write server list to stdout

instead of logging, which goes to stderr and is often prefixed and/or filtered by log levels

jupyter_server/serverapp.py

@@ -677,20 +677,19 @@ class JupyterServerListApp(JupyterApp):
 
     def start(self):
         """Start the server list application."""
-        info = self.log.info
         serverinfo_list = list(list_running_servers(self.runtime_dir, log=self.log))
         if self.jsonlist:
-            info(json.dumps(serverinfo_list, indent=2))
+            print(json.dumps(serverinfo_list, indent=2))
         elif self.json:
             for serverinfo in serverinfo_list:
-                info(json.dumps(serverinfo))
+                print(json.dumps(serverinfo))
         else:
-            info("Currently running servers:")
+            print("Currently running servers:")
             for serverinfo in serverinfo_list:
                 url = serverinfo["url"]
                 if serverinfo.get("token"):
                     url = url + "?token=%s" % serverinfo["token"]
-                info("%s :: %s", url, serverinfo["root_dir"])
+                print(url, "::", serverinfo["root_dir"])
 
 
 # -----------------------------------------------------------------------------

pyproject.toml

@@ -246,6 +246,8 @@ unfixable = [
 # S108 Probable insecure usage of temporary file or directory
 # PLC1901 `ext_pkg.version == ""` can be simplified to `not ext_pkg.version` as an empty string is falsey
 "tests/*" = ["B011", "F841", "C408", "E402", "T201", "EM101", "EM102", "EM103", "PLR2004", "S108", "PLC1901"]
+# print should be used in applications
+"**/*app.py" = ["T201"]
 # Ignore flake 8 errors from shimmed imports
 "jupyter_server/base/zmqhandlers.py" = ["F401"]
 # PLR2004 Magic value used in comparison

tests/test_serverapp.py

@@ -1,7 +1,9 @@
 import getpass
+import json
 import logging
 import os
 import pathlib
+import sys
 import warnings
 from unittest.mock import patch
 
@@ -14,6 +16,7 @@
 from jupyter_server.auth.security import passwd_check
 from jupyter_server.serverapp import (
     JupyterPasswordApp,
+    JupyterServerListApp,
     ServerApp,
     ServerWebApplication,
     list_running_servers,
@@ -36,6 +39,49 @@ def test_help_output():
     check_help_all_output("jupyter_server")
 
 
+@pytest.mark.parametrize(
+    "format",
+    [
+        "json",
+        "jsonlist",
+        "",
+    ],
+)
+def test_server_list(jp_configurable_serverapp, capsys, format):
+    app = jp_configurable_serverapp(log=logging.getLogger())
+
+    app.write_server_info_file()
+
+    capsys.readouterr()
+    listapp = JupyterServerListApp(
+        parent=app,
+    )
+    if format:
+        setattr(listapp, format, True)
+    listapp.start()
+    captured = capsys.readouterr()
+    sys.stdout.write(captured.out)
+    sys.stderr.write(captured.err)
+    out = captured.out.strip()
+
+    if not format:
+        assert "Currently running servers:" in out
+        assert app.connection_url in out
+        assert len(out.splitlines()) == 2
+        return
+
+    if format == "jsonlist":
+        servers = json.loads(out)
+    elif format == "json":
+        servers = [json.loads(line) for line in out.splitlines()]
+    assert len(servers) == 1
+    sinfo = servers[0]
+
+    assert sinfo["port"] == app.port
+    assert sinfo["url"] == app.connection_url
+    assert sinfo["version"] == app.version
+
+
 def test_server_info_file(tmp_path, jp_configurable_serverapp):
     app = jp_configurable_serverapp(log=logging.getLogger())