unsafe: add test case which covers inserting data while iterating over the same table

Author: missinglink

test/44.unsafe.mode.js

@@ -0,0 +1,50 @@
+'use strict'
+const Database = require('../.');
+
+// writing to a table while reading the same table within an iterator.
+function writeWhileIterating(db) {
+  // create table & prepared statements
+  db.prepare(`CREATE TABLE test (a TEXT)`).run();
+  const stmt = {
+    insert: db.prepare(`INSERT INTO test VALUES (?)`),
+    each: db.prepare(`SELECT * FROM test WHERE a == 'FOO'`)
+  };
+
+  // populate table with two FOO values
+  stmt.insert.run('FOO');
+  stmt.insert.run('FOO');
+
+  // iterate and insert from/to the same table at the same time
+  // note: we insert 'BAR' which is not matched by the iterator.
+  // warning: this is unsafe, if you insert 'FOO' here then the
+  // database connection will hang forever, you were warned!
+  for (let _ of stmt.each.iterate()) {
+    stmt.insert.run('BAR');
+  }
+};
+
+describe('unsafe mode', () => {
+  afterEach(() => {
+    if (this.db) this.db.close();
+  });
+
+  it('disabled: writeWhileIterating', () => {
+    this.db = new Database(util.next(), { unsafe: false });
+    expect(this.db.unsafe).to.be.false;
+    expect(() => {
+      writeWhileIterating(this.db);
+    }).to.throw(TypeError);
+  });
+  it('enabled: writeWhileIterating', () => {
+    this.db = new Database(util.next(), { unsafe: true });
+    expect(this.db.unsafe).to.be.true;
+    expect(() => {
+      writeWhileIterating(this.db);
+    }).not.throw();
+    const aggs = this.db.prepare(`SELECT a, COUNT(a) AS total FROM test GROUP BY a`).all();
+    expect(aggs).to.eql([
+      { a: 'BAR', total: 2 }, // two 'BAR' rows
+      { a: 'FOO', total: 2 }  // two 'FOO' rows
+    ]);
+  });
+});