From 46bedb3282aa3386cbf7b5ba81820041d86dabd1 Mon Sep 17 00:00:00 2001
From: Georgios Konstantopoulos <me@gakonst.com>
Date: Sat, 30 Oct 2021 21:27:17 +0300
Subject: [PATCH] feat: only compile changed files (#544)

---
 ethers-solc/src/cache.rs | 14 +++++++++++---
 ethers-solc/src/lib.rs   | 12 ++++++++----
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/ethers-solc/src/cache.rs b/ethers-solc/src/cache.rs
index 0a1ecaa3..ae12591f 100644
--- a/ethers-solc/src/cache.rs
+++ b/ethers-solc/src/cache.rs
@@ -58,9 +58,17 @@ impl SolFilesCache {
         self.files.retain(|file, _| Path::new(file).exists())
     }
 
-    /// Returns if true if a source has changed and false if no source has changed
-    pub fn is_changed(&self, sources: &Sources, config: Option<&SolcConfig>) -> bool {
-        sources.iter().any(|(file, source)| self.has_changed(file, source.content_hash(), config))
+    /// Returns only the files that were changed from the provided sources, to save time
+    /// when compiling.
+    pub fn get_changed_files<'a>(
+        &'a self,
+        sources: Sources,
+        config: Option<&'a SolcConfig>,
+    ) -> Sources {
+        sources
+            .into_iter()
+            .filter(move |(file, source)| self.has_changed(file, source.content_hash(), config))
+            .collect()
     }
 
     /// Returns true if the given content hash or config differs from the file's
diff --git a/ethers-solc/src/lib.rs b/ethers-solc/src/lib.rs
index bfcf9cb5..5b873449 100644
--- a/ethers-solc/src/lib.rs
+++ b/ethers-solc/src/lib.rs
@@ -105,13 +105,17 @@ impl Project {
             source_name_path.insert(import, path);
         }
 
-        if self.cached && self.paths.cache.exists() {
-            // check anything changed
+        // If there's a cache set, filter to only re-compile the files which were changed
+        let sources = if self.cached && self.paths.cache.exists() {
             let cache = SolFilesCache::read(&self.paths.cache)?;
-            if !cache.is_changed(&sources, Some(&self.solc_config)) {
+            let changed_files = cache.get_changed_files(sources, Some(&self.solc_config));
+            if changed_files.is_empty() {
                 return Ok(ProjectCompileOutput::Unchanged)
             }
-        }
+            changed_files
+        } else {
+            sources
+        };
 
         // replace absolute path with source name to make solc happy
         let sources = apply_mappings(sources, path_source_name);