Fix full-text indexing failing silently after periodic vacuum or backup

vacuum() and the APFS-cloning offline backup path both close and
reopen the SQLite connection, which drops all ATTACHed databases --
including the in-memory "indexing" alias used for the fulltextWords
scratch table set up in Fulltext.init(). Once the connection is
reopened, indexing queries fail with "no such table:
indexing.fulltextWords", and indexItems()'s ignoreErrors path
routes the error to logError(), so indexing silently stops working
for the rest of the session.

Add an onConnect() hook on Zotero.DBConnection for per-connection
state that doesn't persist across reopens, and use it from
Fulltext.init() to re-attach the indexing DB on each reconnect.

Regression sources:

- 67288047f3 ("Use APFS cloning for file copies on macOS") flips
  online idle backups to offline-with-clone on APFS, so every idle
  backup interval (24h default) closes and reopens the connection.
  Affects Mac users on APFS.
- b27c4cb023 ("Enable SQLite WAL mode and add periodic VACUUM
  INTO") adds the vacuum path, which closes and reopens on the
  first idle period in a session that passes the freelist/time
  gates. Affects all users with sufficient DB churn, roughly once
  per 14 days.

https://forums.zotero.org/discussion/131576/debug-id-d848621212-indexing-of-pdfs-fail-zotero-9-0-3
https://forums.zotero.org/discussion/131718/possible-bug-regression-report-search-unusable-on-macos-zotero-9-0-3-with-large-library
(cherry picked from commit 70c4cadab1)

chrome/content/zotero/xpcom/db.js

@@ -105,7 +105,8 @@ Zotero.DBConnection = function (dbNameOrPath) {
 	};
 	this._dbIsCorrupt = null
 	this._onlineBackupInProgress = false;
-	
+	this._onConnectCallbacks = [];
+
 	this._transactionPromise = null;
 	
 	if (dbNameOrPath == 'zotero') {
@@ -987,6 +988,21 @@ Zotero.DBConnection.prototype.closeDatabase = async function (permanent) {
 };
 
 
+/**
+ * Register a callback to run after the SQLite connection is opened, including after it has
+ * been closed and reopened (e.g., after vacuum()). Use this for per-connection state that
+ * doesn't persist across reopens, such as ATTACHed databases or temp tables.
+ *
+ * The callback is not invoked for the connection that's already open at registration time --
+ * the caller is responsible for any initial setup.
+ *
+ * @param {Function} callback - Async function called with no arguments after each (re)open
+ */
+Zotero.DBConnection.prototype.onConnect = function (callback) {
+	this._onConnectCallbacks.push(callback);
+};
+
+
 /**
  * @deprecated
  */
@@ -1302,7 +1318,16 @@ Zotero.DBConnection.prototype._getConnectionAsync = async function () {
 			idleService.addIdleObserver(this, 300);
 		});
 	}
-	
+
+	for (let callback of this._onConnectCallbacks) {
+		try {
+			await callback();
+		}
+		catch (e) {
+			Zotero.logError(e);
+		}
+	}
+
 	return this._connection;
 };
 

chrome/content/zotero/xpcom/fulltext.js

@@ -61,9 +61,15 @@ Zotero.Fulltext = Zotero.FullText = new function () {
 	var _syncLibraryVersion = 0;
 	
 	this.init = async function () {
-		await Zotero.DB.queryAsync("ATTACH ':memory:' AS 'indexing'");
-		await Zotero.DB.queryAsync('CREATE TABLE indexing.fulltextWords (word NOT NULL)');
-		
+		let setUpIndexingDB = async () => {
+			await Zotero.DB.queryAsync("ATTACH ':memory:' AS 'indexing'");
+			await Zotero.DB.queryAsync('CREATE TABLE indexing.fulltextWords (word NOT NULL)');
+		};
+		await setUpIndexingDB();
+		// ATTACHed databases don't survive a connection reopen (e.g., after vacuum), so
+		// re-run the setup on every reconnect
+		Zotero.DB.onConnect(setUpIndexingDB);
+
 		let pdfConverterFileName = "pdftotext";
 		let pdfInfoFileName = "pdfinfo";
 		

test/tests/dbTest.js

@@ -453,4 +453,16 @@ describe("Zotero.DB", function () {
 			assert.isTrue(await IOUtils.exists(bakFile));
 		});
 	});
+
+	describe("#onConnect()", function () {
+		it("should run registered callbacks after the connection is reopened", async function () {
+			let count = 0;
+			Zotero.DB.onConnect(async () => {
+				count++;
+			});
+			await Zotero.DB.closeDatabase();
+			await Zotero.DB.valueQueryAsync("SELECT 1");
+			assert.equal(count, 1);
+		});
+	});
 });

test/tests/fulltextTest.js

@@ -62,6 +62,16 @@ describe("Zotero.FullText", function () {
 				);
 			});
 
+			it("should still work after the DB connection is reopened", async function () {
+				var item = await importFileAttachment('test.txt');
+				await Zotero.DB.vacuum({ force: true });
+				await Zotero.Fulltext.indexItems([item.id]);
+				assert.equal(
+					((await Zotero.Fulltext.getIndexedState(item))),
+					Zotero.Fulltext.INDEX_STATE_INDEXED
+				);
+			});
+
 			describe("Indexing with HiddenBrowser", () => {
 				it("should index attachment as its attachmentContentType when supported", async function () {
 					// Firefox would normally load this as text/x-shellscript, but we detect text/plain