From 799aedd6319b13032afdca03d845263e27f098d0 Mon Sep 17 00:00:00 2001
From: Pawan Dhananjay <pawandhananjay@gmail.com>
Date: Thu, 20 Jan 2022 23:05:42 +0000
Subject: [PATCH] Add default config options for transition constants (#2940)

## Issue Addressed

Continuation to #2934

## Proposed Changes

Currently, we have the transition fields in the config (`TERMINAL_TOTAL_DIFFICULTY`, `TERMINAL_BLOCK_HASH` and `TERMINAL_BLOCK_HASH_ACTIVATION_EPOCH`) as mandatory fields.

This is causing compatibility issues with other client BN's (nimbus and teku v22.1.0) which don't return these fields on a `eth/v1/config/spec` api call. Since we don't use this values until the merge, I think it's okay to have default values set for these fields as well to ensure compatibility.
---
 consensus/types/src/chain_spec.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/consensus/types/src/chain_spec.rs b/consensus/types/src/chain_spec.rs
index 0bd0acb96..f191eb867 100644
--- a/consensus/types/src/chain_spec.rs
+++ b/consensus/types/src/chain_spec.rs
@@ -611,9 +611,15 @@ pub struct Config {
     #[serde(default)]
     pub preset_base: String,
 
+    // TODO(merge): remove this default
+    #[serde(default = "default_terminal_total_difficulty")]
     #[serde(with = "eth2_serde_utils::quoted_u256")]
     pub terminal_total_difficulty: Uint256,
+    // TODO(merge): remove this default
+    #[serde(default = "default_terminal_block_hash")]
     pub terminal_block_hash: Hash256,
+    // TODO(merge): remove this default
+    #[serde(default = "default_terminal_block_hash_activation_epoch")]
     pub terminal_block_hash_activation_epoch: Epoch,
 
     #[serde(with = "eth2_serde_utils::quoted_u64")]
@@ -682,6 +688,20 @@ fn default_bellatrix_fork_epoch() -> Option<MaybeQuoted<Epoch>> {
     None
 }
 
+fn default_terminal_total_difficulty() -> Uint256 {
+    "115792089237316195423570985008687907853269984665640564039457584007913129638912"
+        .parse()
+        .unwrap()
+}
+
+fn default_terminal_block_hash() -> Hash256 {
+    Hash256::zero()
+}
+
+fn default_terminal_block_hash_activation_epoch() -> Epoch {
+    Epoch::new(u64::MAX)
+}
+
 impl Default for Config {
     fn default() -> Self {
         let chain_spec = MainnetEthSpec::default_spec();