add support for 0 global attribute limit and tests (open-telemetry#2398)

* add support for 0 global attribute limit and tests

* add PR number to changelog

Author: Arnatious

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased](https://github.com/open-telemetry/opentelemetry-python/compare/v1.8.0-0.27b0...HEAD)
 
+- Fix SpanLimits global span limit defaulting when set to 0
+  ([#2398](https://github.com/open-telemetry/opentelemetry-python/pull/2398))
 - Decode URL-encoded headers in environment variables
   ([#2312](https://github.com/open-telemetry/opentelemetry-python/pull/2312))
 - [exporter/opentelemetry-exporter-otlp-proto-grpc] Add OTLPMetricExporter

opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py

@@ -594,23 +594,31 @@ def __init__(
             max_attributes, OTEL_ATTRIBUTE_COUNT_LIMIT
         )
         self.max_attributes = (
-            global_max_attributes or _DEFAULT_OTEL_ATTRIBUTE_COUNT_LIMIT
+            global_max_attributes
+            if global_max_attributes is not None
+            else _DEFAULT_OTEL_ATTRIBUTE_COUNT_LIMIT
         )
 
         self.max_span_attributes = self._from_env_if_absent(
             max_span_attributes,
             OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT,
-            global_max_attributes or _DEFAULT_OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT,
+            global_max_attributes
+            if global_max_attributes is not None
+            else _DEFAULT_OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT,
         )
         self.max_event_attributes = self._from_env_if_absent(
             max_event_attributes,
             OTEL_EVENT_ATTRIBUTE_COUNT_LIMIT,
-            global_max_attributes or _DEFAULT_OTEL_EVENT_ATTRIBUTE_COUNT_LIMIT,
+            global_max_attributes
+            if global_max_attributes is not None
+            else _DEFAULT_OTEL_EVENT_ATTRIBUTE_COUNT_LIMIT,
         )
         self.max_link_attributes = self._from_env_if_absent(
             max_link_attributes,
             OTEL_LINK_ATTRIBUTE_COUNT_LIMIT,
-            global_max_attributes or _DEFAULT_OTEL_LINK_ATTRIBUTE_COUNT_LIMIT,
+            global_max_attributes
+            if global_max_attributes is not None
+            else _DEFAULT_OTEL_LINK_ATTRIBUTE_COUNT_LIMIT,
         )
 
         # attribute length

opentelemetry-sdk/tests/trace/test_trace.py

@@ -1594,6 +1594,53 @@ def test_span_no_limits_code(self):
             )
         )
 
+    def test_span_zero_global_limit(self):
+        self._test_span_limits(
+            new_tracer(
+                span_limits=trace.SpanLimits(
+                    max_attributes=0,
+                    max_events=0,
+                    max_links=0,
+                )
+            ),
+            0,
+            0,
+            0,
+            0,
+            0,
+        )
+
+    def test_span_zero_global_nonzero_model(self):
+        self._test_span_limits(
+            new_tracer(
+                span_limits=trace.SpanLimits(
+                    max_attributes=0,
+                    max_events=0,
+                    max_links=0,
+                    max_span_attributes=15,
+                    max_span_attribute_length=25,
+                )
+            ),
+            15,
+            0,
+            0,
+            0,
+            25,
+        )
+
+    def test_span_zero_global_unset_model(self):
+        self._test_span_no_limits(
+            new_tracer(
+                span_limits=trace.SpanLimits(
+                    max_attributes=0,
+                    max_span_attributes=trace.SpanLimits.UNSET,
+                    max_links=trace.SpanLimits.UNSET,
+                    max_events=trace.SpanLimits.UNSET,
+                    max_attribute_length=trace.SpanLimits.UNSET,
+                )
+            )
+        )
+
     def test_dropped_attributes(self):
         span = get_span_with_dropped_attributes_events_links()
         self.assertEqual(1, span.dropped_links)