perf(deps): avoid semver where possible (#1309)

avoid loading the semver dependency.

src/cls.ts

@@ -13,7 +13,6 @@
 // limitations under the License.
 
 import {EventEmitter} from 'events';
-import * as semver from 'semver';
 
 import {AsyncHooksCLS} from './cls/async-hooks';
 import {AsyncListenerCLS} from './cls/async-listener';
@@ -27,8 +26,6 @@ import {UNCORRELATED_ROOT_SPAN, DISABLED_ROOT_SPAN} from './span-data';
 import {Trace, TraceSpan} from './trace';
 import {Singleton} from './util';
 
-const asyncHooksAvailable = semver.satisfies(process.version, '>=8');
-
 export interface RealRootContext {
   readonly span: TraceSpan;
   readonly trace: Trace;
@@ -115,11 +112,6 @@ export class TraceCLS implements CLS<RootContext> {
   constructor(config: TraceCLSConfig, private readonly logger: Logger) {
     switch (config.mechanism) {
       case TraceCLSMechanism.ASYNC_HOOKS:
-        if (!asyncHooksAvailable) {
-          throw new Error(
-            `CLS mechanism [${config.mechanism}] is not compatible with Node <8.`
-          );
-        }
         this.CLSClass = AsyncHooksCLS;
         this.rootSpanStackOffset = 4;
         break;

src/index.ts

@@ -16,7 +16,6 @@ const filesLoadedBeforeTrace = Object.keys(require.cache);
 
 // This file's top-level imports must not transitively depend on modules that
 // do I/O, or continuation-local-storage will not work.
-import * as semver from 'semver';
 import {Config, defaultConfig} from './config';
 import * as extend from 'extend';
 import * as path from 'path';
@@ -28,6 +27,16 @@ import {TraceCLSMechanism} from './cls';
 import {StackdriverTracer} from './trace-api';
 import {TraceContextHeaderBehavior} from './tracing-policy';
 
+if (process && process.version) {
+  const minNodeVersion = 10;
+  const major = Number(process.version.match(/v(\d+)/)![1]);
+  if (major < minNodeVersion) {
+    throw Error(
+      `trace-agent supports a minimum Node.js version of ${minNodeVersion}. Read our version support policy: https://github.com/googleapis/cloud-trace-nodejs#supported-nodejs-versions`
+    );
+  }
+}
+
 export {Config, PluginTypes};
 
 let traceAgent: StackdriverTracer;
@@ -88,11 +97,8 @@ function initConfig(userConfig: Forceable<Config>): TopLevelConfig {
   const getInternalClsMechanism = (clsMechanism: string): TraceCLSMechanism => {
     // If the CLS mechanism is set to auto-determined, decide now
     // what it should be.
-    const ahAvailable = semver.satisfies(process.version, '>=8');
     if (clsMechanism === 'auto') {
-      return ahAvailable
-        ? TraceCLSMechanism.ASYNC_HOOKS
-        : TraceCLSMechanism.ASYNC_LISTENER;
+      return TraceCLSMechanism.ASYNC_HOOKS;
     }
     return clsMechanism as TraceCLSMechanism;
   };

src/plugins/plugin-http.ts

@@ -15,7 +15,6 @@
 import * as httpModule from 'http';
 import {Agent, ClientRequest, ClientRequestArgs, request} from 'http';
 import * as httpsModule from 'https';
-import * as semver from 'semver';
 import * as shimmer from 'shimmer';
 import {URL, UrlWithStringQuery} from 'url';
 
@@ -31,12 +30,7 @@ const ERR_HTTP_HEADERS_SENT_MSG = "Can't set headers after they are sent.";
 // URL is used for type checking, but doesn't exist in Node <7.
 // This function works around that.
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
-const isURL = semver.satisfies(process.version, '>=7')
-  ? // eslint-disable-next-line @typescript-eslint/no-explicit-any
-    (value: any): value is URL => value instanceof URL
-  : // eslint-disable-next-line
-    (value: any): value is URL => false;
-// tslint:enable:no-any
+const isURL = (value: any): value is URL => value instanceof URL;
 
 function getSpanName(options: ClientRequestArgs | URL) {
   // c.f. _http_client.js ClientRequest constructor
@@ -268,28 +262,26 @@ function patchHttp(http: HttpModule, api: Tracer) {
     return makeRequestTrace('http:', request, api);
   });
 
-  if (semver.satisfies(process.version, '>=8.0.0')) {
-    // http.get in Node 8 calls the private copy of request rather than the one
-    // we have patched on module.export, so patch get as well.
-    shimmer.wrap(http, 'get', (): typeof http.get => {
-      // Re-implement http.get. This needs to be done (instead of using
-      // makeRequestTrace to patch it) because we need to set the trace
-      // context header before the returned ClientRequest is ended.
-      // The Node.js docs state that the only differences between request and
-      // get are that (1) get defaults to the HTTP GET method and (2) the
-      // returned request object is ended immediately.
-      // The former is already true (at least in supported Node versions up to
-      // v9), so we simply follow the latter.
-      // Ref:
-      // https://nodejs.org/dist/latest/docs/api/http.html#http_http_get_options_callback
-      return function getTrace(this: never) {
-        // eslint-disable-next-line prefer-rest-params
-        const req = http.request.apply(this, arguments);
-        req.end();
-        return req;
-      };
-    });
-  }
+  // http.get in Node 8 calls the private copy of request rather than the one
+  // we have patched on module.export, so patch get as well.
+  shimmer.wrap(http, 'get', (): typeof http.get => {
+    // Re-implement http.get. This needs to be done (instead of using
+    // makeRequestTrace to patch it) because we need to set the trace
+    // context header before the returned ClientRequest is ended.
+    // The Node.js docs state that the only differences between request and
+    // get are that (1) get defaults to the HTTP GET method and (2) the
+    // returned request object is ended immediately.
+    // The former is already true (at least in supported Node versions up to
+    // v9), so we simply follow the latter.
+    // Ref:
+    // https://nodejs.org/dist/latest/docs/api/http.html#http_http_get_options_callback
+    return function getTrace(this: never) {
+      // eslint-disable-next-line prefer-rest-params
+      const req = http.request.apply(this, arguments);
+      req.end();
+      return req;
+    };
+  });
 }
 
 // https.get depends on Node http internals in 8.9.0 and 9+ instead of the
@@ -310,9 +302,7 @@ function patchHttps(https: HttpsModule, api: Tracer) {
 
 function unpatchHttp(http: HttpModule) {
   shimmer.unwrap(http, 'request');
-  if (semver.satisfies(process.version, '>=8.0.0')) {
-    shimmer.unwrap(http, 'get');
-  }
+  shimmer.unwrap(http, 'get');
 }
 
 function unpatchHttps(https: HttpsModule) {