Support for keyring in runtimes (#2044)

This functionality is required for #1984.

This PR enables
[`sp-keyring`](https://github.com/paritytech/polkadot-sdk/blob/21d36b7b4229c4d5225944f197918cde23fda4ea/substrate/primitives/keyring/src/sr25519.rs#L31-L40)
in `no-std` environments, allowing to generate the public key (e.g.
`AccountKeyring::Alice.public().to_ss58check()`), which can be later
used in the any of built-in [_runtime-genesis-config_
variant](https://github.com/paritytech/polkadot-sdk/blob/21d36b7b4229c4d5225944f197918cde23fda4ea/polkadot/node/service/src/chain_spec.rs#L1066-L1073).


The proposal is as follows:
- expose [`core::Pair`
trait](https://github.com/paritytech/polkadot-sdk/blob/d6f15306282e3de848a09c9aa9cba6f95a7811f0/substrate/primitives/core/src/crypto.rs#L832)
in `no-std`,
- `full_crypto` feature enables `sign` method,
- `std` feature enables `generate_with_phrase` and `generate` methods
(randomness is required),
- All other functionality, currently gated by `full_crypto` will be
available unconditionally (`no-std`):
-- `from_string`
-- `from_string_with_seed`
-- `from seed`
-- `from_seed_slice`
-- `from_phrase`
-- `derive`
-- `verify`

---

Depends on https://github.com/rust-bitcoin/rust-bip39/pull/57

---------

Co-authored-by: command-bot <>
Co-authored-by: Davide Galassi <davxy@datawok.net>

substrate/primitives/keyring/src/bandersnatch.rs

@@ -18,14 +18,21 @@
 //! A set of well-known keys used for testing.
 
 pub use sp_core::bandersnatch;
+#[cfg(feature = "std")]
+use sp_core::bandersnatch::Signature;
 use sp_core::{
-	bandersnatch::{Pair, Public, Signature},
+	bandersnatch::{Pair, Public},
 	crypto::UncheckedFrom,
 	hex2array, ByteArray, Pair as PairT,
 };
 
+extern crate alloc;
+use alloc::{fmt, format, str::FromStr, string::String, vec::Vec};
+
 /// Set of test accounts.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, strum::Display, strum::EnumIter)]
+#[derive(
+	Debug, Clone, Copy, PartialEq, Eq, Hash, strum::Display, strum::EnumIter, Ord, PartialOrd,
+)]
 pub enum Keyring {
 	Alice,
 	Bob,
@@ -56,6 +63,7 @@ impl Keyring {
 		Public::from(self).to_raw_vec()
 	}
 
+	#[cfg(feature = "std")]
 	pub fn sign(self, msg: &[u8]) -> Signature {
 		Pair::from(self).sign(msg)
 	}
@@ -102,16 +110,16 @@ impl From<Keyring> for &'static str {
 #[derive(Debug)]
 pub struct ParseKeyringError;
 
-impl std::fmt::Display for ParseKeyringError {
-	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+impl fmt::Display for ParseKeyringError {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 		write!(f, "ParseKeyringError")
 	}
 }
 
-impl std::str::FromStr for Keyring {
+impl FromStr for Keyring {
 	type Err = ParseKeyringError;
 
-	fn from_str(s: &str) -> Result<Self, <Self as std::str::FromStr>::Err> {
+	fn from_str(s: &str) -> Result<Self, <Self as FromStr>::Err> {
 		match s {
 			"Alice" => Ok(Keyring::Alice),
 			"Bob" => Ok(Keyring::Bob),

substrate/primitives/keyring/src/ed25519.rs

@@ -18,14 +18,21 @@
 //! Support code for the runtime. A set of test accounts.
 
 pub use sp_core::ed25519;
+#[cfg(feature = "std")]
+use sp_core::ed25519::Signature;
 use sp_core::{
-	ed25519::{Pair, Public, Signature},
+	ed25519::{Pair, Public},
 	hex2array, ByteArray, Pair as PairT, H256,
 };
 use sp_runtime::AccountId32;
 
+extern crate alloc;
+use alloc::{format, string::String, vec::Vec};
+
 /// Set of test accounts.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, strum::Display, strum::EnumIter)]
+#[derive(
+	Debug, Clone, Copy, PartialEq, Eq, Hash, strum::Display, strum::EnumIter, Ord, PartialOrd,
+)]
 pub enum Keyring {
 	Alice,
 	Bob,
@@ -76,6 +83,7 @@ impl Keyring {
 		self.to_raw_public().into()
 	}
 
+	#[cfg(feature = "std")]
 	pub fn sign(self, msg: &[u8]) -> Signature {
 		Pair::from(self).sign(msg)
 	}

substrate/primitives/keyring/src/lib.rs

@@ -17,6 +17,8 @@
 
 //! Support code for the runtime. A set of test accounts.
 
+#![cfg_attr(not(feature = "std"), no_std)]
+
 /// Test account crypto for sr25519.
 pub mod sr25519;
 

substrate/primitives/keyring/src/sr25519.rs

@@ -18,15 +18,22 @@
 //! Support code for the runtime. A set of test accounts.
 
 pub use sp_core::sr25519;
+#[cfg(feature = "std")]
+use sp_core::sr25519::Signature;
 use sp_core::{
 	hex2array,
-	sr25519::{Pair, Public, Signature},
+	sr25519::{Pair, Public},
 	ByteArray, Pair as PairT, H256,
 };
 use sp_runtime::AccountId32;
 
+extern crate alloc;
+use alloc::{fmt, format, str::FromStr, string::String, vec::Vec};
+
 /// Set of test accounts.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, strum::Display, strum::EnumIter)]
+#[derive(
+	Debug, Clone, Copy, PartialEq, Eq, Hash, strum::Display, strum::EnumIter, Ord, PartialOrd,
+)]
 pub enum Keyring {
 	Alice,
 	Bob,
@@ -77,6 +84,7 @@ impl Keyring {
 		self.to_raw_public().into()
 	}
 
+	#[cfg(feature = "std")]
 	pub fn sign(self, msg: &[u8]) -> Signature {
 		Pair::from(self).sign(msg)
 	}
@@ -140,16 +148,16 @@ impl From<Keyring> for sp_runtime::MultiSigner {
 #[derive(Debug)]
 pub struct ParseKeyringError;
 
-impl std::fmt::Display for ParseKeyringError {
-	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+impl fmt::Display for ParseKeyringError {
+	fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 		write!(f, "ParseKeyringError")
 	}
 }
 
-impl std::str::FromStr for Keyring {
+impl FromStr for Keyring {
 	type Err = ParseKeyringError;
 
-	fn from_str(s: &str) -> Result<Self, <Self as std::str::FromStr>::Err> {
+	fn from_str(s: &str) -> Result<Self, <Self as FromStr>::Err> {
 		match s {
 			"alice" => Ok(Keyring::Alice),
 			"bob" => Ok(Keyring::Bob),