From 205ddec344e0e4500e97571d6ce972b34b3e9189 Mon Sep 17 00:00:00 2001
From: Gavin Wood <gavin@parity.io>
Date: Sun, 22 Dec 2019 23:11:34 +0100
Subject: [PATCH] Twitter field for IdentityInfo (in a back-compat way) (#4476)

---
 substrate/frame/identity/src/lib.rs        | 31 +++++++++++++--
 substrate/primitives/runtime/src/traits.rs | 46 ++++++++++++++++++++++
 2 files changed, 74 insertions(+), 3 deletions(-)

diff --git a/substrate/frame/identity/src/lib.rs b/substrate/frame/identity/src/lib.rs
index 3fda978b13..1e98e60b5e 100644
--- a/substrate/frame/identity/src/lib.rs
+++ b/substrate/frame/identity/src/lib.rs
@@ -69,7 +69,8 @@ use sp_std::prelude::*;
 use sp_std::{fmt::Debug, ops::Add, iter::once};
 use enumflags2::BitFlags;
 use codec::{Encode, Decode};
-use sp_runtime::{DispatchResult, traits::{StaticLookup, EnsureOrigin, Zero}, RuntimeDebug};
+use sp_runtime::{DispatchResult, RuntimeDebug};
+use sp_runtime::traits::{StaticLookup, EnsureOrigin, Zero, AppendZerosInput};
 use frame_support::{
 	decl_module, decl_event, decl_storage, ensure, decl_error,
 	traits::{Currency, ReservableCurrency, OnUnbalanced, Get},
@@ -246,6 +247,7 @@ pub enum IdentityField {
 	Email          = 0b0000000000000000000000000000000000000000000000000000000000010000,
 	PgpFingerprint = 0b0000000000000000000000000000000000000000000000000000000000100000,
 	Image          = 0b0000000000000000000000000000000000000000000000000000000001000000,
+	Twitter        = 0b0000000000000000000000000000000000000000000000000000000010000000,
 }
 
 /// Wrapper type for `BitFlags<IdentityField>` that implements `Codec`.
@@ -296,7 +298,7 @@ pub struct IdentityInfo {
 	/// Stored as UTF-8.
 	pub web: Data,
 
-	/// The Riot handle held by the controller of the account.
+	/// The Riot/Matrix handle held by the controller of the account.
 	///
 	/// Stored as UTF-8.
 	pub riot: Data,
@@ -312,6 +314,9 @@ pub struct IdentityInfo {
 	/// A graphic image representing the controller of the account. Should be a company,
 	/// organization or project logo or a headshot in the case of a human.
 	pub image: Data,
+
+	/// The Twitter identity. The leading `@` character may be elided.
+	pub twitter: Data,
 }
 
 /// Information concerning the identity of the controller of an account.
@@ -344,7 +349,7 @@ impl <
 }
 
 /// Information concerning a registrar.
-#[derive(Clone, Encode, Decode, Eq, PartialEq, RuntimeDebug)]
+#[derive(Clone, Encode, Eq, PartialEq, RuntimeDebug)]
 pub struct RegistrarInfo<
 	Balance: Encode + Decode + Clone + Debug + Eq + PartialEq,
 	AccountId: Encode + Decode + Clone + Debug + Eq + PartialEq
@@ -360,6 +365,16 @@ pub struct RegistrarInfo<
 	pub fields: IdentityFields,
 }
 
+impl<
+	Balance: Encode + Decode + Clone + Debug + Eq + PartialEq,
+	AccountId: Encode + Decode + Clone + Debug + Eq + PartialEq
+> Decode for RegistrarInfo<Balance, AccountId> {
+	fn decode<I: codec::Input>(input: &mut I) -> sp_std::result::Result<Self, codec::Error> {
+		let (account, fee, fields) = Decode::decode(&mut AppendZerosInput::new(input))?;
+		Ok(Self { account, fee, fields })
+	}
+}
+
 decl_storage! {
 	trait Store for Module<T: Trait> as Sudo {
 		/// Information that is pertinent to identify the entity behind an account.
@@ -958,6 +973,16 @@ mod tests {
 		}
 	}
 
+	#[test]
+	fn trailing_zeros_decodes_into_default_data() {
+		let encoded = Data::Raw(b"Hello".to_vec()).encode();
+		assert!(<(Data, Data)>::decode(&mut &encoded[..]).is_err());
+		let input = &mut &encoded[..];
+		let (a, b) = <(Data, Data)>::decode(&mut AppendZerosInput::new(input)).unwrap();
+		assert_eq!(a, Data::Raw(b"Hello".to_vec()));
+		assert_eq!(b, Data::None);
+	}
+
 	#[test]
 	fn adding_registrar_should_work() {
 		new_test_ext().execute_with(|| {
diff --git a/substrate/primitives/runtime/src/traits.rs b/substrate/primitives/runtime/src/traits.rs
index 22cd2814e7..a40cd35882 100644
--- a/substrate/primitives/runtime/src/traits.rs
+++ b/substrate/primitives/runtime/src/traits.rs
@@ -999,6 +999,52 @@ pub trait OpaqueKeys: Clone {
 	fn ownership_proof_is_valid(&self, _proof: &[u8]) -> bool { true }
 }
 
+/// Input that adds infinite number of zero after wrapped input.
+///
+/// This can add an infinite stream of zeros onto any input, not just a slice as with
+/// `TrailingZerosInput`.
+pub struct AppendZerosInput<'a, T>(&'a mut T);
+
+impl<'a, T> AppendZerosInput<'a, T> {
+	/// Create a new instance from the given byte array.
+	pub fn new(input: &'a mut T) -> Self {
+		Self(input)
+	}
+}
+
+impl<'a, T: codec::Input> codec::Input for AppendZerosInput<'a, T> {
+	fn remaining_len(&mut self) -> Result<Option<usize>, codec::Error> {
+		Ok(None)
+	}
+
+	fn read(&mut self, into: &mut [u8]) -> Result<(), codec::Error> {
+		let remaining = self.0.remaining_len()?;
+		let completed = if let Some(n) = remaining {
+			let readable = into.len().min(n);
+			// this should never fail if `remaining_len` API is implemented correctly.
+			self.0.read(&mut into[..readable])?;
+			readable
+		} else {
+			// Fill it byte-by-byte.
+			let mut i = 0;
+			while i < into.len() {
+				if let Ok(b) = self.0.read_byte() {
+					into[i] = b;
+					i += 1;
+				} else {
+					break;
+				}
+			}
+			i
+		};
+		// Fill the rest with zeros.
+		for i in &mut into[completed..] {
+			*i = 0;
+		}
+		Ok(())
+	}
+}
+
 /// Input that adds infinite number of zero after wrapped input.
 pub struct TrailingZeroInput<'a>(&'a [u8]);