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Handle closed tabs better while attempting to message them #3572

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merged 1 commit into from
Jun 6, 2022
Merged

Handle closed tabs better while attempting to message them #3572

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68 changes: 35 additions & 33 deletions package-lock.json
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2 changes: 1 addition & 1 deletion package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -149,7 +149,7 @@
"webext-content-scripts": "^1.0.1",
"webext-detect-page": "^4.0.1",
"webext-dynamic-content-scripts": "^8.1.1",
"webext-messenger": "^0.18.2",
"webext-messenger": "^0.19.1",
"webext-patterns": "^1.1.1",
"webext-polyfill-kinda": "^0.10.0",
"webext-tools": "^1.0.0",
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37 changes: 20 additions & 17 deletions src/background/executor.ts
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Expand Up @@ -20,42 +20,45 @@ import { expectContext } from "@/utils/expectContext";
import { asyncForEach } from "@/utils";
import { getLinkedApiClient } from "@/services/apiClient";
import { JsonObject } from "type-fest";
import { MessengerMeta } from "webext-messenger";
import {
MessengerMeta,
errorTargetClosedEarly,
errorTabDoesntExist,
} from "webext-messenger";
import { runBrick } from "@/contentScript/messenger/api";
import { Target } from "@/types";
import { RemoteExecutionError } from "@/blocks/errors";
import pDefer from "p-defer";
import { canAccessTab } from "webext-tools";
import { onTabClose } from "@/chrome";
import { getErrorMessage } from "@/errors/errorHelpers";
// eslint-disable-next-line import/no-restricted-paths -- Type only
import type { RunBlock } from "@/contentScript/runBlockTypes";
import { BusinessError } from "@/errors/businessErrors";

type TabId = number;

// Used to determine which promise was resolved in a race
const TYPE_WAS_CLOSED = Symbol("Tab was closed");

const tabToOpener = new Map<TabId, TabId>();
const tabToTarget = new Map<TabId, TabId>();
// TODO: One tab could have multiple targets, but `tabToTarget` currenly only supports one at a time

async function safelyRunBrick({ tabId }: { tabId: number }, request: RunBlock) {
if (!(await canAccessTab(tabId))) {
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Since this was being run first, it was reporting "no access" when the tab just didn't exist (was closed way too early).

Here you can see different error messages depending on how long I wait before closing the tab.

Screen.Recording.42.mov

throw new BusinessError("PixieBrix doesn't have access to the tab");
}
try {
return await runBrick({ tabId }, request);
} catch (error) {
const errorMessage = getErrorMessage(error);

// Repackage tab-lifecycle-related errors as BusinessErrors
if ([errorTargetClosedEarly, errorTabDoesntExist].includes(errorMessage)) {
throw new BusinessError(errorMessage);
}

const result = await Promise.race([
// If https://github.com/pixiebrix/webext-messenger/issues/67 is resolved, we don't need the listener
onTabClose(tabId).then(() => TYPE_WAS_CLOSED),
runBrick({ tabId }, request),
]);
Comment on lines -48 to -52
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I think there was a race condition (heh) right here. If onTabClose resolved in time, we'd get "was closed". If not, we'd get the raw Chrome error because it would not be handled by this code at all.

You can see the two error message alternating here.

alternate.mov

Note

This alternating of message hasn't really been fixed by this PR.

Before

  • BusinessError: PixieBrix doesn't have access to the tab
  • BusinessError: The tab was closed
  • Error: A listener indicated an asynchronous response by returning true, but the message channel closed before a response was received

After

  • BusinessError: The target was closed before receiving a response
  • BusinessError: The tab doesn't exist

Both are "tab doesn't exist" errors but sometimes we can track why it doesn't exist, so we can throw "tab was closed" instead

// This must follow the tab existence checks or else it returns false even if the tab simply doesn't exist
if (!(await canAccessTab(tabId))) {
throw new BusinessError("PixieBrix doesn't have access to the tab");
}

if (result === TYPE_WAS_CLOSED) {
throw new BusinessError("The tab was closed");
throw error;
}

return result;
}

export async function waitForTargetByUrl(url: string): Promise<Target> {
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