Non-release profiles of lcli panic by default due to argument processing failure

[jmcph4]

Description

When invoked in non-release profiles, lcli panics by default during argument parsing. This is most likely due to an error in Clap: clap-rs/clap#1546.

Credit to @jimmygchen for the discovery.

Version

$ rustc --version
rustc 1.70.0 (90c541806 2023-05-31)
$ git rev-parse HEAD
dfcb3363c757671eb19d5f8e519b4b94ac74677a
$ cargo run --bin lighthouse -- --version
Lighthouse v4.3.0-dfcb336
BLS library: blst
SHA256 hardware acceleration: true
Allocator: system
Profile: debug
Specs: mainnet (true), minimal (false), gnosis (false)

Present Behaviour

$ cargo run --profile dev --bin lcli
thread 'main' panicked at 'Global arguments cannot be required.

	'spec' is marked as global and required', /home/jmcph4/.cargo/registry/src/index.crates.io-6f17d22bba15001f/clap-2.34.0/src/app/parser.rs:208:9
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
$ echo $?
101

Expected Behaviour

Lighthouse should not panic on this condition, but instead display the default help text and return a 1 exit code. Compare the above behaviour to the release profile behaviour:

$ cargo run --profile release --bin lcli
Failed to run lcli: Unknown subcommand . See --help.
$ echo $?
1

Steps to resolve

As per this comment on the Clap ticket, removing all instances of both required and default_value should work:

diff --git a/lcli/src/main.rs b/lcli/src/main.rs
index d072beaa4..4206a2f47 100644
--- a/lcli/src/main.rs
+++ b/lcli/src/main.rs
@@ -38,7 +38,6 @@ fn main() {
                 .long("spec")
                 .value_name("STRING")
                 .takes_value(true)
-                .required(true)
                 .possible_values(&["minimal", "mainnet", "gnosis"])
                 .default_value("mainnet")
                 .global(true),
@@ -361,7 +360,6 @@ fn main() {
                         .index(2)
                         .value_name("BIP39_MNENMONIC")
                         .takes_value(true)
-                        .required(true)
                         .default_value(
                             "replace nephew blur decorate waste convince soup column \
                             orient excite play baby",
@@ -382,7 +380,6 @@ fn main() {
                         .help("The block hash used when generating an execution payload. This \
                             value is used for `execution_payload_header.block_hash` as well as \
                             `execution_payload_header.random`")
-                        .required(true)
                         .default_value(
                             "0x0000000000000000000000000000000000000000000000000000000000000000",
                         ),
@@ -400,7 +397,6 @@ fn main() {
                         .value_name("INTEGER")
                         .takes_value(true)
                         .help("The base fee per gas field in the execution payload generated.")
-                        .required(true)
                         .default_value("1000000000"),
                 )
                 .arg(
@@ -409,7 +405,6 @@ fn main() {
                         .value_name("INTEGER")
                         .takes_value(true)
                         .help("The gas limit field in the execution payload generated.")
-                        .required(true)
                         .default_value("30000000"),