suppresses extraneous stdout

cpp/examples/ExampleFunctions/CMakeLists.txt

@@ -10,3 +10,4 @@ add_test(ExampleFunctions call_with_optional_string)
 add_test(ExampleFunctions pass_by_reference_dict)
 add_test(ExampleFunctions pass_by_reference_vector)
 add_test(ExampleFunctions throws_error)
+add_test(ExampleFunctions returns_noisy_int)

cpp/examples/ExampleFunctions/returns_noisy_int.cpp

@@ -0,0 +1,20 @@
+// Copyright 2020 Lawrence Livermore National Security, LLC and other CLIPPy
+// Project Developers. See the top-level COPYRIGHT file for details.
+//
+// SPDX-License-Identifier: MIT
+
+#include <clippy/clippy.hpp>
+
+int main(int argc, char **argv) {
+  clippy::clippy clip("returns_noisy_int",
+                      "Tests returning a int with some extraneous stdout");
+  clip.returns<size_t>("The Int");
+  if (clip.parse(argc, argv)) {
+    return 0;
+  }
+
+  std::cout << "Here's some noise\n";
+  std::cout << "More noise!\n";
+  clip.to_return(size_t(42));
+  return 0;
+}

py/src/clippy/backends/fs/execution.py

@@ -10,6 +10,7 @@
 import os
 import select
 import subprocess
+import sys
 
 from ... import cfg
 from ...clippy_types import AnyDict
@@ -99,7 +100,12 @@ def _stream_exec(
                         stdout_buffer += text
                         while "\n" in stdout_buffer:
                             line, stdout_buffer = stdout_buffer.split("\n", 1)
-                            d = json.loads(line, object_hook=decode_clippy_json)
+                            try:
+                                d = json.loads(line, object_hook=decode_clippy_json)
+                            except json.JSONDecodeError:
+                                warning = f"Warning: invalid JSON on stdout: {line!r}"
+                                stderr_lines.append(warning + "\n")
+                                print(warning, file=sys.stderr, flush=True)
                     elif fd == stderr_fd:
                         stderr_buffer += text
                         while "\n" in stderr_buffer:

test/test_clippy.py

@@ -12,6 +12,9 @@
 clippy.logger.setLevel(logging.WARN)
 logging.getLogger().setLevel(logging.WARN)
 
+@pytest.fixture()
+def examplefn():
+    return clippy.ExampleFunctions()
 
 @pytest.fixture()
 def examplebag():
@@ -206,3 +209,9 @@ def test_graph(examplegraph):
     examplegraph.degree(examplegraph.node.degree)
     c_e_only = examplegraph.dump2(examplegraph.node.degree, where=examplegraph.node.degree > 2)
     assert "c" in c_e_only and "e" in c_e_only and len(c_e_only) == 2
+
+
+def test_noise(examplefn, capsys):
+    assert examplefn.returns_noisy_int() == 42
+    captured = capsys.readouterr()
+    assert "Warning: invalid JSON on stdout" in captured.err