- fix bug where worker tries to close database twice if you sequentially apply commands "close" and "open" (#379)

Co-authored-by: kai.zhu <kai.zhu@windebt.com>

Author: kaizhu256

src/api.js

@@ -883,6 +883,10 @@ Module["onRuntimeInitialized"] = function onRuntimeInitialized() {
     * memory consumption will grow forever
      */
     Database.prototype["close"] = function close() {
+        // do nothing if db is null or already closed
+        if (this.db === null) {
+            return;
+        }
         Object.values(this.statements).forEach(function each(stmt) {
             stmt["free"]();
         });

src/worker.js

@@ -63,7 +63,12 @@ function onModuleReady(SQL) {
                 return postMessage(result);
             }
         case "close":
-            return db && db.close();
+            if (db) {
+                db.close();
+            }
+            return postMessage({
+                id: data["id"]
+            });
         default:
             throw new Error("Invalid action : " + (data && data["action"]));
     }

test/test_worker.js

@@ -91,6 +91,12 @@ exports.test = async function test(SQL, assert) {
   var actual = "";
   for (let i = 0; i < header.length; i++) actual += String.fromCharCode(data.buffer[i]);
   assert.equal(actual, header, 'Data returned is an SQLite database file');
+
+  // test worker properly opens db after closing
+  await worker.postMessage({ action: "close" });
+  await worker.postMessage({ action: "open" });
+  data = await worker.postMessage({ action: "exec", sql: "SELECT 1" });
+  assert.deepEqual(data.results, [{"columns":["1"],"values":[[1]]}]);
 }
 
 function obj2array(obj) {