Make detection of prompt types more robust

crates/ark/src/interface.rs

@@ -597,6 +597,13 @@ impl RMain {
         buflen: c_int,
         _hist: c_int,
     ) -> ConsoleResult {
+        // TODO!: Document why incomplete is fine (vec is necessarily empty, if
+        // there's a syntax error R will throw and vec will be flushed)
+
+        // TODO!: If we detect an incomplete prompt and we no longer have any
+        // inputs to send, then it's a panic. We should have replied with an
+        // error to the frontend ahead of time.
+
         if let Some(console_result) = self.handle_pending_line(buf, buflen) {
             return console_result;
         }
@@ -849,7 +856,7 @@ impl RMain {
         self.error_occurred = false;
 
         match input {
-            ConsoleInput::Input(mut code) => {
+            ConsoleInput::Input(code) => {
                 // Handle commands for the debug interpreter
                 if self.dap.is_debugging() {
                     let continue_cmds = vec!["n", "f", "c", "cont"];
@@ -858,13 +865,7 @@ impl RMain {
                     }
                 }
 
-                // In notebooks, wrap in braces so that only the last complete
-                // expression is auto-printed
-                if let SessionMode::Notebook = self.session_mode {
-                    code = format!("{{ {code} }}");
-                }
-
-                // WIP: Split input into multiple lines
+                // TODO!: Check for incomplete inputs and immediately error
                 let code = self.handle_input(code);
 
                 Self::on_console_input(buf, buflen, code);
@@ -1348,33 +1349,46 @@ This is a Positron limitation we plan to fix. In the meantime, you can:
             }
         }
 
-        // If we are at top-level, we're handling visible output auto-printed by
-        // the R REPL. We accumulate this output (it typically comes in multiple
-        // parts) so we can emit it later on as part of the execution reply
-        // message sent to Shell, as opposed to an Stdout message sent on IOPub.
-        //
-        // However, if autoprint is dealing with an intermediate expression
-        // (i.e. `a` and `b` in `a\nb\nc`), we should emit it on IOPub. We
-        // only accumulate autoprint output for the very last expression. The
-        // way to distinguish between these cases is whether there are still
-        // lines of input pending. In that case, that means we are on an
-        // intermediate expression.
-        //
-        // Note that we implement this behaviour (streaming autoprint results of
-        // intermediate expressions) specifically for Positron, and specifically
-        // for versions that send multiple expressions selected by the user in
-        // one request. Other Jupyter frontends do not want to see output for
-        // these intermediate expressions. And future versions of Positron will
-        // never send multiple expressions in one request
-        // (https://github.com/posit-dev/positron/issues/1326).
-        //
-        // Note that warnings emitted lazily on stdout will appear to be part of
-        // autoprint. We currently emit them on stderr, which allows us to
-        // differentiate, but that could change in the future:
-        // https://github.com/posit-dev/positron/issues/1881
-        if otype == 0 && is_auto_printing() && self.pending_lines.is_empty() {
-            self.autoprint_output.push_str(&content);
-            return;
+        if stream == Stream::Stdout && is_auto_printing() {
+            // If we are at top-level, we're handling visible output auto-printed by
+            // the R REPL. We accumulate this output (it typically comes in multiple
+            // parts) so we can emit it later on as part of the execution reply
+            // message sent to Shell, as opposed to an Stdout message sent on IOPub.
+            //
+            // However, if autoprint is dealing with an intermediate expression
+            // (i.e. `a` and `b` in `a\nb\nc`), we should emit it on IOPub. We
+            // only accumulate autoprint output for the very last expression. The
+            // way to distinguish between these cases is whether there are still
+            // lines of input pending. In that case, that means we are on an
+            // intermediate expression.
+            //
+            // Note that we implement this behaviour (streaming autoprint results of
+            // intermediate expressions) specifically for Positron, and specifically
+            // for versions that send multiple expressions selected by the user in
+            // one request. Other Jupyter frontends do not want to see output for
+            // these intermediate expressions. And future versions of Positron will
+            // never send multiple expressions in one request
+            // (https://github.com/posit-dev/positron/issues/1326).
+            //
+            // Note that warnings emitted lazily on stdout will appear to be part of
+            // autoprint. We currently emit them on stderr, which allows us to
+            // differentiate, but that could change in the future:
+            // https://github.com/posit-dev/positron/issues/1881
+
+            // Handle last expression
+            if self.pending_lines.is_empty() {
+                self.autoprint_output.push_str(&content);
+                return;
+            }
+
+            // In notebooks, we don't emit results of intermediate expressions
+            if self.session_mode == SessionMode::Notebook {
+                return;
+            }
+
+            // In Positron, fall through if we have pending input. This allows
+            // autoprint output for intermediate expressions to be emitted on
+            // IOPub.
         }
 
         // Stream output via the IOPub channel.