Save/restore ConanOutput global state when using Conan API's command

conan/api/subapi/command.py

@@ -1,4 +1,5 @@
 from conans.errors import ConanException
+from conan.api.output import ConanOutput
 
 
 class CommandAPI:
@@ -20,5 +21,18 @@ def run(self, cmd):
             command = commands[current_cmd]
         except KeyError:
             raise ConanException(f"Command {current_cmd} does not exist")
+        # Conan has some global state in the ConanOutput class that
+        # get redefined when running a command and leak to the calling scope
+        # if running from a custom command.
+        # Store the old one and restore it after the command execution as a workaround.
+        _conan_output_level = ConanOutput._conan_output_level
+        _silent_warn_tags = ConanOutput._silent_warn_tags
+        _warnings_as_errors = ConanOutput._warnings_as_errors
 
-        return command.run_cli(self.conan_api, args)
+        try:
+            result = command.run_cli(self.conan_api, args)
+        finally:
+            ConanOutput._conan_output_level = _conan_output_level
+            ConanOutput._silent_warn_tags = _silent_warn_tags
+            ConanOutput._warnings_as_errors = _warnings_as_errors
+        return result

test/integration/command_v2/custom_commands_test.py

@@ -345,6 +345,32 @@ def mycmd2(conan_api, parser, *args, **kwargs):
         assert "MYCMD1!!!!!" in c.out
         assert "MYCMD2!!!!!" in c.out
 
+    def test_command_verbosity_leak(self):
+        mycommand = textwrap.dedent(f"""
+                    import json
+                    from conan.cli.command import conan_command
+                    from conan.api.output import ConanOutput
+
+                    @conan_command(group="custom commands")
+                    def mycommand(conan_api, parser, *args, **kwargs):
+                        \""" mycommand help \"""
+                        parser.add_argument("foo", help="foo")
+                        args = parser.parse_args(*args)
+
+                        out = ConanOutput()
+                        out.title("This is my first title")
+                        conan_api.command.run("config home")
+                        out.title("This is my second title")
+                    """)
+
+        c = TestClient()
+        command_file_path = os.path.join(c.cache_folder, 'extensions',
+                                         'commands', 'cmd_mycommand.py')
+        c.save({f"{command_file_path}": mycommand})
+        c.run("mycommand foo -vquiet")
+        assert "This is my first title" not in c.out
+        assert "This is my second title" not in c.out
+
     def test_command_reuse_interface_create(self):
         mycommand = textwrap.dedent("""
             import json