Allow compilation with no slasher backend (#3888)

## Proposed Changes

Allowing compiling without MDBX by running:

```bash
CARGO_INSTALL_EXTRA_FLAGS="--no-default-features" make
```

The reasons to do this are several:

- Save compilation time if the slasher won't be used
- Work around compilation errors in slasher backend dependencies (our pinned version of MDBX is currently not compiling on FreeBSD with certain compiler versions).

## Additional Info

When I opened this PR we were using resolver v1 which [doesn't disable default features in dependencies](https://doc.rust-lang.org/cargo/reference/features.html#resolver-version-2-command-line-flags), and `mdbx` is default for the `slasher` crate. Even after the resolver got changed to v2 in #3697 compiling with `--no-default-features` _still_ wasn't turning off the slasher crate's default features, so I added `default-features = false` in all the places we depend on it.

Co-authored-by: Michael Sproul <micsproul@gmail.com>

Makefile

@@ -38,15 +38,24 @@ PROFILE ?= release
 # they run for different forks.
 FORKS=phase0 altair merge capella
 
+# Extra flags for Cargo
+CARGO_INSTALL_EXTRA_FLAGS?=
+
 # Builds the Lighthouse binary in release (optimized).
 #
 # Binaries will most likely be found in `./target/release`
 install:
-	cargo install --path lighthouse --force --locked --features "$(FEATURES)" --profile "$(PROFILE)"
+	cargo install --path lighthouse --force --locked \
+		--features "$(FEATURES)" \
+		--profile "$(PROFILE)" \
+		$(CARGO_INSTALL_EXTRA_FLAGS)
 
 # Builds the lcli binary in release (optimized).
 install-lcli:
-	cargo install --path lcli --force --locked --features "$(FEATURES)" --profile "$(PROFILE)"
+	cargo install --path lcli --force --locked \
+		--features "$(FEATURES)" \
+		--profile "$(PROFILE)" \
+		$(CARGO_INSTALL_EXTRA_FLAGS)
 
 # The following commands use `cross` to build a cross-compile.
 #
@@ -124,7 +133,7 @@ run-ef-tests:
 test-beacon-chain: $(patsubst %,test-beacon-chain-%,$(FORKS))
 
 test-beacon-chain-%:
-	env FORK_NAME=$* cargo test --release --features fork_from_env -p beacon_chain
+	env FORK_NAME=$* cargo test --release --features fork_from_env,slasher/lmdb -p beacon_chain
 
 # Run the tests in the `operation_pool` crate for all known forks.
 test-op-pool: $(patsubst %,test-op-pool-%,$(FORKS))

beacon_node/Cargo.toml

@@ -36,7 +36,7 @@ clap_utils = { path = "../common/clap_utils" }
 hyper = "0.14.4"
 lighthouse_version = { path = "../common/lighthouse_version" }
 hex = "0.4.2"
-slasher = { path = "../slasher" }
+slasher = { path = "../slasher", default-features = false }
 monitoring_api = { path = "../common/monitoring_api" }
 sensitive_url = { path = "../common/sensitive_url" }
 http_api = { path = "http_api" }

beacon_node/beacon_chain/Cargo.toml

@@ -53,7 +53,7 @@ fork_choice = { path = "../../consensus/fork_choice" }
 task_executor = { path = "../../common/task_executor" }
 derivative = "2.1.1"
 itertools = "0.10.0"
-slasher = { path = "../../slasher" }
+slasher = { path = "../../slasher", default-features = false }
 eth2 = { path = "../../common/eth2" }
 strum = { version = "0.24.0", features = ["derive"] }
 logging = { path = "../../common/logging" }

beacon_node/client/Cargo.toml

@@ -39,7 +39,7 @@ time = "0.3.5"
 directory = {path = "../../common/directory"}
 http_api = { path = "../http_api" }
 http_metrics = { path = "../http_metrics" }
-slasher = { path = "../../slasher" }
+slasher = { path = "../../slasher", default-features = false }
 slasher_service = { path = "../../slasher/service" }
 monitoring_api = {path = "../../common/monitoring_api"}
 execution_layer = { path = "../execution_layer" }

book/src/installation-source.md

@@ -133,6 +133,15 @@ Commonly used features include:
 * `slasher-lmdb`: support for the LMDB slasher backend.
 * `jemalloc`: use [`jemalloc`][jemalloc] to allocate memory. Enabled by default on Linux and macOS.
   Not supported on Windows.
+* `spec-minimal`: support for the minimal preset (useful for testing).
+
+Default features (e.g. `slasher-mdbx`) may be opted out of using the `--no-default-features`
+argument for `cargo`, which can plumbed in via the `CARGO_INSTALL_EXTRA_FLAGS` environment variable.
+E.g.
+
+```
+CARGO_INSTALL_EXTRA_FLAGS="--no-default-features" make
+```
 
 [jemalloc]: https://jemalloc.net/
 

lighthouse/Cargo.toml

@@ -55,7 +55,7 @@ malloc_utils = { path = "../common/malloc_utils" }
 directory = { path = "../common/directory" }
 unused_port = { path = "../common/unused_port" }
 database_manager = { path = "../database_manager" }
-slasher = { path = "../slasher" }
+slasher = { path = "../slasher", default-features = false }
 
 [dev-dependencies]
 tempfile = "3.1.0"

slasher/service/Cargo.toml

@@ -9,7 +9,7 @@ beacon_chain = { path = "../../beacon_node/beacon_chain" }
 directory = { path = "../../common/directory" }
 lighthouse_network = { path = "../../beacon_node/lighthouse_network" }
 network = { path = "../../beacon_node/network" }
-slasher = { path = ".." }
+slasher = { path = "..", default-features = false }
 slog = "2.5.2"
 slot_clock = { path = "../../common/slot_clock" }
 state_processing = { path = "../../consensus/state_processing" }