Export package version [core] (#131)

* Exports the current package version from the root level. This allows
users of this module to read the version of the library that has been
loaded.

* The `opencensus-exporter-ocagent` has been updated to support the newly
exported version.

Author: justindsmith

packages/opencensus-core/src/common/version.ts

@@ -0,0 +1,28 @@
+
+/**
+ * Copyright 2018, OpenCensus 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.
+ */
+
+type Package = {
+  version: string;
+};
+
+// Load the package details. Note that the `require` is performed at runtime,
+// which means the source files will be in the `/build` directory, so the
+// package path is relative to that location.
+const pjson: Package = require('../../../package.json');
+
+// Export the core package version
+export const version: string = pjson.version;

packages/opencensus-core/src/index.ts

@@ -55,3 +55,6 @@ export * from './stats/types';
 // logger
 import * as logger from './common/console-logger';
 export {logger};
+
+// version
+export * from './common/version';

packages/opencensus-exporter-ocagent/src/ocagent.ts

@@ -15,7 +15,7 @@
  */
 
 import * as protoLoader from '@grpc/proto-loader';
-import {Exporter, ExporterBuffer, ExporterConfig, logger, Logger, RootSpan, SamplerBuilder} from '@opencensus/core';
+import {Exporter, ExporterBuffer, ExporterConfig, logger, Logger, RootSpan, SamplerBuilder, version as coreVersion} from '@opencensus/core';
 import * as tracing from '@opencensus/nodejs';
 import * as grpc from 'grpc';
 import * as os from 'os';
@@ -91,8 +91,7 @@ export class OCAgentExporter implements Exporter {
      * Get node properties
      */
     this.exporterVersion = require('../../package.json').version;
-    this.coreVersion =
-        require('../../node_modules/@opencensus/core/package.json').version;
+    this.coreVersion = coreVersion;
     this.hostName = os.hostname();
     this.processStartTimeMillis = Date.now() - (process.uptime() * 1000);