BUG: Fix regression with run_subprocess (#11230)

mne/utils/misc.py

@@ -138,21 +138,22 @@ def run_subprocess(command, return_code=False, verbose=None, *args, **kwargs):
                 except Empty:
                     break
                 else:
+                    out = out.decode('utf-8')
                     # Strip newline at end of the string, otherwise we'll end
                     # up with two subsequent newlines (as the logger adds one)
                     #
                     # XXX Once we drop support for Python <3.9, uncomment the
                     # following line and remove the if/else block below.
                     #
-                    # out = out.decode('utf-8').removesuffix('\n')
-                    out = out.decode('utf-8')
+                    # log_out = out.removesuffix('\n')
                     if sys.version_info[:2] >= (3, 9):
-                        out = out.removesuffix('\n')
+                        log_out = out.removesuffix('\n')
+                    elif out.endswith('\n'):
+                        log_out = out[:-1]
                     else:
-                        if out.endswith('\n'):
-                            out = out[:-1]
+                        log_out = out
 
-                    logger.info(out)
+                    logger.info(log_out)
                     all_out += out
 
             while True:  # process stderr
@@ -161,27 +162,28 @@ def run_subprocess(command, return_code=False, verbose=None, *args, **kwargs):
                 except Empty:
                     break
                 else:
+                    err = err.decode('utf-8')
                     # Strip newline at end of the string, otherwise we'll end
                     # up with two subsequent newlines (as the logger adds one)
                     #
                     # XXX Once we drop support for Python <3.9, uncomment the
                     # following line and remove the if/else block below.
                     #
-                    # err = err.decode('utf-8').removesuffix('\n')
-                    err = err.decode('utf-8')
+                    # err_out = err.removesuffix('\n')
                     if sys.version_info[:2] >= (3, 9):
-                        err = err.removesuffix('\n')
+                        err_out = err.removesuffix('\n')
+                    elif err.endswith('\n'):
+                        err_out = err[:-1]
                     else:
-                        if err.endswith('\n'):
-                            err = err[:-1]
+                        err_out = err
 
                     # Leave this as logger.warning rather than warn(...) to
                     # mirror the logger.info above for stdout. This function
                     # is basically just a version of subprocess.call, and
                     # shouldn't emit Python warnings due to stderr outputs
                     # (the calling function can check for stderr output and
                     # emit a warning if it wants).
-                    logger.warning(err)
+                    logger.warning(err_out)
                     all_err += err
 
             if do_break:

mne/utils/tests/test_misc.py

@@ -1,7 +1,10 @@
 import os
+import sys
+
+import pytest
 
 import mne
-from mne.utils import sizeof_fmt
+from mne.utils import sizeof_fmt, run_subprocess, catch_logging
 
 
 def test_sizeof_fmt():
@@ -29,3 +32,33 @@ def test_html_repr():
     del os.environ[key]
     if existing_value is not None:
         os.environ[key, existing_value]
+
+
+@pytest.mark.parametrize('kind', ('stdout', 'stderr'))
+def test_run_subprocess(tmp_path, kind):
+    """Test run_subprocess."""
+    fname = tmp_path / 'subp.py'
+    with open(fname, 'w') as fid:
+        fid.write(f"""\
+import sys
+print('foo', file=sys.{kind})
+print('bar', file=sys.{kind})
+""")
+    with catch_logging() as log:
+        stdout, stderr = run_subprocess(
+            [sys.executable, str(fname)], verbose=True)
+    log = log.getvalue()
+    log = '\n'.join(log.split('\n')[1:])  # get rid of header
+    log = log.replace('\r\n', '\n')  # Windows
+    stdout = stdout.replace('\r\n', '\n')
+    stderr = stderr.replace('\r\n', '\n')
+    want = 'foo\nbar\n'
+    assert log == want
+    if kind == 'stdout':
+        std = stdout
+        other = stderr
+    else:
+        std = stderr
+        other = stdout
+    assert std == want
+    assert other == ''