From c7f267569a90ee8cf73620e944f7f9356c7ed516 Mon Sep 17 00:00:00 2001
From: JasonXZLiu <liujasn@amazon.com>
Date: Wed, 16 Sep 2020 20:41:24 -0700
Subject: [PATCH] Override setattr and delattr for SpanContext + add tests

---
 .../src/opentelemetry/trace/span.py           | 53 ++++++++++++----
 .../tests/trace/test_immutablespancontext.py  | 62 +++++++++++++++++++
 2 files changed, 104 insertions(+), 11 deletions(-)
 create mode 100644 opentelemetry-api/tests/trace/test_immutablespancontext.py

diff --git a/opentelemetry-api/src/opentelemetry/trace/span.py b/opentelemetry-api/src/opentelemetry/trace/span.py
index 27bbc223368..b9724028836 100644
--- a/opentelemetry-api/src/opentelemetry/trace/span.py
+++ b/opentelemetry-api/src/opentelemetry/trace/span.py
@@ -143,7 +143,7 @@ def get_default(cls) -> "TraceState":
 DEFAULT_TRACE_STATE = TraceState.get_default()
 
 
-class SpanContext:
+class SpanContext(tuple):
     """The state of a Span to propagate between processes.
 
     This class includes the immutable attributes of a :class:`.Span` that must
@@ -157,8 +157,8 @@ class SpanContext:
         is_remote: True if propagated from a remote parent.
     """
 
-    def __init__(
-        self,
+    def __new__(
+        cls,
         trace_id: int,
         span_id: int,
         is_remote: bool,
@@ -169,16 +169,47 @@ def __init__(
             trace_flags = DEFAULT_TRACE_OPTIONS
         if trace_state is None:
             trace_state = DEFAULT_TRACE_STATE
-        self.trace_id = trace_id
-        self.span_id = span_id
-        self.trace_flags = trace_flags
-        self.trace_state = trace_state
-        self.is_remote = is_remote
-        self.is_valid = (
-            self.trace_id != INVALID_TRACE_ID
-            and self.span_id != INVALID_SPAN_ID
+            
+        is_valid = (
+            trace_id != INVALID_TRACE_ID
+            and span_id != INVALID_SPAN_ID
         )
 
+        return tuple.__new__(cls, (trace_id, span_id, trace_flags, trace_state, is_remote, is_valid))
+
+    @property
+    def trace_id(self):
+        return tuple.__getitem__(self, 0)
+
+    @property
+    def span_id(self):
+        return tuple.__getitem__(self, 1)
+
+    @property
+    def trace_flags(self):
+        return tuple.__getitem__(self, 2)
+
+    @property
+    def trace_state(self):
+        return tuple.__getitem__(self, 3)
+
+    @property
+    def is_remote(self):
+        return tuple.__getitem__(self, 4)
+
+    @property
+    def is_valid(self):
+        return tuple.__getitem__(self, 5)
+
+    def __getattr__(self, *args):
+        raise TypeError
+
+    def __setattr__(self, *args):
+        raise TypeError
+
+    def __delattr__(self, *args):
+        raise TypeError
+
     def __repr__(self) -> str:
         return (
             "{}(trace_id={}, span_id={}, trace_state={!r}, is_remote={})"
diff --git a/opentelemetry-api/tests/trace/test_immutablespancontext.py b/opentelemetry-api/tests/trace/test_immutablespancontext.py
new file mode 100644
index 00000000000..cc99a359e6e
--- /dev/null
+++ b/opentelemetry-api/tests/trace/test_immutablespancontext.py
@@ -0,0 +1,62 @@
+# Copyright The OpenTelemetry Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import unittest
+
+from opentelemetry import trace
+
+
+class TestImmutableSpanContext(unittest.TestCase):
+    def test_ctor(self):
+        context = trace.SpanContext(
+            1,
+            1,
+            is_remote=False,
+            trace_flags=trace.DEFAULT_TRACE_OPTIONS,
+            trace_state=trace.DEFAULT_TRACE_STATE,
+        )
+
+        self.assertEqual(context.trace_id, 1)
+        self.assertEqual(context.span_id, 1)
+        self.assertEqual(context.is_remote, False)
+        self.assertEqual(context.trace_flags, trace.DEFAULT_TRACE_OPTIONS)
+        self.assertEqual(context.trace_state, trace.DEFAULT_TRACE_STATE)
+
+    def test_attempt_change_attributes(self):
+        context = trace.SpanContext(
+            1,
+            1,
+            is_remote=False,
+            trace_flags=trace.DEFAULT_TRACE_OPTIONS,
+            trace_state=trace.DEFAULT_TRACE_STATE,
+        )
+
+        with self.assertRaises(TypeError):
+            context.trace_id = 2
+        with self.assertRaises(TypeError):
+            context.span_id = 2
+        with self.assertRaises(TypeError):
+            context.is_remote = True
+        with self.assertRaises(TypeError):
+            context.trace_flags = 2
+        with self.assertRaises(TypeError):
+            context.trace_state = 2
+
+        self.assertEqual(context.trace_id, 1)
+        self.assertEqual(context.span_id, 1)
+        self.assertEqual(context.is_remote, False)
+        self.assertEqual(context.trace_flags, trace.DEFAULT_TRACE_OPTIONS)
+        self.assertEqual(context.trace_state, trace.DEFAULT_TRACE_STATE)
+
+        self.assertEqual(context.trace_id, 1)