build: configure static globals to control bundle/debug code (#4273)

Author: mitsuhiko

packages/browser/rollup.config.js

@@ -9,6 +9,14 @@ const commitHash = require('child_process')
   .trim();
 
 const terserInstance = terser({
+  compress: {
+    // Tell env.ts that we're building a browser bundle and that we do not
+    // want to have unnecessary debug functionality.
+    global_defs: {
+      __SENTRY_BROWSER_BUNDLE__: true,
+      __SENTRY_NO_DEBUG__: true,
+    },
+  },
   mangle: {
     // captureExceptions and captureMessage are public API methods and they don't need to be listed here
     // as mangler doesn't touch user-facing thing, however sentryWrapped is not, and it would be mangled into a minified version.

packages/utils/src/env.ts

@@ -0,0 +1,31 @@
+/**
+ * This module mostly exists for optimizations in the build process
+ * through rollup and terser.  We define some global constants which
+ * are normally undefined.  However terser overrides these with global
+ * definitions which can be evaluated by the static analyzer when
+ * creating a bundle.
+ *
+ * In turn the `isDebugBuild` and `isBrowserBundle` functions are pure
+ * and can help us remove unused code from the bundles.
+ */
+
+declare const __SENTRY_BROWSER_BUNDLE__: boolean | undefined;
+declare const __SENTRY_NO_DEBUG__: boolean | undefined;
+
+/**
+ * Figures out if we're building with debug functionality.
+ *
+ * @returns true if this is a debug build
+ */
+export function isDebugBuild(): boolean {
+  return typeof __SENTRY_NO_DEBUG__ !== 'undefined' && !__SENTRY_BROWSER_BUNDLE__;
+}
+
+/**
+ * Figures out if we're building a browser bundle.
+ *
+ * @returns true if this is a browser bundle build.
+ */
+export function isBrowserBundle(): boolean {
+  return typeof __SENTRY_BROWSER_BUNDLE__ !== 'undefined' && !!__SENTRY_BROWSER_BUNDLE__;
+}

packages/utils/src/index.ts

@@ -17,3 +17,4 @@ export * from './string';
 export * from './supports';
 export * from './syncpromise';
 export * from './time';
+export * from './env';

packages/utils/src/node.ts

@@ -3,13 +3,20 @@
  * you must either a) use `console.log` rather than the logger, or b) put your function elsewhere.
  */
 
+import { isBrowserBundle } from './env';
+
 /**
  * Checks whether we're in the Node.js or Browser environment
  *
  * @returns Answer to given question
  */
 export function isNodeEnv(): boolean {
-  return Object.prototype.toString.call(typeof process !== 'undefined' ? process : 0) === '[object process]';
+  // explicitly check for browser bundles as those can be optimized statically
+  // by terser/rollup.
+  return (
+    !isBrowserBundle() &&
+    Object.prototype.toString.call(typeof process !== 'undefined' ? process : 0) === '[object process]'
+  );
 }
 
 /**