From 6c1fb7047f573e6b9716abbcbaa8e41f04a3322c Mon Sep 17 00:00:00 2001
From: Federico <me@fregante.com>
Date: Fri, 22 Nov 2024 15:39:31 +0700
Subject: [PATCH 1/8] Upgrade testing extension to MV3

---
 package-lock.json                     | 25 +++++++++++++++++++++----
 package.json                          |  3 ++-
 source/test/background.ts             |  8 ++++++++
 source/test/background/api.test.ts    |  2 +-
 source/test/background/testingApi.ts  |  8 +++-----
 source/test/contentscript/api.test.ts | 17 +++++++++--------
 source/test/iframe.html               |  6 +-----
 source/test/manifest.json             | 20 ++++++++++++--------
 source/test/options.html              |  4 +++-
 9 files changed, 60 insertions(+), 33 deletions(-)
 create mode 100644 source/test/background.ts

diff --git a/package-lock.json b/package-lock.json
index e777fef..b8ea7a6 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -13,7 +13,8 @@
         "p-retry": "^6.2.0",
         "serialize-error": "^11.0.3",
         "type-fest": "^4.26.1",
-        "webext-detect": "^5.1.0"
+        "webext-detect": "^5.3.1",
+        "webext-events": "^3.1.1"
       },
       "devDependencies": {
         "@parcel/config-webextension": "^2.11.0",
@@ -21318,9 +21319,25 @@
       }
     },
     "node_modules/webext-detect": {
-      "version": "5.1.0",
-      "resolved": "https://registry.npmjs.org/webext-detect/-/webext-detect-5.1.0.tgz",
-      "integrity": "sha512-nsTWw4xehwN5ztOctrK8WoREANGyFNemyE+8za8A7mBxHxpefQeCV/sIYL7JyT6aWclw3C6rqFU3FGHf4f0ASw==",
+      "version": "5.3.1",
+      "resolved": "https://registry.npmjs.org/webext-detect/-/webext-detect-5.3.1.tgz",
+      "integrity": "sha512-vmVd7haZ+CW/n037KUCi7t5Xn+oMxxScsgTPXirnHxXhHLJsR+4je9glh6QrsptgUfkZN4dGcFTrBrZUah1RAg==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=18"
+      },
+      "funding": {
+        "url": "https://github.com/sponsors/fregante"
+      }
+    },
+    "node_modules/webext-events": {
+      "version": "3.1.1",
+      "resolved": "https://registry.npmjs.org/webext-events/-/webext-events-3.1.1.tgz",
+      "integrity": "sha512-/QlXfa8LHcPOwLIycLglnHbXLqBOGetNn4pOyVJhV5UA6RifcP1tfkp8DYj3R6CjnHbjpSqFWXyc6dD4aTUcXw==",
+      "license": "MIT",
+      "dependencies": {
+        "webext-detect": "^5.0.2"
+      },
       "engines": {
         "node": ">=18"
       },
diff --git a/package.json b/package.json
index fa95ac8..832ef2c 100644
--- a/package.json
+++ b/package.json
@@ -30,7 +30,8 @@
     "p-retry": "^6.2.0",
     "serialize-error": "^11.0.3",
     "type-fest": "^4.26.1",
-    "webext-detect": "^5.1.0"
+    "webext-detect": "^5.3.1",
+    "webext-events": "^3.1.1"
   },
   "@parcel/resolver-default": {
     "packageExports": true
diff --git a/source/test/background.ts b/source/test/background.ts
new file mode 100644
index 0000000..fa4f600
--- /dev/null
+++ b/source/test/background.ts
@@ -0,0 +1,8 @@
+import "./webextensionPolyfill.js";
+import "./background/registration.ts";
+import "./contentscript/api.test.ts";
+import { onExtensionStart } from "webext-events";
+
+onExtensionStart.addListener(() => {
+  void browser.runtime.openOptionsPage();
+});
diff --git a/source/test/background/api.test.ts b/source/test/background/api.test.ts
index 39a0276..e46df69 100644
--- a/source/test/background/api.test.ts
+++ b/source/test/background/api.test.ts
@@ -58,7 +58,7 @@ test("should receive error from a background handler", async (t) => {
 
     t.equal(error.message, "This my error");
     t.true(
-      error.stack.includes("/background/registration.js"),
+      error.stack.includes("/background."),
       "The stacktrace must come from the background page"
     );
     t.true(
diff --git a/source/test/background/testingApi.ts b/source/test/background/testingApi.ts
index 73040a5..b760b61 100644
--- a/source/test/background/testingApi.ts
+++ b/source/test/background/testingApi.ts
@@ -2,11 +2,9 @@ import { executeFunction } from "webext-content-scripts";
 import { once } from "webext-messenger/shared.js";
 
 export async function ensureScripts(tabId: number): Promise<void> {
-  await browser.tabs.executeScript(tabId, {
-    file: "webextensionPolyfill.js",
-  });
-  await browser.tabs.executeScript(tabId, {
-    file: "contentscript/registration.js",
+  await browser.scripting.executeScript({
+    target: { tabId },
+    files: ["webextensionPolyfill.js", "contentscript/registration.js"],
   });
 }
 
diff --git a/source/test/contentscript/api.test.ts b/source/test/contentscript/api.test.ts
index 39b0c12..6e90ddc 100644
--- a/source/test/contentscript/api.test.ts
+++ b/source/test/contentscript/api.test.ts
@@ -48,7 +48,8 @@ function senderisBackground(
   t.true(
     sender?.origin === extensionUrl.origin || // Chrome
       sender?.origin === "null" || // Chrome, old
-      sender!.url?.endsWith("/_generated_background_page.html"), // Firefox
+      sender?.url?.includes("/background.") ||
+      sender?.url?.endsWith("/_generated_background_page.html"), // Firefox
     message
   );
 }
@@ -146,18 +147,18 @@ function runOnTarget(target: Target | PageTarget, expectedTitle: string) {
     const originalSender = trace[0];
     const directSender = trace.at(-1);
 
-    if (isContentScript() || !isBackground()) {
-      senderIsCurrentPage(
-        t,
-        originalSender,
-        "Messages should mention the current page in trace[0]"
-      );
-    } else {
+    if (isBackground()) {
       senderisBackground(
         t,
         directSender,
         "Messages should mention the current page (background) in trace[0]"
       );
+    } else {
+      senderIsCurrentPage(
+        t,
+        originalSender,
+        "Messages should mention the current page in trace[0]"
+      );
     }
 
     if (!("page" in target && isContentScript())) {
diff --git a/source/test/iframe.html b/source/test/iframe.html
index 07c9101..4aec5b0 100644
--- a/source/test/iframe.html
+++ b/source/test/iframe.html
@@ -2,11 +2,6 @@
 <meta charset="UTF-8" />
 <title>Extension frame</title>
 <style>
-  head,
-  title {
-    display: block;
-    font-size: 35px;
-  }
   iframe {
     display: block;
     margin: 20px 0;
@@ -14,3 +9,4 @@
 </style>
 <script type="module" src="webextensionPolyfill.ts"></script>
 <script type="module" src="contentscript/registration.ts"></script>
+<h1>Extension frame</h1>
diff --git a/source/test/manifest.json b/source/test/manifest.json
index ed283b7..31b197c 100644
--- a/source/test/manifest.json
+++ b/source/test/manifest.json
@@ -1,14 +1,13 @@
 {
+  "$schema": "https://json.schemastore.org/chrome-manifest",
   "name": "webext-messenger",
   "version": "0.0.0",
-  "manifest_version": 2,
-  "permissions": ["webNavigation", "https://fregante.github.io/*"],
+  "manifest_version": 3,
+  "permissions": ["webNavigation", "scripting", "storage"],
+  "host_permissions": ["https://fregante.github.io/*"],
   "background": {
-    "scripts": [
-      "webextensionPolyfill.ts",
-      "background/registration.ts",
-      "contentscript/api.test.ts"
-    ]
+    "type": "module",
+    "service_worker": "background.ts"
   },
   "options_ui": {
     "page": "options.html",
@@ -53,5 +52,10 @@
       "js": ["webextensionPolyfill.ts", "contentscript/missedRegistration.ts"]
     }
   ],
-  "web_accessible_resources": ["*.html", "**/*.ts"]
+  "web_accessible_resources": [
+    {
+      "resources": ["*.html", "**/*.ts"],
+      "matches": ["<all_urls>"]
+    }
+  ]
 }
diff --git a/source/test/options.html b/source/test/options.html
index f9df11d..966da58 100644
--- a/source/test/options.html
+++ b/source/test/options.html
@@ -1,5 +1,7 @@
-<!DOCTYPE html>
+<!doctype html>
 <meta charset="UTF-8" />
 <title>Options</title>
 <script type="module" src="webextensionPolyfill.ts"></script>
 <script type="module" src="background/api.test.ts"></script>
+<h1>Options page</h1>
+<p>Will call background methods</p>

From 7fcb705a50ca7f22e4dc7cf232078f0815e83216 Mon Sep 17 00:00:00 2001
From: Federico <me@fregante.com>
Date: Fri, 22 Nov 2024 16:06:22 +0700
Subject: [PATCH 2/8] Lint

---
 source/test/contentscript/api.test.ts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/source/test/contentscript/api.test.ts b/source/test/contentscript/api.test.ts
index 6e90ddc..ab3fa35 100644
--- a/source/test/contentscript/api.test.ts
+++ b/source/test/contentscript/api.test.ts
@@ -45,6 +45,7 @@ function senderisBackground(
   sender: Sender | undefined,
   message: string
 ) {
+  /* eslint-disable @typescript-eslint/prefer-nullish-coalescing -- It's an OR on falsy values */
   t.true(
     sender?.origin === extensionUrl.origin || // Chrome
       sender?.origin === "null" || // Chrome, old

From d79889ca17feb83110d87eddf0453474e71f0b48 Mon Sep 17 00:00:00 2001
From: Federico <me@fregante.com>
Date: Fri, 22 Nov 2024 15:11:12 +0700
Subject: [PATCH 3/8] Start offscreen

---
 package.json                          |  3 ++-
 source/test/background.ts             |  7 +++++++
 source/test/manifest.json             |  9 ++++++++-
 source/test/offscreen.html            |  5 +++++
 source/test/offscreen/addFrame.ts     |  5 +++++
 source/test/offscreen/api.test.ts     |  8 ++++++++
 source/test/offscreen/api.ts          |  7 +++++++
 source/test/offscreen/eval.ts         |  4 ++++
 source/test/offscreen/getLocation.ts  |  3 +++
 source/test/offscreen/getTrace.ts     |  5 +++++
 source/test/offscreen/registration.ts | 29 +++++++++++++++++++++++++++
 source/thisTarget.ts                  |  7 +++++--
 12 files changed, 88 insertions(+), 4 deletions(-)
 create mode 100644 source/test/offscreen.html
 create mode 100644 source/test/offscreen/addFrame.ts
 create mode 100644 source/test/offscreen/api.test.ts
 create mode 100644 source/test/offscreen/api.ts
 create mode 100644 source/test/offscreen/eval.ts
 create mode 100644 source/test/offscreen/getLocation.ts
 create mode 100644 source/test/offscreen/getTrace.ts
 create mode 100644 source/test/offscreen/registration.ts

diff --git a/package.json b/package.json
index 832ef2c..b50d701 100644
--- a/package.json
+++ b/package.json
@@ -74,7 +74,8 @@
     "run": {
       "startUrl": [
         "https://fregante.github.io/pixiebrix-testing-ground/Will-call-background-methods",
-        "https://fregante.github.io/pixiebrix-testing-ground/Will-call-other-CS-via-background"
+        "https://fregante.github.io/pixiebrix-testing-ground/Will-call-other-CS-via-background",
+        "https://fregante.github.io/pixiebrix-testing-ground/Will-offscreen-methods"
       ]
     }
   }
diff --git a/source/test/background.ts b/source/test/background.ts
index fa4f600..9620171 100644
--- a/source/test/background.ts
+++ b/source/test/background.ts
@@ -5,4 +5,11 @@ import { onExtensionStart } from "webext-events";
 
 onExtensionStart.addListener(() => {
   void browser.runtime.openOptionsPage();
+
+  void chrome.offscreen.createDocument({
+      url: 'offscreen.html',
+      // @ts-expect-error wrong?
+      reasons: ['DOM_PARSER'],
+      justification: 'testing'
+  });
 });
diff --git a/source/test/manifest.json b/source/test/manifest.json
index 31b197c..e8c5e38 100644
--- a/source/test/manifest.json
+++ b/source/test/manifest.json
@@ -3,7 +3,7 @@
   "name": "webext-messenger",
   "version": "0.0.0",
   "manifest_version": 3,
-  "permissions": ["webNavigation", "scripting", "storage"],
+  "permissions": ["webNavigation", "scripting", "storage", "offscreen"],
   "host_permissions": ["https://fregante.github.io/*"],
   "background": {
     "type": "module",
@@ -21,6 +21,13 @@
       ],
       "js": ["webextensionPolyfill.ts", "background/api.test.ts"]
     },
+    {
+      "all_frames": true,
+      "matches": [
+        "https://fregante.github.io/pixiebrix-testing-ground/Will-offscreen-methods"
+      ],
+      "js": ["webextensionPolyfill.ts", "offscreen/api.test.ts"]
+    },
     {
       "all_frames": true,
       "matches": [
diff --git a/source/test/offscreen.html b/source/test/offscreen.html
new file mode 100644
index 0000000..08c96c6
--- /dev/null
+++ b/source/test/offscreen.html
@@ -0,0 +1,5 @@
+<!DOCTYPE html>
+<meta charset="UTF-8" />
+<title>Offscreen page</title>
+<script type="module" src="webextensionPolyfill.ts"></script>
+<script type="module" src="offscreen/registration.ts"></script>
diff --git a/source/test/offscreen/addFrame.ts b/source/test/offscreen/addFrame.ts
new file mode 100644
index 0000000..0369ae1
--- /dev/null
+++ b/source/test/offscreen/addFrame.ts
@@ -0,0 +1,5 @@
+export function addFrame(): void {
+    const frame = document.createElement("iframe");
+    frame.src = "https://example.com";
+    document.body.append(frame);
+}
diff --git a/source/test/offscreen/api.test.ts b/source/test/offscreen/api.test.ts
new file mode 100644
index 0000000..1507801
--- /dev/null
+++ b/source/test/offscreen/api.test.ts
@@ -0,0 +1,8 @@
+import test from "tape";
+import {
+    getLocation,
+} from "./api.js";
+
+test("can get a value from the offscreen document", async (t) => {
+  t.equal(await getLocation(), "offscreen.html");
+});
diff --git a/source/test/offscreen/api.ts b/source/test/offscreen/api.ts
new file mode 100644
index 0000000..127bc01
--- /dev/null
+++ b/source/test/offscreen/api.ts
@@ -0,0 +1,7 @@
+import { getNotifier, getMethod } from "webext-messenger";
+
+const target = {page: "offscreen"};
+
+export const getLocation = getMethod("getLocation", target);
+export const addFrame = getNotifier("addFrame", target);
+export const getTrace = getMethod("getTrace", target);
diff --git a/source/test/offscreen/eval.ts b/source/test/offscreen/eval.ts
new file mode 100644
index 0000000..e9774c5
--- /dev/null
+++ b/source/test/offscreen/eval.ts
@@ -0,0 +1,4 @@
+export function evalScript(script: string): unknown {
+    // eslint-disable-next-line no-eval
+    return eval(script);
+}
diff --git a/source/test/offscreen/getLocation.ts b/source/test/offscreen/getLocation.ts
new file mode 100644
index 0000000..55ffa37
--- /dev/null
+++ b/source/test/offscreen/getLocation.ts
@@ -0,0 +1,3 @@
+export function getLocation(): string {
+    return location.href;
+}
diff --git a/source/test/offscreen/getTrace.ts b/source/test/offscreen/getTrace.ts
new file mode 100644
index 0000000..a23a5f4
--- /dev/null
+++ b/source/test/offscreen/getTrace.ts
@@ -0,0 +1,5 @@
+import { type MessengerMeta, type Sender } from "webext-messenger";
+
+export async function getTrace(this: MessengerMeta): Promise<Sender[]> {
+  return this.trace;
+}
diff --git a/source/test/offscreen/registration.ts b/source/test/offscreen/registration.ts
new file mode 100644
index 0000000..e8d8c53
--- /dev/null
+++ b/source/test/offscreen/registration.ts
@@ -0,0 +1,29 @@
+import { isOffscreenDocument } from "webext-detect";
+import { registerMethods } from "webext-messenger";
+
+import { addFrame } from "./addFrame.js";
+import { getLocation } from "./getLocation.js";
+import { getTrace } from "./getTrace.js";
+import { evalScript } from "./eval.js";
+
+declare global {
+  interface MessengerMethods {
+    addFrame: typeof addFrame;
+    getLocation: typeof getLocation;
+    getTrace: typeof getTrace;
+    eval: typeof evalScript;
+  }
+}
+
+if (!isOffscreenDocument()) {
+  throw new Error(
+    "This file must only be run in the offscreen document, which is the receiving end"
+  );
+}
+
+registerMethods({
+  addFrame,
+  getLocation,
+  getTrace,
+  eval: evalScript,
+});
diff --git a/source/thisTarget.ts b/source/thisTarget.ts
index a680155..7114280 100644
--- a/source/thisTarget.ts
+++ b/source/thisTarget.ts
@@ -2,6 +2,7 @@ import {
   getContextName,
   isBackground,
   isExtensionContext,
+  isOffscreenDocument,
 } from "webext-detect";
 import { messenger } from "./sender.js";
 import { registerMethods } from "./receiver.js";
@@ -41,6 +42,8 @@ import { pEvent } from "p-event";
 // If a message is received before this is ready, it will just have to be ignored.
 export const thisTarget: KnownTarget = isBackground()
   ? { page: "background" }
+  : (isOffscreenDocument()
+  ? { page: "offscreen" }
   : {
       get page(): string {
         // Extension pages have relative URLs to simplify comparison
@@ -51,11 +54,11 @@ export const thisTarget: KnownTarget = isBackground()
         // Don't use the hash
         return origin + location.pathname + location.search;
       },
-    };
+    });
 
 let tabDataStatus: "needed" | "pending" | "received" | "not-needed" | "error" =
   // The background page doesn't have a tab
-  isBackground() ? "not-needed" : "needed";
+  isBackground() || isOffscreenDocument() ? "not-needed" : "needed";
 
 export function getTabDataStatus(): typeof tabDataStatus {
   return tabDataStatus;

From 672e856fdff1fcf586059a6621a460a35b0cb97a Mon Sep 17 00:00:00 2001
From: Federico <me@fregante.com>
Date: Fri, 22 Nov 2024 16:38:11 +0700
Subject: [PATCH 4/8] Finalize offscreen

---
 package.json                          |  2 +-
 source/test/background.ts             | 15 +++++---------
 source/test/contentscript/api.test.ts | 29 +++------------------------
 source/test/helpers.ts                | 27 +++++++++++++++++++++++++
 source/test/manifest.json             |  3 +--
 source/test/offscreen/api.test.ts     | 28 ++++++++++++++++++++++++--
 source/test/offscreen/eval.ts         |  4 ----
 source/test/offscreen/registration.ts |  3 ---
 8 files changed, 63 insertions(+), 48 deletions(-)
 delete mode 100644 source/test/offscreen/eval.ts

diff --git a/package.json b/package.json
index b50d701..5669c48 100644
--- a/package.json
+++ b/package.json
@@ -75,7 +75,7 @@
       "startUrl": [
         "https://fregante.github.io/pixiebrix-testing-ground/Will-call-background-methods",
         "https://fregante.github.io/pixiebrix-testing-ground/Will-call-other-CS-via-background",
-        "https://fregante.github.io/pixiebrix-testing-ground/Will-offscreen-methods"
+        "https://fregante.github.io/pixiebrix-testing-ground/Will-call-offscreen-methods"
       ]
     }
   }
diff --git a/source/test/background.ts b/source/test/background.ts
index 9620171..abf69ee 100644
--- a/source/test/background.ts
+++ b/source/test/background.ts
@@ -1,15 +1,10 @@
 import "./webextensionPolyfill.js";
 import "./background/registration.ts";
 import "./contentscript/api.test.ts";
-import { onExtensionStart } from "webext-events";
 
-onExtensionStart.addListener(() => {
-  void browser.runtime.openOptionsPage();
-
-  void chrome.offscreen.createDocument({
-      url: 'offscreen.html',
-      // @ts-expect-error wrong?
-      reasons: ['DOM_PARSER'],
-      justification: 'testing'
-  });
+void chrome.offscreen.createDocument({
+    url: 'offscreen.html',
+    // @ts-expect-error wrong?
+    reasons: ['DOM_PARSER'],
+    justification: 'testing'
 });
diff --git a/source/test/contentscript/api.test.ts b/source/test/contentscript/api.test.ts
index ab3fa35..57ac8f2 100644
--- a/source/test/contentscript/api.test.ts
+++ b/source/test/contentscript/api.test.ts
@@ -1,6 +1,6 @@
 import test from "tape";
 import { isBackground, isContentScript, isWebPage } from "webext-detect";
-import { type PageTarget, type Sender, type Target } from "webext-messenger";
+import { type PageTarget, type Target } from "webext-messenger";
 import {
   errorTabDoesntExist,
   errorTargetClosedEarly,
@@ -12,6 +12,8 @@ import {
   sleep,
   trackSettleTime,
   expectDuration,
+  senderisBackground,
+  senderIsCurrentPage,
 } from "../helpers.js";
 import * as backgroundContext from "../background/api.js";
 import * as localContext from "../background/testingApi.js";
@@ -30,31 +32,6 @@ import {
 } from "./api.js";
 import { MessengerError } from "../../shared.js";
 
-const extensionUrl = new URL(chrome.runtime.getURL(""));
-
-function senderIsCurrentPage(
-  t: test.Test,
-  sender: Sender | undefined,
-  message: string
-) {
-  t.equal(sender?.url, location.href, message);
-}
-
-function senderisBackground(
-  t: test.Test,
-  sender: Sender | undefined,
-  message: string
-) {
-  /* eslint-disable @typescript-eslint/prefer-nullish-coalescing -- It's an OR on falsy values */
-  t.true(
-    sender?.origin === extensionUrl.origin || // Chrome
-      sender?.origin === "null" || // Chrome, old
-      sender?.url?.includes("/background.") ||
-      sender?.url?.endsWith("/_generated_background_page.html"), // Firefox
-    message
-  );
-}
-
 const { openTab, createTargets, ensureScripts, closeTab } = isBackground()
   ? localContext
   : backgroundContext;
diff --git a/source/test/helpers.ts b/source/test/helpers.ts
index cef484a..3239cce 100644
--- a/source/test/helpers.ts
+++ b/source/test/helpers.ts
@@ -1,4 +1,6 @@
 import type test from "tape";
+import { type Sender } from "webext-messenger";
+
 
 export async function expectRejection(
   t: test.Test,
@@ -65,3 +67,28 @@ export function expectDuration(
     );
   }
 }
+
+const extensionUrl = new URL(chrome.runtime.getURL(""));
+
+export function senderIsCurrentPage(
+  t: test.Test,
+  sender: Sender | undefined,
+  message: string
+) {
+  t.equal(sender?.url, location.href, message);
+}
+
+export function senderisBackground(
+  t: test.Test,
+  sender: Sender | undefined,
+  message: string
+) {
+  /* eslint-disable @typescript-eslint/prefer-nullish-coalescing -- It's an OR on falsy values */
+  t.true(
+    sender?.origin === extensionUrl.origin || // Chrome
+      sender?.origin === "null" || // Chrome, old
+      sender?.url?.includes("/background.") ||
+      sender?.url?.endsWith("/_generated_background_page.html"), // Firefox
+    message
+  );
+}
diff --git a/source/test/manifest.json b/source/test/manifest.json
index e8c5e38..fed14c1 100644
--- a/source/test/manifest.json
+++ b/source/test/manifest.json
@@ -22,9 +22,8 @@
       "js": ["webextensionPolyfill.ts", "background/api.test.ts"]
     },
     {
-      "all_frames": true,
       "matches": [
-        "https://fregante.github.io/pixiebrix-testing-ground/Will-offscreen-methods"
+        "https://fregante.github.io/pixiebrix-testing-ground/Will-call-offscreen-methods"
       ],
       "js": ["webextensionPolyfill.ts", "offscreen/api.test.ts"]
     },
diff --git a/source/test/offscreen/api.test.ts b/source/test/offscreen/api.test.ts
index 1507801..03f76f0 100644
--- a/source/test/offscreen/api.test.ts
+++ b/source/test/offscreen/api.test.ts
@@ -1,8 +1,32 @@
 import test from "tape";
 import {
     getLocation,
+    addFrame,
+    getTrace,
 } from "./api.js";
+import { senderIsCurrentPage } from "../helpers.js";
 
-test("can get a value from the offscreen document", async (t) => {
-  t.equal(await getLocation(), "offscreen.html");
+test("should get a value from the offscreen document", async (t) => {
+  t.equal(await getLocation(), chrome.runtime.getURL( "offscreen.html"));
+});
+
+test("notification should return undefined", async (t) => {
+  // eslint-disable-next-line @typescript-eslint/no-confusing-void-expression -- Testing for this specifically
+  t.equals(addFrame(), undefined);
+});
+
+test("should receive trace", async (t) => {
+  const trace = await getTrace();
+  t.true(Array.isArray(trace));
+
+  const originalSender = trace[0];
+
+
+  senderIsCurrentPage(
+    t,
+    originalSender,
+    "Messages should mention the current page in trace[0]"
+  );
+
+  t.equal(trace.length, 1, "The offscreen page can and should only be messaged directly");
 });
diff --git a/source/test/offscreen/eval.ts b/source/test/offscreen/eval.ts
deleted file mode 100644
index e9774c5..0000000
--- a/source/test/offscreen/eval.ts
+++ /dev/null
@@ -1,4 +0,0 @@
-export function evalScript(script: string): unknown {
-    // eslint-disable-next-line no-eval
-    return eval(script);
-}
diff --git a/source/test/offscreen/registration.ts b/source/test/offscreen/registration.ts
index e8d8c53..35e00eb 100644
--- a/source/test/offscreen/registration.ts
+++ b/source/test/offscreen/registration.ts
@@ -4,14 +4,12 @@ import { registerMethods } from "webext-messenger";
 import { addFrame } from "./addFrame.js";
 import { getLocation } from "./getLocation.js";
 import { getTrace } from "./getTrace.js";
-import { evalScript } from "./eval.js";
 
 declare global {
   interface MessengerMethods {
     addFrame: typeof addFrame;
     getLocation: typeof getLocation;
     getTrace: typeof getTrace;
-    eval: typeof evalScript;
   }
 }
 
@@ -25,5 +23,4 @@ registerMethods({
   addFrame,
   getLocation,
   getTrace,
-  eval: evalScript,
 });

From ec40e28208cd3057932ba83a307d43be4c833a86 Mon Sep 17 00:00:00 2001
From: Federico <me@fregante.com>
Date: Thu, 28 Nov 2024 12:34:39 +0700
Subject: [PATCH 5/8] Prettier

---
 source/test/background.ts             |  8 ++++----
 source/test/helpers.ts                |  7 +++----
 source/test/offscreen.html            |  2 +-
 source/test/offscreen/addFrame.ts     |  6 +++---
 source/test/offscreen/api.test.ts     | 17 ++++++++---------
 source/test/offscreen/api.ts          |  2 +-
 source/test/offscreen/getLocation.ts  |  2 +-
 source/test/offscreen/registration.ts |  2 +-
 source/thisTarget.ts                  | 26 +++++++++++++-------------
 9 files changed, 35 insertions(+), 37 deletions(-)

diff --git a/source/test/background.ts b/source/test/background.ts
index abf69ee..983811d 100644
--- a/source/test/background.ts
+++ b/source/test/background.ts
@@ -3,8 +3,8 @@ import "./background/registration.ts";
 import "./contentscript/api.test.ts";
 
 void chrome.offscreen.createDocument({
-    url: 'offscreen.html',
-    // @ts-expect-error wrong?
-    reasons: ['DOM_PARSER'],
-    justification: 'testing'
+  url: "offscreen.html",
+  // @ts-expect-error wrong?
+  reasons: ["DOM_PARSER"],
+  justification: "testing",
 });
diff --git a/source/test/helpers.ts b/source/test/helpers.ts
index c7ad210..ab23c71 100644
--- a/source/test/helpers.ts
+++ b/source/test/helpers.ts
@@ -1,7 +1,6 @@
 import type test from "tape";
 import { type Sender } from "webext-messenger";
 
-
 export async function expectRejection(
   t: test.Test,
   promise: Promise<unknown>,
@@ -73,7 +72,7 @@ const extensionUrl = new URL(chrome.runtime.getURL(""));
 export function senderIsCurrentPage(
   t: test.Test,
   sender: Sender | undefined,
-  message: string
+  message: string,
 ) {
   t.equal(sender?.url, location.href, message);
 }
@@ -81,7 +80,7 @@ export function senderIsCurrentPage(
 export function senderisBackground(
   t: test.Test,
   sender: Sender | undefined,
-  message: string
+  message: string,
 ) {
   /* eslint-disable @typescript-eslint/prefer-nullish-coalescing -- It's an OR on falsy values */
   t.true(
@@ -89,6 +88,6 @@ export function senderisBackground(
       sender?.origin === "null" || // Chrome, old
       sender?.url?.includes("/background.") ||
       sender?.url?.endsWith("/_generated_background_page.html"), // Firefox
-    message
+    message,
   );
 }
diff --git a/source/test/offscreen.html b/source/test/offscreen.html
index 08c96c6..4281c34 100644
--- a/source/test/offscreen.html
+++ b/source/test/offscreen.html
@@ -1,4 +1,4 @@
-<!DOCTYPE html>
+<!doctype html>
 <meta charset="UTF-8" />
 <title>Offscreen page</title>
 <script type="module" src="webextensionPolyfill.ts"></script>
diff --git a/source/test/offscreen/addFrame.ts b/source/test/offscreen/addFrame.ts
index 0369ae1..364c597 100644
--- a/source/test/offscreen/addFrame.ts
+++ b/source/test/offscreen/addFrame.ts
@@ -1,5 +1,5 @@
 export function addFrame(): void {
-    const frame = document.createElement("iframe");
-    frame.src = "https://example.com";
-    document.body.append(frame);
+  const frame = document.createElement("iframe");
+  frame.src = "https://example.com";
+  document.body.append(frame);
 }
diff --git a/source/test/offscreen/api.test.ts b/source/test/offscreen/api.test.ts
index 03f76f0..a36b818 100644
--- a/source/test/offscreen/api.test.ts
+++ b/source/test/offscreen/api.test.ts
@@ -1,13 +1,9 @@
 import test from "tape";
-import {
-    getLocation,
-    addFrame,
-    getTrace,
-} from "./api.js";
+import { getLocation, addFrame, getTrace } from "./api.js";
 import { senderIsCurrentPage } from "../helpers.js";
 
 test("should get a value from the offscreen document", async (t) => {
-  t.equal(await getLocation(), chrome.runtime.getURL( "offscreen.html"));
+  t.equal(await getLocation(), chrome.runtime.getURL("offscreen.html"));
 });
 
 test("notification should return undefined", async (t) => {
@@ -21,12 +17,15 @@ test("should receive trace", async (t) => {
 
   const originalSender = trace[0];
 
-
   senderIsCurrentPage(
     t,
     originalSender,
-    "Messages should mention the current page in trace[0]"
+    "Messages should mention the current page in trace[0]",
   );
 
-  t.equal(trace.length, 1, "The offscreen page can and should only be messaged directly");
+  t.equal(
+    trace.length,
+    1,
+    "The offscreen page can and should only be messaged directly",
+  );
 });
diff --git a/source/test/offscreen/api.ts b/source/test/offscreen/api.ts
index 127bc01..6563481 100644
--- a/source/test/offscreen/api.ts
+++ b/source/test/offscreen/api.ts
@@ -1,6 +1,6 @@
 import { getNotifier, getMethod } from "webext-messenger";
 
-const target = {page: "offscreen"};
+const target = { page: "offscreen" };
 
 export const getLocation = getMethod("getLocation", target);
 export const addFrame = getNotifier("addFrame", target);
diff --git a/source/test/offscreen/getLocation.ts b/source/test/offscreen/getLocation.ts
index 55ffa37..6ce6ddd 100644
--- a/source/test/offscreen/getLocation.ts
+++ b/source/test/offscreen/getLocation.ts
@@ -1,3 +1,3 @@
 export function getLocation(): string {
-    return location.href;
+  return location.href;
 }
diff --git a/source/test/offscreen/registration.ts b/source/test/offscreen/registration.ts
index 35e00eb..b2fe14c 100644
--- a/source/test/offscreen/registration.ts
+++ b/source/test/offscreen/registration.ts
@@ -15,7 +15,7 @@ declare global {
 
 if (!isOffscreenDocument()) {
   throw new Error(
-    "This file must only be run in the offscreen document, which is the receiving end"
+    "This file must only be run in the offscreen document, which is the receiving end",
   );
 }
 
diff --git a/source/thisTarget.ts b/source/thisTarget.ts
index 12b0683..826ca2d 100644
--- a/source/thisTarget.ts
+++ b/source/thisTarget.ts
@@ -42,19 +42,19 @@ import { pEvent } from "p-event";
 // If a message is received before this is ready, it will just have to be ignored.
 export const thisTarget: KnownTarget = isBackground()
   ? { page: "background" }
-  : (isOffscreenDocument()
-  ? { page: "offscreen" }
-  : {
-      get page(): string {
-        // Extension pages have relative URLs to simplify comparison
-        const origin = location.protocol.startsWith("http")
-          ? location.origin
-          : "";
-
-        // Don't use the hash
-        return origin + location.pathname + location.search;
-      },
-    });
+  : isOffscreenDocument()
+    ? { page: "offscreen" }
+    : {
+        get page(): string {
+          // Extension pages have relative URLs to simplify comparison
+          const origin = location.protocol.startsWith("http")
+            ? location.origin
+            : "";
+
+          // Don't use the hash
+          return origin + location.pathname + location.search;
+        },
+      };
 
 let tabDataStatus: "needed" | "pending" | "received" | "not-needed" | "error" =
   // The background page doesn't have a tab

From 465b7a0205023678820c65f0bfd4a3617891b6f9 Mon Sep 17 00:00:00 2001
From: Federico <me@fregante.com>
Date: Thu, 28 Nov 2024 13:00:38 +0700
Subject: [PATCH 6/8] Silence `offscreen.createDocument`

---
 source/test/background.ts | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/source/test/background.ts b/source/test/background.ts
index 983811d..1233cb6 100644
--- a/source/test/background.ts
+++ b/source/test/background.ts
@@ -2,9 +2,20 @@ import "./webextensionPolyfill.js";
 import "./background/registration.ts";
 import "./contentscript/api.test.ts";
 
-void chrome.offscreen.createDocument({
-  url: "offscreen.html",
-  // @ts-expect-error wrong?
-  reasons: ["DOM_PARSER"],
-  justification: "testing",
-});
+async function init() {
+  try {
+    await chrome.offscreen.createDocument({
+      url: "offscreen.html",
+      // @ts-expect-error wrong?
+      reasons: ["DOM_PARSER"],
+      justification: "testing",
+    });
+  } catch (error) {
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-call, @typescript-eslint/no-explicit-any
+    if (!(error as any).message.includes("Only a single offscreen")) {
+      throw error;
+    }
+  }
+}
+
+void init();

From 1c21875840e24542bc092ac336532bcb8c73fa9d Mon Sep 17 00:00:00 2001
From: Federico <me@fregante.com>
Date: Thu, 28 Nov 2024 15:02:18 +0700
Subject: [PATCH 7/8] Lint

---
 .eslintrc | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.eslintrc b/.eslintrc
index 7dd2ffe..7ef4a4c 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -50,6 +50,7 @@
         }
       }
     ],
+    "unicorn/no-nested-ternary": "off", // Prettier conflict
     "@typescript-eslint/consistent-type-definitions": "off" // Unconvinced by its utility; may be counterproductive
   },
   "overrides": [

From be8bbb20a04455adf9fe5997a56854997a9bd678 Mon Sep 17 00:00:00 2001
From: Federico <me@fregante.com>
Date: Mon, 2 Dec 2024 21:08:50 +0700
Subject: [PATCH 8/8] PR review

---
 source/test/contentscript/api.test.ts |  6 ++---
 source/test/helpers.ts                |  2 +-
 source/thisTarget.ts                  | 32 +++++++++++++--------------
 3 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/source/test/contentscript/api.test.ts b/source/test/contentscript/api.test.ts
index 7f39c28..62d7320 100644
--- a/source/test/contentscript/api.test.ts
+++ b/source/test/contentscript/api.test.ts
@@ -12,7 +12,7 @@ import {
   sleep,
   trackSettleTime,
   expectDuration,
-  senderisBackground,
+  senderIsBackground,
   senderIsCurrentPage,
 } from "../helpers.js";
 import * as backgroundContext from "../background/api.js";
@@ -126,7 +126,7 @@ function runOnTarget(target: Target | PageTarget, expectedTitle: string) {
     const directSender = trace.at(-1);
 
     if (isBackground()) {
-      senderisBackground(
+      senderIsBackground(
         t,
         originalSender,
         "Messages should mention the current page (background) in trace[0]",
@@ -140,7 +140,7 @@ function runOnTarget(target: Target | PageTarget, expectedTitle: string) {
     }
 
     if (!("page" in target && isContentScript())) {
-      senderisBackground(
+      senderIsBackground(
         t,
         directSender,
         "Messages originated in content scripts or background pages must come directly from the background page",
diff --git a/source/test/helpers.ts b/source/test/helpers.ts
index ab23c71..e4d2da8 100644
--- a/source/test/helpers.ts
+++ b/source/test/helpers.ts
@@ -77,7 +77,7 @@ export function senderIsCurrentPage(
   t.equal(sender?.url, location.href, message);
 }
 
-export function senderisBackground(
+export function senderIsBackground(
   t: test.Test,
   sender: Sender | undefined,
   message: string,
diff --git a/source/thisTarget.ts b/source/thisTarget.ts
index 826ca2d..3b2d69c 100644
--- a/source/thisTarget.ts
+++ b/source/thisTarget.ts
@@ -40,24 +40,24 @@ import { pEvent } from "p-event";
 // Soft warning: Race conditions are possible.
 // This CANNOT be awaited because waiting for it means "I will handle the message."
 // If a message is received before this is ready, it will just have to be ignored.
-export const thisTarget: KnownTarget = isBackground()
-  ? { page: "background" }
-  : isOffscreenDocument()
-    ? { page: "offscreen" }
-    : {
-        get page(): string {
-          // Extension pages have relative URLs to simplify comparison
-          const origin = location.protocol.startsWith("http")
-            ? location.origin
-            : "";
-
-          // Don't use the hash
-          return origin + location.pathname + location.search;
-        },
-      };
+export const thisTarget: KnownTarget = (() => {
+  if (isBackground()) return { page: "background" };
+  if (isOffscreenDocument()) return { page: "offscreen" };
+  return {
+    get page(): string {
+      // Extension pages have relative URLs to simplify comparison
+      const origin = location.protocol.startsWith("http")
+        ? location.origin
+        : "";
+
+      // Don't use the hash
+      return origin + location.pathname + location.search;
+    },
+  };
+})();
 
 let tabDataStatus: "needed" | "pending" | "received" | "not-needed" | "error" =
-  // The background page doesn't have a tab
+  // Exclude contexts that don't have a tab associated to them
   isBackground() || isOffscreenDocument() ? "not-needed" : "needed";
 
 export function getTabDataStatus(): typeof tabDataStatus {