Exception: 'run_command unexpected stderr' when running wasm2js tests with nodejs-14.5.0

[rathann]

$ ./check.py --binaryen-bin build/bin wasm2js
warning: no mozjs found (did not check native wasm support nor asm.js validation)
warning: no interpreter provided (did not test spec interpreter validation)

[ checking wasm2js testcases... ]

.. empty_table.wast
executing:  /builddir/build/BUILD/binaryen-version_95/build/bin/wasm2js split.wast -all --disable-exception-handling
executing:  /builddir/build/BUILD/binaryen-version_95/build/bin/wasm2js split.wast -all --disable-exception-handling --allow-asserts
executing:  /builddir/build/BUILD/binaryen-version_95/build/bin/wasm2js split.wast -all --disable-exception-handling --allow-asserts
[PassRunner] running passes...
[PassRunner]   running pass: autodrop...                          2.165e-06 seconds.
[PassRunner]   (validating)
[PassRunner]   running pass: legalize-js-interface...             1.0406e-05 seconds.
[PassRunner]   (validating)
[PassRunner]   running pass: remove-non-js-ops...                 8.381e-06 seconds.
[PassRunner]   (validating)
[PassRunner]   running pass: flatten...                           9.77e-07 seconds.
[PassRunner]   (validating)
[PassRunner]   running pass: i64-to-i32-lowering...               2.0394e-05 seconds.
[PassRunner]   (validating)
[PassRunner]   running pass: alignment-lowering...                3.562e-06 seconds.
[PassRunner]   (validating)
[PassRunner]   running pass: flatten...                           1.606e-06 seconds.
[PassRunner]   (validating)
[PassRunner]   running pass: simplify-locals-notee-nostructure... 1.536e-06 seconds.
[PassRunner]   (validating)
[PassRunner]   running pass: reorder-locals...                    1.676e-06 seconds.
[PassRunner]   (validating)
[PassRunner]   running pass: vacuum...                            1.327e-06 seconds.
[PassRunner]   (validating)
[PassRunner]   running pass: remove-unused-module-elements...     8.311e-06 seconds.
[PassRunner]   (validating)
[PassRunner]   running pass: dce...                               1.397e-06 seconds.
[PassRunner]   (validating)
[PassRunner] passes took 6.1738e-05 seconds.
[PassRunner] (final validation)
executing:  /usr/bin/node --experimental-modules --loader /builddir/build/BUILD/binaryen-version_95/scripts/test/node-esm-loader.mjs a.2asm.mjs
(node:187260) ExperimentalWarning: --experimental-loader is an experimental feature. This feature could change at any time
(Use `node --trace-warnings ...` to show where the warning was created)
executing:  /usr/bin/node --experimental-modules --loader /builddir/build/BUILD/binaryen-version_95/scripts/test/node-esm-loader.mjs a.2asm.asserts.mjs
Traceback (most recent call last):
  File "/builddir/build/BUILD/binaryen-version_95/./check.py", line 403, in <module>
    sys.exit(main())
  File "/builddir/build/BUILD/binaryen-version_95/./check.py", line 386, in main
    TEST_SUITES[test]()
  File "/builddir/build/BUILD/binaryen-version_95/scripts/test/wasm2js.py", line 124, in test_wasm2js
    test_wasm2js_output()
  File "/builddir/build/BUILD/binaryen-version_95/scripts/test/wasm2js.py", line 90, in test_wasm2js_output
    out = support.run_command(cmd, expected_err='', err_ignore='ExperimentalWarning')
  File "/builddir/build/BUILD/binaryen-version_95/scripts/test/support.py", line 182, in run_command
    raise Exception(('run_command unexpected stderr',
Exception: ('run_command unexpected stderr', "expected '', actual '(Use `node --trace-warnings ...` to show where the warning was created)\n'")

This is with nodejs-14.5.0.

Indeed, running the above command directly gives an extra line of output:

$ cd out/test/
$ /usr/bin/node --experimental-modules --loader /builddir/build/BUILD/binaryen-version_95/scripts/test/node-esm-loader.mjs a.2asm.mjs
(node:187299) ExperimentalWarning: --experimental-loader is an experimental feature. This feature could change at any time
(Use `node --trace-warnings ...` to show where the warning was created)

[rathann]

For now, I'm using the patch below as a work-around:

diff -up binaryen-version_95/scripts/test/wasm2js.py.node binaryen-version_95/scripts/test/wasm2js.py
--- binaryen-version_95/scripts/test/wasm2js.py.node    2020-07-21 06:04:33.000000000 +0200
+++ binaryen-version_95/scripts/test/wasm2js.py 2020-07-21 13:43:50.093293525 +0200
@@ -80,7 +80,7 @@ def test_wasm2js_output():
                 # `spectest` and `env` modules in our tests.
                 if shared.NODEJS:
                     loader = os.path.join(shared.options.binaryen_root, 'scripts', 'test', 'node-esm-loader.mjs')
-                    node = [shared.NODEJS, '--experimental-modules', '--loader', loader]
+                    node = [shared.NODEJS, '--experimental-modules', '--no-warnings', '--loader', loader]
                     cmd = node[:]
                     cmd.append('a.2asm.mjs')
                     out = support.run_command(cmd)

[kripken]

@rathann Interesting, looks like a new node warning then. I think that diff looks good - please open a PR with that, thanks!

[kripken]

Fixed by that PR.