Add error message when file is not found

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project does not currently adhere to a particular versioning scheme.
 
 - Add import system. ([#544][gh-544])
 - Add multi line comment `#{ ... #}` syntax. ([#595][gh-595])
+- Add error message when input file is not found. ([#513][gh-513])
 
 ## [0.2.36] - 2024-07-04
 
@@ -372,6 +373,7 @@ and this project does not currently adhere to a particular versioning scheme.
 [gh-494]: https://github.com/HigherOrderCO/Bend/issues/494
 [gh-502]: https://github.com/HigherOrderCO/Bend/issues/502
 [gh-512]: https://github.com/HigherOrderCO/Bend/issues/512
+[gh-513]: https://github.com/HigherOrderCO/Bend/issues/513
 [gh-514]: https://github.com/HigherOrderCO/Bend/issues/514
 [gh-516]: https://github.com/HigherOrderCO/Bend/issues/516
 [gh-526]: https://github.com/HigherOrderCO/Bend/issues/526

src/fun/load_book.rs

@@ -16,8 +16,16 @@ pub fn load_file_to_book(
   package_loader: impl PackageLoader,
   diag: DiagnosticsConfig,
 ) -> Result<Book, Diagnostics> {
-  let code = std::fs::read_to_string(path).map_err(|e| e.to_string())?;
-  load_to_book(path, &code, package_loader, diag)
+  match path.try_exists() {
+    Ok(exists) => {
+      if !exists {
+        return Err(format!("The file '{}' was not found.", path.display()).into());
+      }
+      let code = std::fs::read_to_string(path).map_err(|e| e.to_string())?;
+      load_to_book(path, &code, package_loader, diag)
+    }
+    Err(e) => Err(e.to_string().into()),
+  }
 }
 
 pub fn load_to_book(