Optional serde for phragmen support (#3994)

* Add serde to phragmen

* Update lock file

* and bump a version

* and bump a version again

* Apply suggestions from code review

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* revert impl-tarit for tuple update

* revert session.

* Revert "revert session."

This reverts commit 98086c9db56677068db85f74320868b2c10d1c00.

* Revert "revert impl-tarit for tuple update"

This reverts commit 28a7fddee2e09c5785b19883f743065e0be8f331.

substrate/core/chain-spec/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2018"
 
 [dependencies]
 substrate-chain-spec-derive = { path = "./derive" }
-impl-trait-for-tuples = "0.1.2"
+impl-trait-for-tuples = "0.1.3"
 network = { package = "substrate-network", path = "../../core/network" }
 primitives = { package = "substrate-primitives", path = "../primitives" }
 serde = { version = "1.0.101", features = ["derive"] }

substrate/core/phragmen/Cargo.toml

@@ -5,8 +5,9 @@ authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-sr-primitives = { path = "../sr-primitives", default-features = false }
+serde = { version = "1.0.101", optional = true, features = ["derive"] }
 rstd = { package = "sr-std", path = "../sr-std", default-features = false }
+sr-primitives = { path = "../sr-primitives", default-features = false }
 
 [dev-dependencies]
 runtime-io ={ package = "sr-io", path = "../sr-io" }
@@ -16,6 +17,7 @@ rand = "0.7.2"
 [features]
 default = ["std"]
 std = [
+	"serde",
 	"rstd/std",
 	"sr-primitives/std",
 ]

substrate/core/phragmen/src/lib.rs

@@ -116,6 +116,7 @@ pub struct PhragmenResult<AccountId> {
 /// This, at the current version, resembles the `Exposure` defined in the staking SRML module, yet
 /// they do not necessarily have to be the same.
 #[derive(Default, RuntimeDebug)]
+#[cfg_attr(feature = "std", derive(serde::Serialize, serde::Deserialize))]
 pub struct Support<AccountId> {
 	/// The amount of support as the effect of self-vote.
 	pub own: ExtendedBalance,

substrate/core/sr-primitives/Cargo.toml

@@ -15,7 +15,7 @@ runtime_io = { package = "sr-io", path = "../sr-io", default-features = false }
 log = { version = "0.4.8", optional = true }
 paste = "0.1.6"
 rand = { version = "0.7.2", optional = true }
-impl-trait-for-tuples = "0.1.2"
+impl-trait-for-tuples = "0.1.3"
 
 [dev-dependencies]
 serde_json = "1.0.41"