feat(solc): improve error on case mismatch (#1998)

ethers-solc/src/error.rs

@@ -27,18 +27,19 @@ pub enum SolcError {
     /// Filesystem IO error
     #[error(transparent)]
     Io(#[from] SolcIoError),
+    #[error("File could not be resolved due to broken symlink: {0}.")]
+    ResolveBadSymlink(SolcIoError),
     /// Failed to resolve a file
     #[error("Failed to resolve file: {0}.\n Check configured remappings.")]
     Resolve(SolcIoError),
-    #[error("File could not be resolved due to broken symlink: {0}.")]
-    ResolveBadSymlink(SolcIoError),
+    #[error("File cannot be resolved due to mismatch of file name case: {error}.\n Found existing file: {existing_file:?}\n Please check the case of the import.")]
+    ResolveCaseSensitiveFileName { error: SolcIoError, existing_file: PathBuf },
     #[error(
-        r#"Failed to resolve file: {0}.
+        r#"{0}.
     --> {1:?}
-        {2:?}
-    Check configured remappings."#
+        {2:?}"#
     )]
-    FailedResolveImport(SolcIoError, PathBuf, PathBuf),
+    FailedResolveImport(Box<SolcError>, PathBuf, PathBuf),
     #[cfg(feature = "svm-solc")]
     #[error(transparent)]
     SvmError(#[from] svm::SolcVmError),

ethers-solc/src/resolver/mod.rs

@@ -59,6 +59,7 @@ use std::{
 mod parse;
 mod tree;
 
+use crate::utils::find_case_sensitive_existing_file;
 pub use parse::SolImportAlias;
 pub use tree::{print, Charset, TreeOptions};
 
@@ -371,10 +372,12 @@ impl Graph {
                         add_node(&mut unresolved, &mut index, &mut resolved_imports, import)
                             .map_err(|err| {
                                 match err {
-                                    SolcError::Resolve(err) => {
-                                        // make the error more verbose
+                                    err @ SolcError::ResolveCaseSensitiveFileName { .. } |
+                                    err @ SolcError::Resolve(_) => {
+                                        // make the error more helpful by providing additional
+                                        // context
                                         SolcError::FailedResolveImport(
-                                            err,
+                                            Box::new(err),
                                             node.path.clone(),
                                             import_path.clone(),
                                         )
@@ -832,10 +835,21 @@ impl Node {
     pub fn read(file: impl AsRef<Path>) -> Result<Self> {
         let file = file.as_ref();
         let source = Source::read(file).map_err(|err| {
-            if !err.path().exists() && err.path().is_symlink() {
+            let exists = err.path().exists();
+            if !exists && err.path().is_symlink() {
                 SolcError::ResolveBadSymlink(err)
             } else {
-                SolcError::Resolve(err)
+                // This is an additional check useful on OS that have case-sensitive paths, See also <https://docs.soliditylang.org/en/v0.8.17/path-resolution.html#import-callback>
+                if !exists {
+                    // check if there exists a file with different case
+                    if let Some(existing_file) = find_case_sensitive_existing_file(file) {
+                        SolcError::ResolveCaseSensitiveFileName { error: err, existing_file }
+                    } else {
+                        SolcError::Resolve(err)
+                    }
+                } else {
+                    SolcError::Resolve(err)
+                }
             }
         })?;
         let data = SolData::parse(source.as_ref(), file);

ethers-solc/src/utils.rs

@@ -385,6 +385,26 @@ pub(crate) fn find_fave_or_alt_path(root: impl AsRef<Path>, fave: &str, alt: &st
     p
 }
 
+/// Attempts to find a file with different case that exists next to the `non_existing` file
+pub(crate) fn find_case_sensitive_existing_file(non_existing: &Path) -> Option<PathBuf> {
+    let non_existing_file_name = non_existing.file_name()?;
+    let parent = non_existing.parent()?;
+    WalkDir::new(parent)
+        .max_depth(1)
+        .into_iter()
+        .filter_map(Result::ok)
+        .filter(|e| e.file_type().is_file())
+        .find_map(|e| {
+            let existing_file_name = e.path().file_name()?;
+            if existing_file_name.eq_ignore_ascii_case(non_existing_file_name) &&
+                existing_file_name != non_existing_file_name
+            {
+                return Some(e.path().to_path_buf())
+            }
+            None
+        })
+}
+
 #[cfg(not(target_arch = "wasm32"))]
 use tokio::runtime::{Handle, Runtime};
 
@@ -453,6 +473,7 @@ pub fn create_parent_dir_all(file: impl AsRef<Path>) -> Result<(), SolcError> {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use crate::resolver::Node;
     use solang_parser::pt::SourceUnitPart;
     use std::{
         collections::HashSet,
@@ -460,6 +481,45 @@ mod tests {
     };
     use tempdir;
 
+    #[test]
+    fn can_find_different_case() {
+        let tmp_dir = tempdir("out").unwrap();
+        let path = tmp_dir.path().join("forge-std");
+        create_dir_all(&path).unwrap();
+        let existing = path.join("Test.sol");
+        let non_existing = path.join("test.sol");
+        std::fs::write(&existing, b"").unwrap();
+
+        #[cfg(target_os = "linux")]
+        assert!(!non_existing.exists());
+
+        let found = find_case_sensitive_existing_file(&non_existing).unwrap();
+        assert_eq!(found, existing);
+    }
+
+    #[cfg(target_os = "linux")]
+    #[test]
+    fn can_read_different_case() {
+        let tmp_dir = tempdir("out").unwrap();
+        let path = tmp_dir.path().join("forge-std");
+        create_dir_all(&path).unwrap();
+        let existing = path.join("Test.sol");
+        let non_existing = path.join("test.sol");
+        std::fs::write(
+            &existing,
+            r#"
+pragma solidity ^0.8.10;
+contract A {}
+        "#,
+        )
+        .unwrap();
+
+        assert!(!non_existing.exists());
+
+        let found = Node::read(&non_existing).unwrap_err();
+        matches!(found, SolcError::ResolveCaseSensitiveFileName { .. });
+    }
+
     #[test]
     fn can_create_parent_dirs_with_ext() {
         let tmp_dir = tempdir("out").unwrap();