Display first pretty type error

1 files changed, 24 insertions, 1 deletions

diff --git a/dhall/src/tests.rs b/dhall/src/tests.rs
index 9790b95..cde3b03 100644
--- a/dhall/src/tests.rs
+++ b/dhall/src/tests.rs
@@ -20,6 +20,29 @@ right: `{}`"#,
     }};
 }
 
+/// Wrapper around string slice that makes debug output `{:?}` to print string same way as `{}`.
+/// Used in different `assert*!` macros in combination with `pretty_assertions` crate to make
+/// test failures to show nice diffs.
+#[derive(PartialEq, Eq)]
+#[doc(hidden)]
+pub struct PrettyString(String);
+
+/// Make diff to display string as multi-line string
+impl std::fmt::Debug for PrettyString {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        f.write_str(&self.0)
+    }
+}
+
+macro_rules! assert_eq_pretty_str {
+    ($left:expr, $right:expr) => {
+        assert_eq_pretty!(
+            PrettyString($left.to_string()),
+            PrettyString($right.to_string())
+        );
+    };
+}
+
 use std::fs::File;
 use std::io::{Read, Write};
 use std::path::PathBuf;
@@ -172,7 +195,7 @@ pub fn run_test(test: Test<'_>) -> Result<()> {
             if error_file_path.is_file() {
                 let expected_msg = std::fs::read_to_string(error_file_path)?;
                 let msg = format!("{}\n", err);
-                assert_eq_pretty!(msg, expected_msg);
+                assert_eq_pretty_str!(msg, expected_msg);
             } else {
                 std::fs::create_dir_all(error_file_path.parent().unwrap())?;
                 let mut file = File::create(error_file_path)?;