fix(terminal): avoid merging heredoc EOF with fence wrapper (#3598)

One-shot local execution built `printf FENCE; <cmd>; __hermes_rc=...`, so a
command ending in a heredoc produced a closing line like `EOF; __hermes_rc=...`,
which is not a valid delimiter. Bash then treated the rest of the wrapper as
heredoc body, leaking it into tool output (e.g. gh issue/PR flows).

Use newline-separated wrapper lines so the delimiter stays alone and the
trailer runs after the heredoc completes.

Co-authored-by: kshitijk4poor <82637225+kshitijk4poor@users.noreply.github.com>

tests/tools/test_local_persistent.py

@@ -63,6 +63,18 @@ class TestLocalOneShotRegression:
         assert r["output"].strip() == ""
         env.cleanup()
 
+    def test_oneshot_heredoc_does_not_leak_fence_wrapper(self):
+        """Heredoc closing line must not be merged with the fence wrapper tail."""
+        env = LocalEnvironment(persistent=False)
+        cmd = "cat <<'H_EOF'\nheredoc body line\nH_EOF"
+        r = env.execute(cmd)
+        env.cleanup()
+        assert r["returncode"] == 0
+        assert "heredoc body line" in r["output"]
+        assert "__hermes_rc" not in r["output"]
+        assert "printf '" not in r["output"]
+        assert "exit $" not in r["output"]
+
 
 class TestLocalPersistent:
     @pytest.fixture

tools/environments/local.py

@@ -391,12 +391,17 @@ class LocalEnvironment(PersistentShellMixin, BaseEnvironment):
             effective_stdin = stdin_data
 
         user_shell = _find_bash()
+        # Newline-separated wrapper (not `cmd; __hermes_rc=...` on one line).
+        # A trailing `; __hermes_rc` glued to `<<EOF` / a closing `EOF` line breaks
+        # heredoc parsing: the delimiter must be alone on its line, otherwise the
+        # rest of this script becomes heredoc body and leaks into stdout (e.g. gh
+        # issue/PR flows that use here-documents for bodies).
         fenced_cmd = (
-            f"printf '{_OUTPUT_FENCE}';"
-            f" {exec_command};"
-            f" __hermes_rc=$?;"
-            f" printf '{_OUTPUT_FENCE}';"
-            f" exit $__hermes_rc"
+            f"printf '{_OUTPUT_FENCE}'\n"
+            f"{exec_command}\n"
+            f"__hermes_rc=$?\n"
+            f"printf '{_OUTPUT_FENCE}'\n"
+            f"exit $__hermes_rc\n"
         )
         run_env = _make_run_env(self.env)