Add BuilltIn.Reset Log Level. Fixes #4930.

atest/robot/standard_libraries/builtin/set_log_level.robot

@@ -26,6 +26,15 @@ Set Log Level
 Invalid Log Level Failure Is Catchable
     Check Test Case    ${TESTNAME}
 
+Reset Log Level
+    ${tc} =    Check Test Case    ${TESTNAME}
+    Check Log Message    ${tc.kws[0].msgs[0]}    Log level changed from INFO to DEBUG.    DEBUG
+    Check Log Message    ${tc.kws[1].msgs[0]}    This is logged    INFO
+    Check Log Message    ${tc.kws[2].msgs[0]}    This is logged    DEBUG
+    Should Be Empty      ${tc.kws[3].msgs}
+    Check Log Message    ${tc.kws[4].msgs[0]}    This is logged    INFO
+    Should Be Empty      ${tc.kws[5].msgs}
+
 Log Level Goes To HTML
     File Should Contain    ${OUTDIR}${/}set_log_level_log.html    KW Info to log
     File Should Contain    ${OUTDIR}${/}set_log_level_log.html    KW Trace to log

atest/testdata/standard_libraries/builtin/set_log_level.robot

@@ -27,7 +27,16 @@ Set Log Level
     [Teardown]    Set Log Level    INFO
 
 Invalid Log Level Failure Is Catchable
-    Run Keyword And Expect Error    Invalid log level 'INVALID'.    Set Log Level    INVALID
+    [Documentation]    FAIL    Invalid log level 'INVALID'.
+    Set Log Level    INVALID
+
+Reset Log Level
+    Set Log Level    DEBUG
+    Log    This is logged    INFO
+    Log    This is logged    DEBUG
+    Reset Log Level
+    Log    This is logged        INFO
+    Log    This is not logged    DEBUG
 
 Log Level Goes To HTML
     Set Log Level    Trace

src/robot/libraries/BuiltIn.py

@@ -3160,19 +3160,34 @@ def comment(self, *messages):
         pass
 
     def set_log_level(self, level):
-        """Sets the log threshold to the specified level and returns the old level.
+        """Sets the log threshold to the specified level.
 
         Messages below the level will not logged. The default logging level is
-        INFO, but it can be overridden with the command line option ``--loglevel``.
-
-        The available levels: TRACE, DEBUG, INFO (default), WARN, ERROR and NONE
+        INFO, but it can be overridden with the ``--loglevel`` command line option.
+        The available levels are TRACE, DEBUG, INFO (default), WARN, ERROR and NONE
         (no logging).
+
+        The old level is returned and can be used for setting the level back
+        later. An alternative way to reset the level is using the dedicated
+        `Reset Log Level` keyword.
         """
         old = self._context.output.set_log_level(level)
         self._namespace.variables.set_global('${LOG_LEVEL}', level.upper())
         self.log(f'Log level changed from {old} to {level.upper()}.', level='DEBUG')
         return old
 
+    def reset_log_level(self):
+        """Resets the log level to the original value.
+
+        The original log level is set from the command line with the ``--loglevel``
+        option and is INFO by default. The active log level can be changed using
+        the `Set Log Level` keyword.
+
+        New in Robot Framework 7.0.
+        """
+        level = self._context.output.initial_log_level
+        return self.set_log_level(level)
+
     def reload_library(self, name_or_instance):
         """Rechecks what keywords the specified library provides.
 

src/robot/output/output.py

@@ -34,6 +34,10 @@ def __init__(self, settings):
         self._register_loggers(DebugFile(settings.debug_file))
         self._settings = settings
 
+    @property
+    def initial_log_level(self):
+        return self._settings.log_level
+
     def _register_loggers(self, debug_file):
         LOGGER.register_xml_logger(self._xml_logger)
         LOGGER.register_listeners(self.listeners or None, self.library_listeners)