Drop the no-std feature from lightning-invoice

Now that we don't have to have everything in our entire ecosystem
use the same `std`/`no-std` feature combinations we should start by
untangling our own features a bit.

This takes another step by removing the `no-std` feature entirely
from the `lightning-invoice` crate and removing all feature
implications on dependencies from the remaining `std` feature.

Author: TheBlueMatt

ci/ci-tests.sh

@@ -74,14 +74,21 @@ grep '^max_level_' lightning/Cargo.toml | awk '{ print $1 }'| while read -r FEAT
 	RUSTFLAGS="$RUSTFLAGS -A unused_variables -A unused_macros -A unused_imports -A dead_code" cargo check -p lightning --verbose --color always --features "$FEATURE"
 done
 
+echo -e "\n\nTesting no-std builds"
+for DIR in lightning-invoice lightning-background-processor; do
+	cargo test -p $DIR --verbose --color always --no-default-features
+	# check if there is a conflict between no-std and the c_bindings cfg
+	RUSTFLAGS="$RUSTFLAGS --cfg=c_bindings" cargo test -p $DIR --verbose --color always --no-default-features
+done
+
 echo -e "\n\nTesting no-std flags in various combinations"
-for DIR in lightning lightning-invoice lightning-rapid-gossip-sync; do
+for DIR in lightning lightning-rapid-gossip-sync; do
 	cargo test -p $DIR --verbose --color always --no-default-features --features no-std
 	# check if there is a conflict between no-std and the default std feature
 	cargo test -p $DIR --verbose --color always --features no-std
 done
 
-for DIR in lightning lightning-invoice lightning-rapid-gossip-sync; do
+for DIR in lightning lightning-rapid-gossip-sync; do
 	# check if there is a conflict between no-std and the c_bindings cfg
 	RUSTFLAGS="$RUSTFLAGS --cfg=c_bindings" cargo test -p $DIR --verbose --color always --no-default-features --features=no-std
 done
@@ -91,7 +98,7 @@ RUSTFLAGS="$RUSTFLAGS --cfg=c_bindings" cargo test --verbose --color always
 cargo test -p lightning --verbose --color always --no-default-features --features=std,_test_vectors
 # This one only works for lightning-invoice
 # check that compile with no-std and serde works in lightning-invoice
-cargo test -p lightning-invoice --verbose --color always --no-default-features --features no-std --features serde
+cargo test -p lightning-invoice --verbose --color always --no-default-features --features serde
 
 echo -e "\n\nTesting no-std build on a downstream no-std crate"
 # check no-std compatibility across dependencies

lightning-invoice/Cargo.toml

@@ -15,9 +15,7 @@ all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
 [features]
-default = ["std"]
-no-std = []
-std = ["bech32/std"]
+std = []
 
 [dependencies]
 bech32 = { version = "0.9.1", default-features = false }

lightning-invoice/src/lib.rs

@@ -22,9 +22,6 @@
 //!
 //! [`Bolt11Invoice::from_str`]: crate::Bolt11Invoice#impl-FromStr
 
-#[cfg(not(any(feature = "std", feature = "no-std")))]
-compile_error!("at least one of the `std` or `no-std` features must be enabled");
-
 extern crate bech32;
 extern crate lightning_types;
 extern crate alloc;

lightning/Cargo.toml

@@ -31,8 +31,8 @@ unsafe_revoked_tx_signing = []
 # Override signing to not include randomness when generating signatures for test vectors.
 _test_vectors = []
 
-no-std = ["hashbrown", "possiblyrandom", "lightning-invoice/no-std", "libm"]
-std = ["lightning-invoice/std", "bech32/std"]
+no-std = ["hashbrown", "possiblyrandom", "libm"]
+std = ["bech32/std"]
 
 # Generates low-r bitcoin signatures, which saves 1 byte in 50% of the cases
 grind_signatures = []