Parse exceptions during reloads

src/ghci/parse/ghc_message/exception.rs

@@ -0,0 +1,54 @@
+use winnow::PResult;
+use winnow::Parser;
+
+use crate::ghci::parse::lines::until_newline;
+
+use super::GhcMessage;
+
+/// Parse an "Exception" message like this:
+///
+/// ```plain
+/// *** Exception: /Users/.../dist-newstyle/ghc82733_tmp_1/ghc_tmp_34657.h: withFile: does not exist (No such file or directory)
+/// ```
+pub fn exception(input: &mut &str) -> PResult<GhcMessage> {
+    let _ = "*** Exception: ".parse_next(input)?;
+
+    let message = until_newline.parse_next(input)?;
+
+    Ok(GhcMessage::Exception(message.to_owned()))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use indoc::indoc;
+    use pretty_assertions::assert_eq;
+
+    #[test]
+    fn test_parse_exception() {
+        assert_eq!(
+            exception.parse("*** Exception: Uh oh!\n").unwrap(),
+            GhcMessage::Exception("Uh oh!".into())
+        );
+
+        assert_eq!(
+            exception.parse("*** Exception: /Users/.../dist-newstyle/ghc82733_tmp_1/ghc_tmp_34657.h: withFile: does not exist (No such file or directory)\n").unwrap(),
+            GhcMessage::Exception("/Users/.../dist-newstyle/ghc82733_tmp_1/ghc_tmp_34657.h: withFile: does not exist (No such file or directory)".into())
+        );
+
+        // Doesn't parse subsequent lines (even if they're relevant, unfortunately).
+        assert_eq!(
+            exception
+                .parse(indoc!(
+                    "
+                    *** Exception: puppy doggy
+                    CallStack (from HasCallStack):
+                      error, called at <interactive>:3:1 in interactive:Ghci1
+                    "
+                ))
+                .unwrap(),
+            GhcMessage::Exception("puppy doggy".into())
+        );
+    }
+}

src/ghci/parse/ghc_message/mod.rs

@@ -44,6 +44,9 @@ use module_import_cycle_diagnostic::module_import_cycle_diagnostic;
 mod no_location_info_diagnostic;
 use no_location_info_diagnostic::no_location_info_diagnostic;
 
+mod exception;
+use exception::exception;
+
 use super::rest_of_line;
 use super::CompilingModule;
 
@@ -64,6 +67,15 @@ pub enum GhcMessage {
     /// Foo.hs:81:1: Warning: Defined but not used: `bar'
     /// ```
     Diagnostic(GhcDiagnostic),
+    /// An exception while running a command or similar.
+    ///
+    /// These may be multiple lines, but there's no good way to determine where the message ends,
+    /// so we just parse the first line.
+    ///
+    /// ```text
+    /// *** Exception: /Users/.../dist-newstyle/ghc82733_tmp_1/ghc_tmp_34657.h: withFile: does not exist (No such file or directory)
+    /// ```
+    Exception(String),
     /// A configuration file being loaded.
     ///
     /// ```text
@@ -181,6 +193,7 @@ fn parse_messages_inner(input: &mut &str) -> PResult<Vec<GhcMessage>> {
                 .map(Item::One),
             module_import_cycle_diagnostic.map(Item::Many),
             loaded_configuration.map(Item::One),
+            exception.map(Item::One),
             rest_of_line.map(|line| {
                 tracing::debug!(line, "Ignoring GHC output line");
                 Item::Ignore
@@ -290,6 +303,7 @@ mod tests {
                   |
                 4 | example = "example"
                   |           ^^^^^^^^^
+                *** Exception: /Users/.../dist-newstyle/ghc82733_tmp_1/ghc_tmp_34657.h: withFile: does not exist (No such file or directory)
                 Failed, two modules loaded.
                 "#
             ))
@@ -322,6 +336,7 @@ mod tests {
                         ].join("\n"),
                     },
                 ),
+                GhcMessage::Exception("/Users/.../dist-newstyle/ghc82733_tmp_1/ghc_tmp_34657.h: withFile: does not exist (No such file or directory)".to_owned()),
                 GhcMessage::Summary(
                     CompilationSummary {
                         result: CompilationResult::Err,

tests/all_good.rs

@@ -43,3 +43,33 @@ async fn can_detect_compilation_failure() {
         .await
         .unwrap();
 }
+
+/// Test that `ghciwatch` can detect an `*** Exception` diagnostic.
+///
+/// Regression test for DUX-3144.
+#[test]
+async fn can_detect_exception() {
+    let mut session = GhciWatchBuilder::new("tests/data/simple")
+        .start()
+        .await
+        .expect("ghciwatch starts");
+    session.wait_until_ready().await.expect("ghciwatch loads");
+
+    let module_path = session.path("src/MyModule.hs");
+
+    session
+        .fs()
+        .prepend(&module_path, "{-# OPTIONS_GHC -F -pgmF false #-}\n")
+        .await
+        .unwrap();
+
+    session
+        .wait_for_log(BaseMatcher::compilation_failed())
+        .await
+        .unwrap();
+
+    session
+        .wait_for_log(BaseMatcher::reload_completes().but_not(BaseMatcher::message("All good!")))
+        .await
+        .unwrap();
+}

tests/data/simple/src/MyModule.hs

@@ -1,3 +1,5 @@
+{-# OPTIONS_GHC -F -pgmF false #-}
+
 module MyModule (example) where
 
 example :: String