Add get writer project id

src/trace-api.js

@@ -25,6 +25,7 @@ var SpanData = require('./span-data.js');
 var uuid = require('uuid');
 var TracingPolicy = require('./tracing-policy.js');
 var semver = require('semver');
+var TraceWriter = require('./trace-writer.js');
 
 var ROOT_SPAN_STACK_OFFSET = semver.satisfies(process.version, '>=8') ? 0 : 2;
 
@@ -36,9 +37,10 @@ var ROOT_SPAN_STACK_OFFSET = semver.satisfies(process.version, '>=8') ? 0 : 2;
 var phantomApiImpl = {
   enhancedDatabaseReportingEnabled: function() { return false; },
   runInRootSpan: function(opts, fn) { return fn(null); },
-  getCurrentContext: function() { return null; },
+  getCurrentContextId: function() { return null; },
   createChildSpan: function(opts) { return null; },
   getResponseTraceContext: function(context, traced) { return ''; },
+  getWriterProjectId : function() { return null; },
   wrap: function(fn) { return fn; },
   wrapEmitter: function(ee) {},
 };
@@ -196,6 +198,23 @@ TraceAgent.prototype.getCurrentContextId = function() {
   return rootSpan.trace.traceId;
 };
 
+/**
+ * Returns the projectId that was either configured or auto-discovered by the
+ * TraceWriter. Note that the auto-discovery is done asynchronously, so this
+ * will return null until the projectId auto-discovery completes.
+ */
+TraceAgent.prototype.getWriterProjectId = function() {
+  var traceWriter;
+  try {
+     traceWriter = TraceWriter.get();
+  } catch(err) {
+    // The TraceWriter.get() call could fail if the TraceWriter has not been
+    // initialized yet.
+    return null;
+  }
+  return traceWriter.config().projectId;
+};
+
 /**
  * Creates and returns a new ChildSpan object nested within the root span. If
  * there is no current RootSpan object, this function returns null.

test/test-trace-api.js

@@ -49,6 +49,7 @@ function assertAPISurface(traceAPI) {
     }
   });
   assert.strictEqual(typeof traceAPI.getCurrentContextId, 'function');
+  assert.strictEqual(typeof traceAPI.getWriterProjectId, 'function');
   var child = traceAPI.createChildSpan({ name: 'child' });
   // TODO: Ditto but with child spans
   if (child) {
@@ -180,7 +181,12 @@ describe('Trace Interface', function() {
       traceAPI.runInRootSpan({name: 'root', url: 'root'}, function(rootSpan) {
         var id = traceAPI.getCurrentContextId();
         assert.strictEqual(id, rootSpan.trace.traceId);
-      });      
+      });
+    });
+
+    it('should return get the project ID if set in the writer', function() {
+      var traceApi = createTraceAgent();
+      assert.equal(traceApi.getWriterProjectId(), '0');
     });
 
     it('should add labels to spans', function() {