Fix importing and exporting docs for drift_flutter

Closes simolus3#3498

Author: simolus3

docs/docs/Examples/existing_databases.md

@@ -38,8 +38,6 @@ flutter:
 
 To initialize the database before using drift, you need to extract the asset from your
 app onto the device.
-In drift, you can use a [LazyDatabase](https://pub.dev/documentation/drift/latest/drift/LazyDatabase-class.html)
-to perform that work just before your drift database is opened:
 
 ```dart
 import 'package:drift/drift.dart';
@@ -79,6 +77,21 @@ LazyDatabase _openConnection() {
 }
 ```
 
+===  "Using `drift_flutter`"
+
+    {{ load_snippet('(full)','lib/snippets/examples/existing_databases_flutter.dart.excerpt.json',indent=4) }}
+
+===  "Using `package:drift/native.dart`"
+
+    In drift, you can use a [LazyDatabase](https://pub.dev/documentation/drift/latest/drift/LazyDatabase-class.html)
+    to perform that work just before your drift database is opened:
+
+    {{ load_snippet('(full)','lib/snippets/examples/existing_databases_native.dart.excerpt.json',indent=4) }}
+
+
+!!! warning
+    This snippet only works on native platforms. See [existing databases on the web](../Platforms/web.md#using-existing-databases) for web support.
+
 Finally, use that method to open your database:
 
 ```dart

docs/lib/snippets/examples/existing_databases_flutter.dart

@@ -0,0 +1,35 @@
+import 'dart:io';
+
+import 'package:drift/drift.dart';
+
+import 'package:drift_flutter/drift_flutter.dart';
+import 'package:flutter/services.dart' show rootBundle;
+import 'package:path/path.dart' as p;
+import 'package:path_provider/path_provider.dart';
+
+QueryExecutor openConnection() {
+  return driftDatabase(
+    // By default, drift creates a file named app.sqlite based on the name here.
+    // Because we need to interact with the underlying file, we add the
+    // `databasePath` option to specify the exact path here.
+    name: 'app',
+    native: DriftNativeOptions(
+      databasePath: () async {
+        // put the database file, called db.sqlite here, into the documents
+        // folder for your app.
+        final dbFolder = await getApplicationDocumentsDirectory();
+        final file = File(p.join(dbFolder.path, 'app.db'));
+
+        if (!await file.exists()) {
+          // Extract the pre-populated database file from assets
+          final blob = await rootBundle.load('assets/my_database.db');
+          final buffer = blob.buffer;
+          await file.writeAsBytes(
+              buffer.asUint8List(blob.offsetInBytes, blob.lengthInBytes));
+        }
+
+        return file.path;
+      },
+    ),
+  );
+}

docs/lib/snippets/examples/existing_databases_native.dart

@@ -0,0 +1,40 @@
+import 'dart:io';
+
+import 'package:drift/drift.dart';
+import 'package:drift/native.dart';
+import 'package:flutter/services.dart' show rootBundle;
+import 'package:path/path.dart' as p;
+import 'package:path_provider/path_provider.dart';
+import 'package:sqlite3/sqlite3.dart';
+import 'package:sqlite3_flutter_libs/sqlite3_flutter_libs.dart';
+
+QueryExecutor openConnection() {
+  return LazyDatabase(() async {
+    // put the database file, called db.sqlite here, into the documents folder
+    // for your app.
+    final dbFolder = await getApplicationDocumentsDirectory();
+    final file = File(p.join(dbFolder.path, 'app.db'));
+
+    if (!await file.exists()) {
+      // Extract the pre-populated database file from assets
+      final blob = await rootBundle.load('assets/my_database.db');
+      final buffer = blob.buffer;
+      await file.writeAsBytes(
+          buffer.asUint8List(blob.offsetInBytes, blob.lengthInBytes));
+    }
+
+    // Also work around limitations on old Android versions
+    if (Platform.isAndroid) {
+      await applyWorkaroundToOpenSqlite3OnOldAndroidVersions();
+    }
+
+    // Make sqlite3 pick a more suitable location for temporary files - the
+    // one from the system may be inaccessible due to sandboxing.
+    final cachebase = (await getTemporaryDirectory()).path;
+    // We can't access /tmp on Android, which sqlite3 would try by default.
+    // Explicitly tell it about the correct temporary directory.
+    sqlite3.tempDirectory = cachebase;
+
+    return NativeDatabase.createInBackground(file);
+  });
+}

docs/pubspec.yaml

@@ -45,7 +45,7 @@ dev_dependencies:
   webdev: ^3.6.0
   code_snippets:
     hosted: https://pub-simonbinder-eu.fsn1.your-objectstorage.com
-    version: ^0.0.16
+    version: ^0.0.18
   sass_builder: ^2.2.1
 
 dependency_overrides: