feat(solc): report on unresolved imports (#905)

* chore: fix unused import warning

* feat: add additional report message

ethers-solc/src/compile/mod.rs

@@ -42,15 +42,12 @@ pub const BERLIN_SOLC: Version = Version::new(0, 8, 5);
 /// https://blog.soliditylang.org/2021/08/11/solidity-0.8.7-release-announcement/
 pub const LONDON_SOLC: Version = Version::new(0, 8, 7);
 
-#[cfg(any(test, all(feature = "svm", feature = "async")))]
-use once_cell::sync::Lazy;
-
 #[cfg(any(test, feature = "tests"))]
 use std::sync::Mutex;
 
 #[cfg(any(test, feature = "tests"))]
 #[allow(unused)]
-static LOCK: Lazy<Mutex<()>> = Lazy::new(|| Mutex::new(()));
+static LOCK: once_cell::sync::Lazy<Mutex<()>> = once_cell::sync::Lazy::new(|| Mutex::new(()));
 
 /// take the lock in tests, we use this to enforce that
 /// a test does not run while a compiler version is being installed

ethers-solc/src/report.rs

@@ -5,6 +5,7 @@ use semver::Version;
 use std::{
     error::Error,
     fmt,
+    path::Path,
     sync::{
         atomic::{AtomicUsize, Ordering},
         Arc,
@@ -65,6 +66,9 @@ pub trait Reporter: 'static {
 
     /// Invoked before a new [`Solc`] bin was successfully installed
     fn on_solc_installation_success(&self, _version: &Version) {}
+
+    /// Invoked if the import couldn't be resolved
+    fn on_unresolved_import(&self, _import: &Path) {}
 }
 
 pub(crate) fn solc_spawn(solc: &Solc, version: &Version, input: &CompilerInput) {
@@ -85,6 +89,10 @@ pub(crate) fn solc_installation_success(version: &Version) {
     with_global(|r| r.reporter.on_solc_installation_success(version));
 }
 
+pub(crate) fn unresolved_import(import: &Path) {
+    with_global(|r| r.reporter.on_unresolved_import(import));
+}
+
 fn get_global() -> Option<&'static Report> {
     if GLOBAL_REPORTER_STATE.load(Ordering::SeqCst) != SET {
         return None
@@ -139,6 +147,10 @@ impl Reporter for BasicStdoutReporter {
     fn on_solc_installation_success(&self, version: &Version) {
         println!("Successfully installed solc {}", version);
     }
+
+    fn on_unresolved_import(&self, import: &Path) {
+        println!("Unable to resolve imported file: \"{}\"", import.display());
+    }
 }
 
 /// Returned if setting the global reporter fails.

ethers-solc/src/resolver.rs

@@ -239,7 +239,10 @@ impl Graph {
                     Ok(import) => {
                         add_node(&mut unresolved, &mut index, &mut resolved_imports, import)?;
                     }
-                    Err(err) => tracing::trace!("failed to resolve import component \"{:?}\"", err),
+                    Err(err) => {
+                        crate::report::unresolved_import(import.data());
+                        tracing::trace!("failed to resolve import component \"{:?}\"", err)
+                    }
                 };
             }
             nodes.push(node);