[LIT] Add JSONMetricValue type to wrap types supported by the json encoder.

Summary:
The following types can be encoded and decoded by the json library:
`dict`, `list`, `tuple`, `str`, `unicode`, `int`, `long`, `float`, `bool`, `NoneType`. 

`JSONMetricValue` can be constructed with any of these types, and used as part of Test.Result.
This patch also adds a toMetricValue function that converts a value into a MetricValue.




Reviewers: ddunbar, EricWF

Reviewed By: EricWF

Subscribers: cfe-commits, llvm-commits

Differential Revision: http://reviews.llvm.org/D6576

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224628 91177308-0d34-0410-b5e6-96231b3b80d8

utils/lit/lit/Test.py

@@ -1,5 +1,6 @@
 import os
 from xml.sax.saxutils import escape
+from json import JSONEncoder
 
 # Test result codes.
 
@@ -73,6 +74,41 @@ class RealMetricValue(MetricValue):
     def todata(self):
         return self.value
 
+class JSONMetricValue(MetricValue):
+    """
+        JSONMetricValue is used for types that are representable in the output
+        but that are otherwise uninterpreted.
+    """
+    def __init__(self, value):
+        # Ensure the value is a serializable by trying to encode it.
+        # WARNING: The value may change before it is encoded again, and may
+        #          not be encodable after the change.
+        try:
+            e = JSONEncoder()
+            e.encode(value)
+        except TypeError:
+            raise
+        self.value = value
+
+    def format(self):
+        return str(self.value)
+
+    def todata(self):
+        return self.value
+
+def toMetricValue(value):
+    if isinstance(value, MetricValue):
+        return value
+    elif isinstance(value, int) or isinstance(value, long):
+        return IntMetricValue(value)
+    elif isinstance(value, float):
+        return RealMetricValue(value)
+    else:
+        # Try to create a JSONMetricValue and let the constructor throw
+        # if value is not a valid type.
+        return JSONMetricValue(value)
+
+
 # Test results.
 
 class Result(object):