perf jevents: Move json encoding to its own functions

Have dedicated encode functions rather than having them embedded in
MetricGroup. This is to provide some uniformity in the Metric ToXXX
routines.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Thomas Falcon <thomas.falcon@intel.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

tools/perf/pmu-events/metric.py

@@ -484,15 +484,6 @@ class Metric:
   def ToMetricGroupDescriptions(self, root: bool = True) -> Dict[str, str]:
     return {}
 
-class _MetricJsonEncoder(json.JSONEncoder):
-  """Special handling for Metric objects."""
-
-  def default(self, o):
-    if isinstance(o, Metric):
-      return o.ToPerfJson()
-    return json.JSONEncoder.default(self, o)
-
-
 class MetricGroup:
   """A group of metrics.
 
@@ -523,8 +514,11 @@ class MetricGroup:
 
     return result
 
-  def ToPerfJson(self) -> str:
-    return json.dumps(sorted(self.Flatten()), indent=2, cls=_MetricJsonEncoder)
+  def ToPerfJson(self) -> List[Dict[str, str]]:
+    result = []
+    for x in sorted(self.Flatten()):
+      result.append(x.ToPerfJson())
+    return result
 
   def ToMetricGroupDescriptions(self, root: bool = True) -> Dict[str, str]:
     result = {self.name: self.description} if self.description else {}
@@ -533,7 +527,23 @@ class MetricGroup:
     return result
 
   def __str__(self) -> str:
-    return self.ToPerfJson()
+    return str(self.ToPerfJson())
+
+
+def JsonEncodeMetric(x: MetricGroup):
+  class MetricJsonEncoder(json.JSONEncoder):
+    """Special handling for Metric objects."""
+
+    def default(self, o):
+      if isinstance(o, Metric) or isinstance(o, MetricGroup):
+        return o.ToPerfJson()
+      return json.JSONEncoder.default(self, o)
+
+  return json.dumps(x, indent=2, cls=MetricJsonEncoder)
+
+
+def JsonEncodeMetricGroupDescriptions(x: MetricGroup):
+  return json.dumps(x.ToMetricGroupDescriptions(), indent=2)
 
 
 class _RewriteIfExpToSelect(ast.NodeTransformer):