Add Links and Events to OStreamSpanExporter (#663)

* Add Links and Events to OStreamSpanExporter

Previously these were just ignored. Summary of changes:

- Moved print methods into the translation unit
- Added new print methods for links and events
- Refactored tests
  - Added new convenience OStream capture utility
  - Restructured tests to focus on stream tests and feature tests
- Added new tests for links and events

* Add new test utility to bazel build

exporters/ostream/BUILD

@@ -60,10 +60,21 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "ostream_capture",
+    hdrs = [
+        "test/ostream_capture.h",
+    ],
+    deps = [
+        "//api",
+    ],
+)
+
 cc_test(
     name = "ostream_span_test",
     srcs = ["test/ostream_span_test.cc"],
     deps = [
+        ":ostream_capture",
         ":ostream_span_exporter",
         "@com_google_googletest//:gtest_main",
     ],

exporters/ostream/include/opentelemetry/exporters/ostream/span_exporter.h

@@ -95,7 +95,7 @@ class OStreamSpanExporter final : public sdktrace::SpanExporter
 
 #endif
 
-  void print_value(sdkcommon::OwnedAttributeValue &value)
+  void print_value(const sdkcommon::OwnedAttributeValue &value)
   {
 #if __cplusplus < 201402L
     nostd::visit(OwnedAttributeValueVisitor(*this), value);
@@ -104,17 +104,13 @@ class OStreamSpanExporter final : public sdktrace::SpanExporter
 #endif
   }
 
-  void printAttributes(std::unordered_map<std::string, sdkcommon::OwnedAttributeValue> map)
-  {
-    size_t size = map.size();
-    // size_t i    = 1;
-    for (auto kv : map)
-    {
-      sout_ << "\t" << kv.first << ": ";
-      print_value(kv.second);
-      sout_ << std::endl;
-    }
-  }
+  // various print helpers
+  void printAttributes(const std::unordered_map<std::string, sdkcommon::OwnedAttributeValue> &map,
+                       const std::string prefix = "\n\t");
+
+  void printEvents(const std::vector<sdktrace::SpanDataEvent> &events);
+
+  void printLinks(const std::vector<sdktrace::SpanDataLink> &links);
 };
 }  // namespace trace
 }  // namespace exporter

exporters/ostream/src/span_exporter.cc

@@ -69,10 +69,14 @@ sdktrace::ExportResult OStreamSpanExporter::Export(
             << "\n  duration      : " << span->GetDuration().count()
             << "\n  description   : " << span->GetDescription()
             << "\n  span kind     : " << span->GetSpanKind()
-            << "\n  status        : " << statusMap[int(span->GetStatus())] << "\n  attributes    : "
-            << "\n";
+            << "\n  status        : " << statusMap[int(span->GetStatus())]
+            << "\n  attributes    : ";
       printAttributes(span->GetAttributes());
-      sout_ << "}\n";
+      sout_ << "\n  events        : ";
+      printEvents(span->GetEvents());
+      sout_ << "\n  links         : ";
+      printLinks(span->GetLinks());
+      sout_ << "\n}\n";
     }
   }
 
@@ -85,6 +89,48 @@ bool OStreamSpanExporter::Shutdown(std::chrono::microseconds timeout) noexcept
   return true;
 }
 
+void OStreamSpanExporter::printAttributes(
+    const std::unordered_map<std::string, sdkcommon::OwnedAttributeValue> &map,
+    const std::string prefix)
+{
+  for (const auto &kv : map)
+  {
+    sout_ << prefix << kv.first << ": ";
+    print_value(kv.second);
+  }
+}
+
+void OStreamSpanExporter::printEvents(const std::vector<sdktrace::SpanDataEvent> &events)
+{
+  for (const auto &event : events)
+  {
+    sout_ << "\n\t{"
+          << "\n\t  name          : " << event.GetName()
+          << "\n\t  timestamp     : " << event.GetTimestamp().time_since_epoch().count()
+          << "\n\t  attributes    : ";
+    printAttributes(event.GetAttributes(), "\n\t\t");
+    sout_ << "\n\t}";
+  }
+}
+
+void OStreamSpanExporter::printLinks(const std::vector<sdktrace::SpanDataLink> &links)
+{
+  for (const auto &link : links)
+  {
+    char trace_id[32] = {0};
+    char span_id[16]  = {0};
+    link.GetSpanContext().trace_id().ToLowerBase16(trace_id);
+    link.GetSpanContext().span_id().ToLowerBase16(span_id);
+    sout_ << "\n\t{"
+          << "\n\t  trace_id      : " << std::string(trace_id, 32)
+          << "\n\t  span_id       : " << std::string(span_id, 16)
+          << "\n\t  tracestate    : " << link.GetSpanContext().trace_state()->ToHeader()
+          << "\n\t  attributes    : ";
+    printAttributes(link.GetAttributes(), "\n\t\t");
+    sout_ << "\n\t}";
+  }
+}
+
 }  // namespace trace
 }  // namespace exporter
 OPENTELEMETRY_END_NAMESPACE

exporters/ostream/test/ostream_capture.h

@@ -0,0 +1,57 @@
+#pragma once
+
+#include <iostream>
+#include <sstream>
+#include <string>
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace exporter
+{
+namespace ostream
+{
+namespace test
+{
+/**
+ * The OStreamCapture captures from the specified stream for its lifetime
+ */
+class OStreamCapture
+{
+public:
+  /**
+   * Create a OStreamCapture which will capture the output of the ostream that it was constructed
+   * with for the lifetime of the instance.
+   */
+  OStreamCapture(std::ostream &ostream) : stream_(ostream), buf_(ostream.rdbuf())
+  {
+    stream_.rdbuf(captured_.rdbuf());
+  }
+
+  ~OStreamCapture() { stream_.rdbuf(buf_); }
+
+  /**
+   * Returns the captured data from the stream.
+   */
+  std::string GetCaptured() const { return captured_.str(); }
+
+private:
+  std::ostream &stream_;
+  std::streambuf *buf_;
+  std::stringstream captured_;
+};
+
+/**
+ * Helper method to invoke the passed func while recording the output of the specified stream and
+ * return the output afterwards.
+ */
+template <typename Func>
+std::string WithOStreamCapture(std::ostream &stream, Func func)
+{
+  OStreamCapture capture(stream);
+  func();
+  return capture.GetCaptured();
+}
+
+}  // namespace test
+}  // namespace ostream
+}  // namespace exporter
+OPENTELEMETRY_END_NAMESPACE