distinguish between native and web in signer

signer/Cargo.toml

@@ -15,7 +15,7 @@ description = "Sign extrinsics to be submitted by Subxt"
 keywords = ["parity", "subxt", "extrinsic", "signer"]
 
 [features]
-default = ["sr25519", "ecdsa", "subxt"]
+default = ["sr25519", "ecdsa", "subxt", "native"]
 
 # Pick the signer implementation(s) you need by enabling the
 # corresponding features. Note: I had more difficulties getting
@@ -30,11 +30,12 @@ subxt = ["dep:subxt"]
 
 # The getrandom package is used via schnorrkel. We need to enable the JS
 # feature on it if compiling for the web.
-web = ["getrandom/js"]
+web = ["getrandom/js", "subxt?/web"]
+native = ["subxt?/native"]
 
 [dependencies]
+subxt = { workspace = true, optional = true, default-features = false }
 regex = { workspace = true }
-subxt = { workspace = true, optional = true }
 hex = { workspace = true }
 codec = { package = "parity-scale-codec", workspace = true, features = ["derive"] }
 sp-core-hashing = { workspace = true }

signer/src/lib.rs

@@ -38,3 +38,8 @@ pub use secrecy::{ExposeSecret, SecretString};
 // SecretUri's can be parsed from strings and used to generate key pairs.
 // DeriveJunctions are the "path" part of these SecretUris.
 pub use crypto::{DeriveJunction, SecretUri, SecretUriError, DEV_PHRASE};
+
+#[cfg(all(
+    feature = "subxt", not(any(feature = "web", feature = "native"))
+))]
+compile_error!("subxt-signer: When using the 'subxt' feature, exactly one of the 'web' and 'native' features should be used.");