From d6284dc6f4ac678ed6da43ec9d3528ccd0ce2c25 Mon Sep 17 00:00:00 2001
From: Mark Toda <toda.mark@gmail.com>
Date: Sat, 4 Apr 2020 13:00:13 -0700
Subject: [PATCH] Use serde_json to export hardcoded sync

The exported hardcoded sync was previously generating invalid JSON, with
the CHT list ending in a trailing comma. In order to remedy this, this
commit uses serde_json to serialize the SpecHardcodedSync struct
into valid JSON.

Fixes #11415
---
 Cargo.lock               |  2 ++
 ethcore/spec/Cargo.toml  |  2 ++
 ethcore/spec/src/spec.rs | 32 ++++++++++++++++++++++++--------
 3 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index 6ac24a5d0e0..f9f97558e3c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4782,6 +4782,8 @@ dependencies = [
  "parity-bytes",
  "pod",
  "rlp",
+ "serde",
+ "serde_json",
  "tempfile",
  "trace",
  "trie-vm-factories",
diff --git a/ethcore/spec/Cargo.toml b/ethcore/spec/Cargo.toml
index 1c17d0cc0e2..e99d48f8238 100644
--- a/ethcore/spec/Cargo.toml
+++ b/ethcore/spec/Cargo.toml
@@ -32,6 +32,8 @@ maplit = "1"
 null-engine = { path = "../engines/null-engine" }
 pod = { path = "../pod" }
 rlp = "0.4.2"
+serde = "1.0"
+serde_json = "1.0"
 trace = { path = "../trace" }
 trie-vm-factories = { path = "../trie-vm-factories" }
 vm = { path = "../vm" }
diff --git a/ethcore/spec/src/spec.rs b/ethcore/spec/src/spec.rs
index 507082cb06f..5a1938b4353 100644
--- a/ethcore/spec/src/spec.rs
+++ b/ethcore/spec/src/spec.rs
@@ -51,6 +51,8 @@ use maplit::btreeset;
 use null_engine::NullEngine;
 use pod::PodState;
 use rlp::{Rlp, RlpStream};
+use serde::ser::{Serialize, Serializer, SerializeStruct};
+use serde_json;
 use trace::{NoopTracer, NoopVMTracer};
 use trie_vm_factories::Factories;
 use vm::{EnvInfo, ActionType, ActionValue, ActionParams, ParamsType};
@@ -264,15 +266,29 @@ impl From<ethjson::spec::HardcodedSync> for SpecHardcodedSync {
 	}
 }
 
+impl Serialize for SpecHardcodedSync {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where
+            S: Serializer,
+        {
+            let mut serialized = serializer.serialize_struct("SpecHardcodedSync", 3)?;
+
+            let header_str = format!("{:x}", self.header);
+            serialized.serialize_field("header", &header_str)?;
+
+            let total_difficulty_str = format!("{:?}", self.total_difficulty);
+            serialized.serialize_field("totalDifficulty", &total_difficulty_str)?;
+
+            serialized.serialize_field("CHTs", &self.chts)?;
+            serialized.end()
+        }
+}
+
 impl fmt::Display for SpecHardcodedSync {
-	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-		writeln!(f, "{{")?;
-		writeln!(f, r#""header": "{:x}","#, self.header)?;
-		writeln!(f, r#""totalDifficulty": "{:?}""#, self.total_difficulty)?;
-		// TODO: #11415 - fix trailing comma for CHTs
-		writeln!(f, r#""CHTs": {:#?}"#, self.chts.iter().map(|x| format!("{:?}", x)).collect::<Vec<_>>())?;
-		writeln!(f, "}}")
-	}
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let serialized = serde_json::to_string_pretty(&self).unwrap();
+        writeln!(f, "{}", serialized)
+    }
 }
 
 fn convert_json_to_spec(