fix(tools): don't force PIXLET_EDITOR_HOST, and stop hard-assuming the MQTT bridge is uninstalled in tests

CodeRabbit review on #544:
- start_pixlet_editor() unconditionally set PIXLET_EDITOR_HOST=0.0.0.0,
  overriding any operator-configured loopback-only value and always exposing
  the unauthenticated `pixlet serve` dev process on the LAN (CWE-1188). Use
  env.setdefault() so it's only a default; also stop hardcoding 'host' in the
  recorded session state so status reporting matches what was actually used.
- test_tools_sections.js asserted an Install button always renders, which
  assumes the bridge service is never installed on the test/dev host. Branch
  on the same service.installed flag the template itself renders from.

Adds regression coverage in test_starlark_pixlet_routes.py for the
setdefault-vs-override behavior (both the "nothing configured" and
"operator pinned loopback" cases).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S3bPMESe2TfrGvbs1ef9c5

test/js/dom/test_tools_sections.js

@@ -63,7 +63,16 @@ const get = p => new Promise((res, rej) =>
      !/s3cret|mqtt_password"\s*:\s*"/.test(window.document.body.innerHTML));
   ok('state badge rendered', ($('mqtt-bridge-state').textContent || '').trim().length > 0,
      $('mqtt-bridge-state').textContent);
-  ok('not-installed shows an Install button', !!$('btn-mqtt-install'));
+  // The dev/test machine may or may not actually have the bridge service
+  // installed -- branch on the same `service.installed` flag the template
+  // itself renders from, rather than hard-assuming "not installed" (which
+  // fails on any host where the service happens to be present).
+  if (bridge.data.service.installed) {
+    ok('installed shows Restart/Start-Stop buttons, not Install',
+       !$('btn-mqtt-install') && !!$('btn-mqtt-restart') && !!$('btn-mqtt-startstop'));
+  } else {
+    ok('not-installed shows an Install button', !!$('btn-mqtt-install'));
+  }
   ok('config path shown', $('mqtt-bridge-body').textContent.includes('bridge_config.json'));
   ok('env override hint shown', $('mqtt-bridge-body').textContent.includes('LEDMATRIX_MQTT_'));
 

test/web_interface/test_starlark_pixlet_routes.py

@@ -748,3 +748,66 @@ class TestTheStoreUsesTheTokenTheUserConfigured:
             client.get('/api/v3/starlark/repository/browse')
 
         repo.assert_called_once_with(github_token='ghp_configured')
+
+
+class TestPixletEditorHostDefaultsButDoesNotOverride:
+    """PIXLET_EDITOR_HOST must default to 0.0.0.0, never force it.
+
+    A browser reaching the editor is remote by definition, so a session with
+    nothing configured has to bind more than loopback to be reachable at
+    all -- but an operator who has deliberately pinned PIXLET_EDITOR_HOST to
+    loopback (e.g. in the systemd unit's Environment=, to edit only over an
+    SSH tunnel) must keep that setting. The previous unconditional
+    ``env['PIXLET_EDITOR_HOST'] = '0.0.0.0'`` overrode it every time,
+    always exposing the unauthenticated ``pixlet serve`` dev process on the
+    LAN regardless (CodeQL CWE-1188).
+    """
+
+    @pytest.fixture
+    def app_dir(self, tmp_path):
+        d = tmp_path / "demo_app"
+        d.mkdir()
+        (d / "demo_app.star").write_text("def main():\n    pass\n")
+        return d
+
+    def _start(self, client, app_dir, tmp_path, operator_host):
+        from web_interface.blueprints import api_v3 as mod
+
+        script = tmp_path / "pixlet_config_editor.sh"
+        script.write_text("#!/bin/bash\n")
+        state_file = tmp_path / "pixlet_editor_state.json"
+        captured = {}
+
+        class FakeProcess:
+            pid = 424242
+
+        def fake_popen(cmd, cwd=None, env=None, stdout=None, stderr=None,
+                       start_new_session=None):
+            captured['env'] = env
+            return FakeProcess()
+
+        with patch.object(mod, '_validate_starlark_app_path',
+                          return_value=(app_dir, None)), \
+             patch.object(mod, '_PIXLET_EDITOR_SCRIPT', script), \
+             patch.object(mod, '_PIXLET_EDITOR_STATE', state_file), \
+             patch.object(mod, '_find_pixlet_binary', return_value='/usr/bin/pixlet'), \
+             patch.object(mod.subprocess, 'Popen', side_effect=fake_popen), \
+             patch.dict(os.environ):
+            if operator_host is None:
+                os.environ.pop('PIXLET_EDITOR_HOST', None)
+            else:
+                os.environ['PIXLET_EDITOR_HOST'] = operator_host
+            resp = client.post('/api/v3/starlark/editor/start',
+                                json={'app_id': app_dir.name})
+
+        assert resp.status_code == 200, resp.get_json()
+        assert 'env' in captured, "subprocess.Popen was never called"
+        return captured['env']
+
+    def test_defaults_to_0_0_0_0_when_operator_set_nothing(self, client, app_dir, tmp_path):
+        env = self._start(client, app_dir, tmp_path, operator_host=None)
+        assert env['PIXLET_EDITOR_HOST'] == '0.0.0.0'
+
+    def test_keeps_an_operator_configured_loopback_host(self, client, app_dir, tmp_path):
+        env = self._start(client, app_dir, tmp_path, operator_host='127.0.0.1')
+        assert env['PIXLET_EDITOR_HOST'] == '127.0.0.1'

web_interface/blueprints/api_v3.py

@@ -10087,8 +10087,11 @@ def start_pixlet_editor():
         env['PIXLET_EDITOR_PORT'] = str(port)
         env['PIXLET_EDITOR_TIMEOUT'] = str(timeout_s)
         # A browser reaching this endpoint is remote by definition, so the
-        # session has to listen on more than loopback to be usable at all.
-        env['PIXLET_EDITOR_HOST'] = '0.0.0.0'
+        # session needs to listen on more than loopback to be usable at all --
+        # but only as a *default*. An operator who has already set
+        # PIXLET_EDITOR_HOST (e.g. to keep it loopback-only even from the web
+        # UI) must not have that overridden here.
+        env.setdefault('PIXLET_EDITOR_HOST', '0.0.0.0')
 
         log_path = Path(tempfile.gettempdir()) / 'ledmatrix_pixlet_editor.log'
         log_handle = open(log_path, 'w', encoding='utf-8')  # noqa: SIM115 - owned by the child
@@ -10107,7 +10110,7 @@ def start_pixlet_editor():
         now = time.time()
         state = {'pid': process.pid, 'app_id': app_dir.name, 'port': port,
                  'timeout': timeout_s, 'started_at': now, 'deadline': now + timeout_s,
-                 'host': '0.0.0.0', 'log': str(log_path)}
+                 'host': env['PIXLET_EDITOR_HOST'], 'log': str(log_path)}
         try:
             with open(_PIXLET_EDITOR_STATE, 'w', encoding='utf-8') as handle:
                 json.dump(state, handle)