeader;
     bytes header;
+    // Note: The following could be decoded from body but having it explicitaly here makes tests more robust against
+    // decoder changes
+    uint32 numTxs;
     bytes32 publicInputsHash;
     bytes32 txsEffectsHash;
   }

l1-contracts/test/decoders/Decoders.t.sol

@@ -277,4 +277,39 @@ contract DecodersTest is DecoderBase {
     assertEq(bytesAdvanced, encodedLogs.length, "Advanced by an incorrect number of bytes");
     assertEq(logsHash, referenceLogsHashFromIteration3, "Incorrect logs hash");
   }
+
+  function testTxsDecoderCorrectlyComputesNumTxEffectsToPad() public {
+    // Minimum num txs is 2 so when there are no real txs we need to pad to 2
+    uint32 numTxEffects = 0;
+    uint32 paddedNumTxEffects = txsHelper.computeNumTxEffectsToPad(numTxEffects);
+    assertEq(paddedNumTxEffects, 2, "Incorrect number of tx effects to pad");
+
+    numTxEffects = 1;
+    paddedNumTxEffects = txsHelper.computeNumTxEffectsToPad(numTxEffects);
+    assertEq(paddedNumTxEffects, 2 ** 1 - numTxEffects, "Incorrect number of tx effects to pad");
+
+    numTxEffects = 3;
+    paddedNumTxEffects = txsHelper.computeNumTxEffectsToPad(numTxEffects);
+    assertEq(paddedNumTxEffects, 2 ** 2 - numTxEffects, "Incorrect number of tx effects to pad");
+
+    numTxEffects = 5;
+    paddedNumTxEffects = txsHelper.computeNumTxEffectsToPad(numTxEffects);
+    assertEq(paddedNumTxEffects, 2 ** 3 - numTxEffects, "Incorrect number of tx effects to pad");
+
+    numTxEffects = 8;
+    paddedNumTxEffects = txsHelper.computeNumTxEffectsToPad(numTxEffects);
+    assertEq(paddedNumTxEffects, 2 ** 3 - numTxEffects, "Incorrect number of tx effects to pad");
+
+    numTxEffects = 10;
+    paddedNumTxEffects = txsHelper.computeNumTxEffectsToPad(numTxEffects);
+    assertEq(paddedNumTxEffects, 2 ** 4 - numTxEffects, "Incorrect number of tx effects to pad");
+
+    numTxEffects = 16;
+    paddedNumTxEffects = txsHelper.computeNumTxEffectsToPad(numTxEffects);
+    assertEq(paddedNumTxEffects, 2 ** 4 - numTxEffects, "Incorrect number of tx effects to pad");
+
+    numTxEffects = 17;
+    paddedNumTxEffects = txsHelper.computeNumTxEffectsToPad(numTxEffects);
+    assertEq(paddedNumTxEffects, 2 ** 5 - numTxEffects, "Incorrect number of tx effects to pad");
+  }
 }

l1-contracts/test/decoders/helpers/TxsDecoderHelper.sol

@@ -17,4 +17,8 @@ contract TxsDecoderHelper {
   {
     return TxsDecoder.computeKernelLogsHash(0, _kernelLogs);
   }
+
+  function computeNumTxEffectsToPad(uint32 _numTxEffects) external pure returns (uint32) {
+    return TxsDecoder.computeNumTxEffectsToPad(_numTxEffects);
+  }
 }

l1-contracts/test/fixtures/empty_block_0.json

@@ -5,35 +5,26 @@
     "sender": "0x9965507D1a55bcC2695C58ba16FB37d819B0A4dc"
   },
   "messages": {
-    "l2ToL1Messages": [
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000"
-    ]
+    "l2ToL1Messages": []
   },
   "block": {
-    "archive": "0x29598370fa40a50b7fbb99e501f11527a69e104a43c8eefbfe66888f137e7e49",
-    "body": "0x0000000400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
-    "txsEffectsHash": "0x008194e3dd375d5d878dcf9546bb5c2c77e165c6b1bef9aead8ceb35c3762bd5",
+    "archive": "0x122e56310a16134c202e94b3ba9cb74de123f7ec493e601d2f0b6da00cf57a4a",
+    "body": "0x00000000",
+    "txsEffectsHash": "0x00df6b1c97b9e01113fa0363d9ff71c85addc74e92b22d433b2fb082d2493896",
     "decodedHeader": {
       "contentCommitment": {
         "inHash": "0x00089a9d421a82c4a25f7acbebe69e638d5b064fa8a60e018793dcb0be53752c",
-        "outHash": "0x00efcbdb79553ae6863646bf36441755bc344a9a4af335fadc6659594faa4316",
-        "txTreeHeight": 2,
-        "txsEffectsHash": "0x008194e3dd375d5d878dcf9546bb5c2c77e165c6b1bef9aead8ceb35c3762bd5"
+        "outHash": "0x0007638bb56b6dda2b64b8f76841114ac3a87a1820030e2e16772c4d294879c3",
+        "txTreeHeight": 1,
+        "txsEffectsHash": "0x00df6b1c97b9e01113fa0363d9ff71c85addc74e92b22d433b2fb082d2493896"
       },
       "globalVariables": {
         "blockNumber": 1,
         "chainId": 31337,
         "timestamp": 0,
         "version": 1,
-        "coinbase": "0x5e65711eaf5606f1f42dd36579261833e54595ee",
-        "feeRecipient": "0x00eafbad09eab548a89726e2a735bdcadc37aa4c318ed7a12d9be6a7542e517e"
+        "coinbase": "0x66440eb666440eb666440eb666440eb666440eb6",
+        "feeRecipient": "0x061ca689507c7f1ccc68c2ad086c9d5d94f50869cb1b718c6a46aaf77a4500ba"
       },
       "lastArchive": {
         "nextAvailableLeafIndex": 1,
@@ -46,21 +37,22 @@
         },
         "partialStateReference": {
           "noteHashTree": {
-            "nextAvailableLeafIndex": 256,
+            "nextAvailableLeafIndex": 128,
             "root": "0x16642d9ccd8346c403aa4c3fa451178b22534a27035cdaa6ec34ae53b29c50cb"
           },
           "nullifierTree": {
-            "nextAvailableLeafIndex": 384,
+            "nextAvailableLeafIndex": 256,
             "root": "0x0bcfa3e9f1a8922ee92c6dc964d6595907c1804a86753774322b468f69d4f278"
           },
           "publicDataTree": {
-            "nextAvailableLeafIndex": 192,
+            "nextAvailableLeafIndex": 128,
             "root": "0x0572c8db882674dd026b8877fbba1b700a4407da3ae9ce5fa43215a28163362b"
           }
         }
       }
     },
-    "header": "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",
-    "publicInputsHash": "0x009e67eb54715bba61c94f475f6d4bf81b775da316c2c9a6a12506851f760bf0"
+    "header": "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",
+    "publicInputsHash": "0x00b833c76dd93572e83879eeb4085a3cd71f24831384fb4d3fe531ed87b859e3",
+    "numTxs": 0
   }
 }

l1-contracts/test/fixtures/empty_block_1.json

@@ -5,39 +5,30 @@
     "sender": "0x9965507D1a55bcC2695C58ba16FB37d819B0A4dc"
   },
   "messages": {
-    "l2ToL1Messages": [
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000",
-      "0x0000000000000000000000000000000000000000000000000000000000000000"
-    ]
+    "l2ToL1Messages": []
   },
   "block": {
-    "archive": "0x045487d0ec498eb3f7f027715db8d67cc060604058bc5dd3e2e39fb47fe0ea17",
-    "body": "0x0000000400000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
-    "txsEffectsHash": "0x008194e3dd375d5d878dcf9546bb5c2c77e165c6b1bef9aead8ceb35c3762bd5",
+    "archive": "0x0d53ab5014f578345d853cd208bda74db64358fef8e5f646240db05893f6e780",
+    "body": "0x00000000",
+    "txsEffectsHash": "0x00df6b1c97b9e01113fa0363d9ff71c85addc74e92b22d433b2fb082d2493896",
     "decodedHeader": {
       "contentCommitment": {
         "inHash": "0x00089a9d421a82c4a25f7acbebe69e638d5b064fa8a60e018793dcb0be53752c",
-        "outHash": "0x00efcbdb79553ae6863646bf36441755bc344a9a4af335fadc6659594faa4316",
-        "txTreeHeight": 2,
-        "txsEffectsHash": "0x008194e3dd375d5d878dcf9546bb5c2c77e165c6b1bef9aead8ceb35c3762bd5"
+        "outHash": "0x0007638bb56b6dda2b64b8f76841114ac3a87a1820030e2e16772c4d294879c3",
+        "txTreeHeight": 1,
+        "txsEffectsHash": "0x00df6b1c97b9e01113fa0363d9ff71c85addc74e92b22d433b2fb082d2493896"
       },
       "globalVariables": {
         "blockNumber": 2,
         "chainId": 31337,
-        "timestamp": 1711036059,
+        "timestamp": 1711637579,
         "version": 1,
-        "coinbase": "0x5e65711eaf5606f1f42dd36579261833e54595ee",
-        "feeRecipient": "0x00eafbad09eab548a89726e2a735bdcadc37aa4c318ed7a12d9be6a7542e517e"
+        "coinbase": "0x66440eb666440eb666440eb666440eb666440eb6",
+        "feeRecipient": "0x061ca689507c7f1ccc68c2ad086c9d5d94f50869cb1b718c6a46aaf77a4500ba"
       },
       "lastArchive": {
         "nextAvailableLeafIndex": 2,
-        "root": "0x29598370fa40a50b7fbb99e501f11527a69e104a43c8eefbfe66888f137e7e49"
+        "root": "0x122e56310a16134c202e94b3ba9cb74de123f7ec493e601d2f0b6da00cf57a4a"
       },
       "stateReference": {
         "l1ToL2MessageTree": {
@@ -46,21 +37,22 @@
         },
         "partialStateReference": {
           "noteHashTree": {
-            "nextAvailableLeafIndex": 512,
+            "nextAvailableLeafIndex": 256,
             "root": "0x16642d9ccd8346c403aa4c3fa451178b22534a27035cdaa6ec34ae53b29c50cb"
           },
           "nullifierTree": {
-            "nextAvailableLeafIndex": 640,
+            "nextAvailableLeafIndex": 384,
             "root": "0x0bcfa3e9f1a8922ee92c6dc964d6595907c1804a86753774322b468f69d4f278"
           },
           "publicDataTree": {
-            "nextAvailableLeafIndex": 320,
+            "nextAvailableLeafIndex": 192,
             "root": "0x0572c8db882674dd026b8877fbba1b700a4407da3ae9ce5fa43215a28163362b"
           }
         }
       }
     },
-    "header": "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",
-    "publicInputsHash": "0x00e9cfdd839060c90c216e1cecd24c5570a84e380e2bc640fd9dbbb5b2dd0718"
+    "header": "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",
+    "publicInputsHash": "0x00035031752fa374209f1ec4bc08613cae25ba65779c10130681421f6e71c6d9",
+    "numTxs": 0
   }
 }