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AutistMask/src/background/state.js
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fix: AutistMask does not work in Firefox private windows (closes #646)
Firefox gives an extension page in a private window locks of its own, so a popup there could save between the background's read and its write and undo a network switch the background saved. `manifest/firefox.json` now sets `"incognito": "not_allowed"`, so such a page cannot read or write extension storage, and `tests/manifest.test.js` pins the key. README and the user guide say AutistMask does not work in Firefox private windows. Chrome needs no change: in its default incognito mode an extension page shares the background's lock.

A Firefox user on "Never remember history" can no longer run AutistMask at all.

Model: opus-5-5
2026-10-26 23:51:22 +01:00

88 lines
4.4 KiB
JavaScript

// The background's access to the persisted profile.
//
// There is no in-memory copy here, and that is the whole design. The MV3
// service worker is terminated when idle and revived by the next message, so
// anything held at module scope is either absent or arbitrarily stale, and
// src/shared/state.js's module-level `state` singleton — which nothing in the
// worker ever populates — silently served DEFAULT_STATE to whoever read it.
// Five defects came out of that (https://git.eeqj.de/sneak/AutistMask/issues/324),
// and every point fix for one of them added a loadState() that created the
// next: loading detaches the objects an in-flight handler is holding.
//
// So the background reads per call and writes read-modify-write:
//
// getState() one storage read, normalized, detached. Nothing else
// holds the object it returns, so a handler may keep it
// across any number of awaits and no concurrent work can
// move it.
// updateState(fn) read fresh, apply fn to that fresh record, write it
// back — all holding the lock every write of the stored
// record takes, so no other write lands in between, by
// the background or by any page (README, "Stored state
// and its version"). The read is one storage round trip
// ahead of the write rather than a page lifetime ahead of
// it (which is what made the popup's saveState() need a
// per-field merge against a baseline at all).
//
// A handler that must both read and write therefore does its network work
// against a snapshot it owns, and applies the RESULT inside updateState().
// It never publishes an object other in-flight work is holding.
const { storageGet, storageSet, withLock } = require("../shared/browserApi");
const { normalizePersisted } = require("../shared/persistedState");
const {
STATE_SCHEMA_VERSION,
assertStateUsable,
} = require("../shared/stateSchema");
// A fresh, fully-normalized, detached copy of the persisted profile.
//
// Normalized rather than raw: a legacy or malformed record is self-healed the
// same way loadState() heals it for the popup, so the background is never the
// one context reasoning about a shape the rest of the extension repairs.
//
// Throws StateUnusableError for a record this build cannot make sense of,
// before normalization gets a chance to paper over it — the same gate, in the
// same place, as the popup's loadState(). Every handler that consults the
// profile comes through here, so a dApp call against such a record is answered
// with the specific error the dispatcher maps that to (src/background/index.js)
// rather than dereferencing its way into a generic -32603.
async function getState() {
const result = await storageGet("autistmask");
assertStateUsable(result.autistmask);
return normalizePersisted(result.autistmask);
}
async function updateStateOnce(mutate) {
const s = await getState();
await mutate(s);
s.hasWallet = Boolean(s.wallets && s.wallets.length > 0);
// Stamped on every write, exactly as the popup's saveState() stamps it:
// whichever context writes last, the record in storage is in this build's
// shape and says so.
s.schemaVersion = STATE_SCHEMA_VERSION;
await storageSet({ autistmask: s });
return s;
}
// Apply `mutate` to a record read fresh from storage and write the result
// back. `mutate` receives a detached, normalized profile and mutates it in
// place; it may be async, but it must not do anything slow. The write is the
// WHOLE record, which is safe only because the lock (withLock() in
// src/shared/browserApi.js) is held from the read to the write: two
// background turns, or a turn and a page's save, never interleave
// (https://git.eeqj.de/sneak/AutistMask/issues/641). Every page's save waits
// while it is held (README, "Stored state and its version").
//
// `mutate` must also not call updateState() itself, directly or through
// anything it awaits: the inner turn waits for the lock the outer one holds,
// and the outer one is waiting on the inner one. That deadlocks every write of
// the stored record, not just the caller. Mutate the record you were handed.
//
// Resolves with the record that was written.
function updateState(mutate) {
return withLock("autistmask", () => updateStateOnce(mutate));
}
module.exports = { getState, updateState };