Implement custom Jest environment for Miniflare

Author: mrbbot

package-lock.json

@@ -178,8 +178,9 @@ function throwNoScriptError(modules?: boolean) {
 export interface MiniflareCoreContext {
   log: Log;
   storageFactory: StorageFactory;
-  scriptRunner: ScriptRunner;
+  scriptRunner?: ScriptRunner;
   scriptRequired?: boolean;
+  scriptRunForModuleExports?: boolean;
   defaultConfigPath?: string;
 }
 
@@ -204,8 +205,9 @@ export class MiniflareCore<
   readonly log: Log;
   readonly #storage: StorageFactory;
   readonly #pluginStorages: PluginData<Plugins, PluginStorageFactory>;
-  readonly #scriptRunner: ScriptRunner;
+  readonly #scriptRunner?: ScriptRunner;
   readonly #scriptRequired?: boolean;
+  readonly #scriptRunForModuleExports?: boolean;
   readonly #defaultConfigPath: string;
 
   #compat?: Compatibility;
@@ -219,6 +221,7 @@ export class MiniflareCore<
   readonly #scriptWatchPaths = new Set<string>();
 
   #globalScope?: ServiceWorkerGlobalScope;
+  #bindings?: Context;
   #watcher?: Watcher;
   #watcherCallbackMutex?: Mutex;
   #previousWatchPaths?: Set<string>;
@@ -238,6 +241,7 @@ export class MiniflareCore<
     this.#pluginStorages = new Map<keyof Plugins, PluginStorageFactory>();
     this.#scriptRunner = ctx.scriptRunner;
     this.#scriptRequired = ctx.scriptRequired;
+    this.#scriptRunForModuleExports = ctx.scriptRunForModuleExports;
     this.#defaultConfigPath = ctx.defaultConfigPath ?? "wrangler.toml";
 
     this.#initPromise = this.#init().then(() => this.#reload());
@@ -271,11 +275,7 @@ export class MiniflareCore<
     this.log.verbose(`- setup(${name})`);
     const result = await instance.setup(this.getPluginStorage(name));
     this.#updateWatch(this.#setupWatch!, name, result);
-    this.#setupResults!.set(name, {
-      globals: result?.globals,
-      bindings: result?.bindings,
-      script: result?.script,
-    });
+    this.#setupResults!.set(name, result ?? {});
     return true;
   }
 
@@ -410,6 +410,7 @@ export class MiniflareCore<
     if (this.#wranglerConfigPath) newWatchPaths.add(this.#wranglerConfigPath);
 
     let script: ScriptBlueprint | undefined = undefined;
+    let requiresModuleExports = false;
     for (const [name] of this.#plugins) {
       // Run beforeReload hook
       const instance = this.#instances![name];
@@ -428,6 +429,7 @@ export class MiniflareCore<
         }
         script = result.script;
       }
+      if (result?.requiresModuleExports) requiresModuleExports = true;
 
       // Extract watch paths
       const beforeSetupWatch = this.#beforeSetupWatch!.get(name);
@@ -447,11 +449,22 @@ export class MiniflareCore<
       modules
     );
     this.#globalScope = globalScope;
+    this.#bindings = bindings;
 
     // Run script blueprints, with modules rules if in modules mode
     const rules = modules ? processedModuleRules : undefined;
     let res: ScriptRunnerResult | undefined = undefined;
-    if (script) {
+    if (
+      // Run the script if we've got one...
+      script &&
+      // ...and either we're always running it, or we're in modules mode
+      // and require its exports
+      (!this.#scriptRunForModuleExports || (modules && requiresModuleExports))
+    ) {
+      if (!this.#scriptRunner) {
+        throw new TypeError("Running scripts requires a script runner");
+      }
+
       this.log.verbose("Running script...");
       res = await this.#scriptRunner.run(globalScope, script, rules);
 
@@ -638,6 +651,11 @@ export class MiniflareCore<
     return this.#globalScope!;
   }
 
+  async getBindings(): Promise<Context> {
+    await this.#initPromise;
+    return this.#bindings!;
+  }
+
   async dispatchFetch<WaitUntil extends any[] = unknown[]>(
     input: RequestInfo,
     init?: RequestInit

packages/core/src/index.ts

@@ -14,6 +14,7 @@ import {
   RequestInit,
   _deepEqual,
 } from "@miniflare/core";
+import { DurableObjectsPlugin } from "@miniflare/durable-objects";
 import { VMScriptRunner } from "@miniflare/runner-vm";
 import {
   Context,
@@ -598,6 +599,37 @@ test("MiniflareCore: #reload: throws if multiple plugins return scripts", async
     message: "Multiple plugins returned a script",
   });
 });
+test("MiniflareCore: #reload: only runs script if module exports needed when scriptRunForModuleExports set", async (t) => {
+  const log = new NoOpLog();
+  const storageFactory = new MemoryStorageFactory();
+  const ctx: MiniflareCoreContext = {
+    log,
+    storageFactory,
+    scriptRunner,
+    scriptRunForModuleExports: true,
+  };
+
+  let calledback = false;
+  const plugins = { CorePlugin, BindingsPlugin, DurableObjectsPlugin };
+  const globals = { callback: () => (calledback = true) };
+  const script = "callback(); export class TestObject {}";
+  let mf = new MiniflareCore(plugins, ctx, {
+    modules: true,
+    script,
+    globals,
+  });
+  await mf.getPlugins(); // Allow script to run
+  t.false(calledback);
+
+  mf = new MiniflareCore(plugins, ctx, {
+    modules: true,
+    script,
+    globals,
+    durableObjects: { TEST: "TestObject" },
+  });
+  await mf.getPlugins(); // Allow script to run
+  t.true(calledback);
+});
 test("MiniflareCore: #reload: watches files", async (t) => {
   const log = new TestLog();
   const tmp = await useTmp(t);
@@ -932,6 +964,15 @@ test("MiniflareCore: getGlobalScope: gets mutable global scope", async (t) => {
   t.is(await res.text(), "value2,test");
 });
 
+test("MiniflareCore: getBindings: gets bindings", async (t) => {
+  const mf = useMiniflare(
+    { BindingsPlugin },
+    { bindings: { KEY1: "value1" }, globals: { KEY2: "value2" } }
+  );
+  const bindings = await mf.getBindings();
+  t.deepEqual(bindings, { KEY1: "value1" });
+});
+
 // Just testing dispatchFetch/dispatchScheduled parameter normalisation and
 // pass-through here, more tests in standards/event.spec.ts
 const dispatchFetchMacro: Macro<[input: RequestInfo, init?: RequestInit]> =

packages/core/test/index.spec.ts

@@ -165,7 +165,10 @@ export class DurableObjectsPlugin
       // TODO: get namespace from scriptName instance, maybe watch it?
       bindings[name] = this.getNamespace(storageFactory, name);
     }
-    return { bindings };
+    return {
+      bindings,
+      requiresModuleExports: this.#processedObjects.length > 0,
+    };
   }
 
   beforeReload(): void {

packages/durable-objects/src/plugin.ts

@@ -1,6 +1,6 @@
 {
   "private": true,
-  "name": "@miniflare/jest",
+  "name": "jest-environment-miniflare",
   "version": "2.0.0-next.3",
   "description": "Jest testing module for Miniflare: a fun, full-featured, fully-local simulator for Cloudflare Workers",
   "keywords": [
@@ -37,8 +37,16 @@
     "extends": "../../package.json"
   },
   "dependencies": {
+    "@miniflare/cache": "2.0.0-next.3",
     "@miniflare/core": "2.0.0-next.3",
+    "@miniflare/durable-objects": "2.0.0-next.3",
+    "@miniflare/html-rewriter": "2.0.0-next.3",
+    "@miniflare/kv": "2.0.0-next.3",
+    "@miniflare/runner-vm": "2.0.0-next.3",
     "@miniflare/shared": "2.0.0-next.3",
+    "@miniflare/sites": "2.0.0-next.3",
+    "@miniflare/storage-memory": "2.0.0-next.3",
+    "@miniflare/web-sockets": "2.0.0-next.3",
     "miniflare": "2.0.0-next.3"
   },
   "peerDependencies": {