feat: expose @slonik/pg-driver DatabaseError

.changeset/short-rats-remember.md

@@ -0,0 +1,5 @@
+---
+"@slonik/pg-driver": minor
+---
+
+expose DatabaseError

packages/pg-driver/README.md

@@ -3,4 +3,43 @@
 ```ts
 import {
   createPgDriverFactory,
-} from '@slonik/pg-driver';
+  DatabaseError,
+} from '@slonik/pg-driver';
+```
+
+## Error handling
+
+All Slonik errors extend from `SlonikError`. `SlonikError` uses `cause` property to store the original error, which might be a `DatabaseError` from `pg`. Example:
+
+```ts
+pool.on('error', (error) => {
+  const cause = error.cause;
+
+  if (cause instanceof DatabaseError) {
+    console.log(cause.code);
+  }
+});
+```
+
+This allows you to handle errors based on the lower-level error codes provided by `pg` driver.
+
+Example of handling all errors that could warrant a fatal error:
+
+```ts
+const fatalErrorClasses = [
+  // Connection Exception
+  '08',
+  // Invalid Authorization Specification
+  '28',
+];
+
+pool.on('error', (error) => {
+  if (error.cause instanceof DatabaseError) {
+    const classCode = error.cause.code.slice(0, 2);
+
+    if (fatalErrorClasses.includes(classCode)) {
+      // Initiate shutdown due to unexpected connection state.
+    }
+  }
+});
+```

packages/pg-driver/src/index.ts

@@ -1 +1,2 @@
 export { createPgDriverFactory } from './factories/createPgDriverFactory';
+export { DatabaseError } from 'pg';