fix(solc): proper metadata deserialization

ethers-solc/src/artifacts/contract.rs

@@ -4,7 +4,8 @@ use crate::artifacts::{
     bytecode::{
         Bytecode, BytecodeObject, CompactBytecode, CompactDeployedBytecode, DeployedBytecode,
     },
-    DevDoc, Evm, Ewasm, LosslessAbi, LosslessMetadata, Offsets, StorageLayout, UserDoc,
+    serde_helpers, DevDoc, Evm, Ewasm, LosslessAbi, LosslessMetadata, Offsets, StorageLayout,
+    UserDoc,
 };
 use ethers_core::{abi::Contract as Abi, types::Bytes};
 use serde::{Deserialize, Serialize};
@@ -17,7 +18,11 @@ pub struct Contract {
     /// The Ethereum Contract Metadata.
     /// See <https://docs.soliditylang.org/en/develop/metadata.html>
     pub abi: Option<LosslessAbi>,
-    #[serde(default, skip_serializing_if = "Option::is_none")]
+    #[serde(
+        default,
+        skip_serializing_if = "Option::is_none",
+        with = "serde_helpers::json_string_opt"
+    )]
     pub metadata: Option<LosslessMetadata>,
     #[serde(default)]
     pub userdoc: UserDoc,

ethers-solc/src/artifacts/mod.rs

@@ -889,9 +889,25 @@ impl<'de> Deserialize<'de> for LosslessMetadata {
     where
         D: Deserializer<'de>,
     {
-        let raw_metadata = String::deserialize(deserializer)?;
-        let metadata = serde_json::from_str(&raw_metadata).map_err(serde::de::Error::custom)?;
-        Ok(Self { raw_metadata, metadata })
+        struct LosslessMetadataVisitor;
+
+        impl<'de> Visitor<'de> for LosslessMetadataVisitor {
+            type Value = LosslessMetadata;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
+                write!(formatter, "metadata string")
+            }
+
+            fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
+            where
+                E: serde::de::Error,
+            {
+                let raw_metadata = value.to_string();
+                let metadata = serde_json::from_str(value).map_err(serde::de::Error::custom)?;
+                Ok(LosslessMetadata { raw_metadata, metadata })
+            }
+        }
+        deserializer.deserialize_str(LosslessMetadataVisitor)
     }
 }
 

ethers-solc/src/artifacts/serde_helpers.rs

@@ -66,8 +66,8 @@ pub mod json_string_opt {
             if s.is_empty() {
                 return Ok(None)
             }
-
-            serde_json::from_str(&s).map_err(de::Error::custom).map(Some)
+            let value = serde_json::Value::String(s);
+            serde_json::from_value(value).map_err(de::Error::custom).map(Some)
         } else {
             Ok(None)
         }