perf(solc): wrap source content in Arc (#2138)

ethers-solc/Cargo.toml

@@ -18,7 +18,7 @@ keywords = ["ethereum", "web3", "solc", "solidity", "ethers"]
 [dependencies]
 ethers-core = { version = "^1.0.0", path = "../ethers-core", default-features = false }
 serde_json = "1.0.68"
-serde = { version = "1.0.130", features = ["derive"] }
+serde = { version = "1.0.130", features = ["derive", "rc"] }
 semver = { version = "1.0.16", features = ["serde"] }
 walkdir = "2.3.2"
 tokio = { version = "1.18", default-features = false, features = ["rt"] }

ethers-solc/src/artifacts/mod.rs

@@ -11,6 +11,7 @@ use std::{
     fmt, fs,
     path::{Path, PathBuf},
     str::FromStr,
+    sync::Arc,
 };
 use tracing::warn;
 use yansi::Paint;
@@ -1195,16 +1196,29 @@ pub struct DocLibraries {
     pub libs: BTreeMap<String, serde_json::Value>,
 }
 
+/// Content of a solidity file
+///
+/// This contains the actual source code of a file
 #[derive(Clone, Debug, Serialize, Deserialize, Eq, PartialEq)]
 pub struct Source {
-    pub content: String,
+    /// Content of the file
+    ///
+    /// This is an `Arc` because it may be cloned. If the [Graph](crate::resolver::Graph) of the
+    /// project contains multiple conflicting versions then the same [Source] may be required by
+    /// conflicting versions and needs to be duplicated.
+    pub content: Arc<String>,
 }
 
 impl Source {
-    /// Reads the file content
+    /// Creates a new instance of [Source] with the given content.
+    pub fn new(content: impl Into<String>) -> Self {
+        Self { content: Arc::new(content.into()) }
+    }
+
+    /// Reads the file's content
     pub fn read(file: impl AsRef<Path>) -> Result<Self, SolcIoError> {
         let file = file.as_ref();
-        Ok(Self { content: fs::read_to_string(file).map_err(|err| SolcIoError::new(err, file))? })
+        Ok(Self::new(fs::read_to_string(file).map_err(|err| SolcIoError::new(err, file))?))
     }
 
     /// Recursively finds all source files under the given dir path and reads them all
@@ -1254,7 +1268,7 @@ impl Source {
     /// Generate a non-cryptographically secure checksum of the file's content
     pub fn content_hash(&self) -> String {
         let mut hasher = md5::Md5::new();
-        hasher.update(&self.content);
+        hasher.update(self);
         let result = hasher.finalize();
         hex::encode(result)
     }
@@ -1270,11 +1284,9 @@ impl Source {
     /// async version of `Self::read`
     pub async fn async_read(file: impl AsRef<Path>) -> Result<Self, SolcIoError> {
         let file = file.as_ref();
-        Ok(Self {
-            content: tokio::fs::read_to_string(file)
-                .await
-                .map_err(|err| SolcIoError::new(err, file))?,
-        })
+        Ok(Self::new(
+            tokio::fs::read_to_string(file).await.map_err(|err| SolcIoError::new(err, file))?,
+        ))
     }
 
     /// Finds all source files under the given dir path and reads them all
@@ -1306,6 +1318,12 @@ impl AsRef<str> for Source {
     }
 }
 
+impl AsRef<[u8]> for Source {
+    fn as_ref(&self) -> &[u8] {
+        self.content.as_bytes()
+    }
+}
+
 /// Output type `solc` produces
 #[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Default)]
 pub struct CompilerOutput {

ethers-solc/src/buildinfo.rs

@@ -104,7 +104,7 @@ mod tests {
     fn build_info_serde() {
         let inputs = CompilerInput::with_sources(BTreeMap::from([(
             PathBuf::from("input.sol"),
-            Source { content: "".to_string() },
+            Source::new(""),
         )]));
         let output = CompilerOutput::default();
         let v: Version = "0.8.4+commit.c7e474f2".parse().unwrap();

ethers-solc/src/compile/mod.rs

@@ -909,6 +909,6 @@ mod tests {
     ///// helpers
 
     fn source(version: &str) -> Source {
-        Source { content: format!("pragma solidity {version};\n") }
+        Source::new(format!("pragma solidity {version};\n"))
     }
 }