Better no-std support

- Use `default-features = false` for `miniscript`,`bitcoin`,and `bdk_chain`
- Introduce `bdk_chain/std` feature
- Add GitHub workflow `check-no-std` (not yet completly working)
- Update GitHub workflow `check-wasm` to disable default `std` features

crates/bdk/Cargo.toml

@@ -15,11 +15,11 @@ rust-version = "1.57"
 [dependencies]
 log = "=0.4.18"
 rand = "^0.8"
-miniscript = { version = "9", features = ["serde"] }
-bitcoin = { version = "0.29", features = ["serde", "base64", "rand"] }
+miniscript = { version = "9", features = ["serde"], default-features = false }
+bitcoin = { version = "0.29", features = ["serde", "base64", "rand"], default-features = false }
 serde = { version = "^1.0", features = ["derive"] }
 serde_json = { version = "^1.0" }
-bdk_chain = { path = "../chain", version = "0.4.0", features = ["miniscript", "serde"] }
+bdk_chain = { path = "../chain", version = "0.4.0", features = ["miniscript", "serde"], default-features = false }
 
 # Optional dependencies
 hwi = { version = "0.5", optional = true, features = [ "use-miniscript"] }
@@ -29,17 +29,15 @@ bip39 = { version = "1.0.1", optional = true }
 getrandom = "0.2"
 js-sys = "0.3"
 
-
 [features]
 default = ["std"]
-std = []
+std = ["bitcoin/std", "miniscript/std", "bdk_chain/std"]
 compiler = ["miniscript/compiler"]
 all-keys = ["keys-bip39"]
 keys-bip39 = ["bip39"]
 hardware-signer = ["hwi"]
 test-hardware-signer = ["hardware-signer"]
 
-
 # This feature is used to run `cargo check` in our CI targeting wasm. It's not recommended
 # for libraries to explicitly include the "getrandom/js" feature, so we only do it when
 # necessary for running our CI. See: https://docs.rs/getrandom/0.2.8/getrandom/#webassembly-support
@@ -52,12 +50,10 @@ env_logger = "0.7"
 base64 = "^0.13"
 assert_matches = "1.5.0"
 
-
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
-
 [[example]]
 name = "mnemonic_to_descriptors"
 path = "examples/mnemonic_to_descriptors.rs"

crates/bdk/src/descriptor/error.rs

@@ -11,6 +11,8 @@
 
 //! Descriptor errors
 
+use core::fmt;
+
 /// Errors related to the parsing and usage of descriptors
 #[derive(Debug)]
 pub enum Error {
@@ -51,8 +53,8 @@ impl From<crate::keys::KeyError> for Error {
     }
 }
 
-impl std::fmt::Display for Error {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::InvalidHdKeyPath => write!(f, "Invalid HD key path"),
             Self::InvalidDescriptorChecksum => {

crates/bdk/src/error.rs

@@ -107,8 +107,10 @@ impl fmt::Display for MiniscriptPsbtError {
     }
 }
 
+#[cfg(feature = "std")]
 impl std::error::Error for MiniscriptPsbtError {}
 
+#[cfg(feature = "std")]
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {

crates/bdk/src/keys/mod.rs

@@ -15,6 +15,7 @@ use crate::collections::HashSet;
 use alloc::string::{String, ToString};
 use alloc::vec::Vec;
 use core::any::TypeId;
+use core::fmt;
 use core::marker::PhantomData;
 use core::ops::Deref;
 use core::str::FromStr;
@@ -934,8 +935,8 @@ pub enum KeyError {
 impl_error!(miniscript::Error, Miniscript, KeyError);
 impl_error!(bitcoin::util::bip32::Error, Bip32, KeyError);
 
-impl std::fmt::Display for KeyError {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+impl fmt::Display for KeyError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             Self::InvalidScriptContext => write!(f, "Invalid script context"),
             Self::InvalidNetwork => write!(f, "Invalid network"),

crates/bdk/src/wallet/mod.rs

@@ -170,9 +170,9 @@ pub enum NewError<P> {
     Persist(P),
 }
 
-impl<P> core::fmt::Display for NewError<P>
+impl<P> fmt::Display for NewError<P>
 where
-    P: core::fmt::Display,
+    P: fmt::Display,
 {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {