Add test to check for excessive memory usage

Refs #840

Author: nene

package.json

@@ -58,6 +58,7 @@
     "fix": "yarn pretty && eslint --fix .",
     "test": "yarn grammar && jest",
     "test:watch": "yarn test -- --watch",
+    "test:perf": "yarn grammar && jest --testMatch '<rootDir>/test/perftest.ts' --coverage=false",
     "check": "yarn ts:check && yarn pretty:check && yarn lint && yarn test",
     "prepare": "yarn clean && yarn grammar && yarn fix && yarn check && yarn build",
     "pre-commit": "npm-run-all --parallel ts:changes lint:changes",

test/perftest.ts

@@ -0,0 +1,28 @@
+import { format } from '../src/sqlFormatter.js';
+
+const BASELINE = 300;
+
+describe('Performance test', () => {
+  it('uses about 300 MB of memory to format empty query', () => {
+    format('', { language: 'sql' });
+
+    expect(memoryUsageInMB()).toBeLessThan(BASELINE);
+  });
+
+  // Issue #840
+  it.skip('should use less than 100 MB of additional memory to format ~100 KB of SQL', () => {
+    // Long list of values
+    const values = Array(10000).fill('myid');
+    const sql = `SELECT ${values.join(', ')}`;
+    expect(sql.length).toBeGreaterThan(50000);
+    expect(sql.length).toBeLessThan(100000);
+
+    format(sql, { language: 'sql' });
+
+    expect(memoryUsageInMB()).toBeLessThan(BASELINE + 100);
+  });
+});
+
+function memoryUsageInMB() {
+  return Math.round(process.memoryUsage().heapUsed / 1024 / 1024);
+}