Ensure difficulty/hash/epoch overrides change the ChainSpec (#2798)

* Unify loading of eth2_network_config

* Apply overrides at lighthouse binary level

* Remove duplicate override values

* Add merge values to existing net configs

* Make override flags global

* Add merge fields to testing config

* Add one to TTD

* Fix failing engine tests

* Fix test compile error

* Remove TTD flags

* Move get_eth2_network_config

* Fix warn

* Address review comments

boot_node/Cargo.toml

@@ -23,3 +23,4 @@ hex = "0.4.2"
 serde = "1.0.116"
 serde_derive = "1.0.116"
 serde_json = "1.0.66"
+eth2_network_config = { path = "../common/eth2_network_config" }

boot_node/src/config.rs

@@ -1,5 +1,6 @@
-use beacon_node::{get_data_dir, get_eth2_network_config, set_network_config};
+use beacon_node::{get_data_dir, set_network_config};
 use clap::ArgMatches;
+use eth2_network_config::Eth2NetworkConfig;
 use lighthouse_network::discv5::{enr::CombinedKey, Discv5Config, Enr};
 use lighthouse_network::{
     discovery::{create_enr_builder_from_config, load_enr_from_disk, use_or_load_enr},
@@ -7,7 +8,6 @@ use lighthouse_network::{
 };
 use serde_derive::{Deserialize, Serialize};
 use ssz::Encode;
-use std::convert::TryFrom;
 use std::net::SocketAddr;
 use std::{marker::PhantomData, path::PathBuf};
 use types::EthSpec;
@@ -23,15 +23,13 @@ pub struct BootNodeConfig<T: EthSpec> {
     phantom: PhantomData<T>,
 }
 
-impl<T: EthSpec> TryFrom<&ArgMatches<'_>> for BootNodeConfig<T> {
-    type Error = String;
-
-    fn try_from(matches: &ArgMatches<'_>) -> Result<Self, Self::Error> {
+impl<T: EthSpec> BootNodeConfig<T> {
+    pub fn new(
+        matches: &ArgMatches<'_>,
+        eth2_network_config: &Eth2NetworkConfig,
+    ) -> Result<Self, String> {
         let data_dir = get_data_dir(matches);
 
-        // Try and grab network config from input CLI params
-        let eth2_network_config = get_eth2_network_config(matches)?;
-
         // Try and obtain bootnodes
 
         let boot_nodes = {

boot_node/src/lib.rs

@@ -2,7 +2,7 @@
 use clap::ArgMatches;
 use slog::{o, Drain, Level, Logger};
 
-use std::convert::TryFrom;
+use eth2_network_config::Eth2NetworkConfig;
 use std::fs::File;
 use std::path::PathBuf;
 mod cli;
@@ -19,6 +19,7 @@ pub fn run(
     lh_matches: &ArgMatches<'_>,
     bn_matches: &ArgMatches<'_>,
     eth_spec_id: EthSpecId,
+    eth2_network_config: &Eth2NetworkConfig,
     debug_level: String,
 ) {
     let debug_level = match debug_level.as_str() {
@@ -56,8 +57,12 @@ pub fn run(
     let log = slog_scope::logger();
     // Run the main function emitting any errors
     if let Err(e) = match eth_spec_id {
-        EthSpecId::Minimal => main::<types::MinimalEthSpec>(lh_matches, bn_matches, log),
-        EthSpecId::Mainnet => main::<types::MainnetEthSpec>(lh_matches, bn_matches, log),
+        EthSpecId::Minimal => {
+            main::<types::MinimalEthSpec>(lh_matches, bn_matches, eth2_network_config, log)
+        }
+        EthSpecId::Mainnet => {
+            main::<types::MainnetEthSpec>(lh_matches, bn_matches, eth2_network_config, log)
+        }
     } {
         slog::crit!(slog_scope::logger(), "{}", e);
     }
@@ -66,6 +71,7 @@ pub fn run(
 fn main<T: EthSpec>(
     lh_matches: &ArgMatches<'_>,
     bn_matches: &ArgMatches<'_>,
+    eth2_network_config: &Eth2NetworkConfig,
     log: slog::Logger,
 ) -> Result<(), String> {
     // Builds a custom executor for the bootnode
@@ -74,8 +80,8 @@ fn main<T: EthSpec>(
         .build()
         .map_err(|e| format!("Failed to build runtime: {}", e))?;
 
-    // Parse the CLI args into a useable config
-    let config: BootNodeConfig<T> = BootNodeConfig::try_from(bn_matches)?;
+    // parse the CLI args into a useable config
+    let config: BootNodeConfig<T> = BootNodeConfig::new(bn_matches, eth2_network_config)?;
 
     // Dump config if `dump-config` flag is set
     let dump_config = clap_utils::parse_optional::<PathBuf>(lh_matches, "dump-config")?;