Turn several PR comments from #8347 into code comments.

src/utilities/fixes/__DEV__.ts

@@ -6,6 +6,9 @@ function getDEV() {
     return Boolean(__DEV__);
   } catch {
     Object.defineProperty(global, "__DEV__", {
+      // In a buildless browser environment, maybe(() => process.env.NODE_ENV)
+      // evaluates as undefined, so __DEV__ becomes true by default, but can be
+      // initialized to false instead by a script/module that runs earlier.
       value: maybe(() => process.env.NODE_ENV) !== "production",
       enumerable: false,
       configurable: true,

src/utilities/fixes/graphql.ts

@@ -1,7 +1,14 @@
+// The ordering of these imports is important, because it ensures the temporary
+// process.env.NODE_ENV polyfill is defined globally (if necessary) before we
+// import { isType } from 'graphql'. The instanceOf function that we really care
+// about (the one that uses process.env.NODE_ENV) is not exported from the
+// top-level graphql package, but isType uses instanceOf, and is exported.
 import { undo } from './process';
 import { isType } from 'graphql';
 
 export function applyFixes() {
+  // Calling isType here just to make sure it won't be tree-shaken away,
+  // provided applyFixes is called elsewhere.
   isType(null);
   return undo();
 }

src/utilities/fixes/index.ts

@@ -1,3 +1,12 @@
-export { default as __DEV__ } from "./__DEV__";
+// Just in case the graphql package switches from process.env.NODE_ENV to
+// __DEV__, make sure __DEV__ is polyfilled before importing graphql.
+import { default as __DEV__ } from "./__DEV__";
+export { __DEV__ }
+
+// Import graphql/jsutils/instanceOf safely, working around its unchecked usage
+// of process.env.NODE_ENV and https://github.com/graphql/graphql-js/pull/2894.
 import { applyFixes } from "./graphql";
+
+// Synchronously undo the global process.env.NODE_ENV polyfill that we created
+// temporarily while importing the offending graphql/jsutils/instanceOf module.
 applyFixes();

src/utilities/fixes/process.ts

@@ -7,6 +7,9 @@ let needToUndo = false;
 if (global && maybe(() => process.env.NODE_ENV) === void 0) {
   const stub = {
     env: {
+      // This default needs to be "production" instead of "development", to
+      // avoid the problem https://github.com/graphql/graphql-js/pull/2894 will
+      // eventually solve, once merged.
       NODE_ENV: "production",
     },
   };