[Demo] Local-only supabase todo app

demos/django-todolist/pubspec.lock

@@ -439,10 +439,10 @@ packages:
     dependency: "direct main"
     description:
       name: sqlite_async
-      sha256: "79e636c857ed43f6cd5e5be72b36967a29f785daa63ff5b078bd34f74f44cb54"
+      sha256: "7708a2129582d43614f436e28623fcbeb142a02022ba372e45cfe403c84dd2b5"
       url: "https://pub.dev"
     source: hosted
-    version: "0.8.1"
+    version: "0.8.3"
   stack_trace:
     dependency: transitive
     description:

demos/django-todolist/pubspec.yaml

@@ -14,7 +14,7 @@ dependencies:
   path_provider: ^2.1.1
   path: ^1.8.3
   logging: ^1.2.0
-  sqlite_async: ^0.8.1
+  sqlite_async: ^0.8.3
   http: ^1.2.1
   shared_preferences: ^2.2.3
 

demos/local-only-todolist/.gitignore

@@ -0,0 +1,47 @@
+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.buildlog/
+.history
+.svn/
+migrate_working_dir/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+**/doc/api/
+**/ios/Flutter/.last_build_id
+.dart_tool/
+.flutter-plugins
+.flutter-plugins-dependencies
+.packages
+.pub-cache/
+.pub/
+/build/
+
+# Symbolication related
+app.*.symbols
+
+# Obfuscation related
+app.*.map.json
+
+# Android Studio will place build artifacts here
+/android/app/debug
+/android/app/profile
+/android/app/release
+
+# asdf
+.tool-versions

demos/local-only-todolist/.metadata

@@ -0,0 +1,30 @@
+# This file tracks properties of this Flutter project.
+# Used by Flutter tool to assess capabilities and perform upgrades etc.
+#
+# This file should be version controlled and should not be manually edited.
+
+version:
+  revision: "5dcb86f68f239346676ceb1ed1ea385bd215fba1"
+  channel: "stable"
+
+project_type: app
+
+# Tracks metadata for the flutter migrate command
+migration:
+  platforms:
+    - platform: root
+      create_revision: 5dcb86f68f239346676ceb1ed1ea385bd215fba1
+      base_revision: 5dcb86f68f239346676ceb1ed1ea385bd215fba1
+    - platform: web
+      create_revision: 5dcb86f68f239346676ceb1ed1ea385bd215fba1
+      base_revision: 5dcb86f68f239346676ceb1ed1ea385bd215fba1
+
+  # User provided section
+
+  # List of Local paths (relative to this file) that should be
+  # ignored by the migrate tool.
+  #
+  # Files that are not part of the templates will be ignored by default.
+  unmanaged_files:
+    - 'lib/main.dart'
+    - 'ios/Runner.xcodeproj/project.pbxproj'

demos/local-only-todolist/LICENSE

@@ -0,0 +1,121 @@
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demos/local-only-todolist/README.md

@@ -0,0 +1,106 @@
+# PowerSync + Supabase Flutter Todo List App: Local-Only to Sync Mode Demo
+
+This demo app is an extension of the [Supabase Todo List App](../supabase-todolist/README.md) and demonstrates using the PowerSync Flutter client SDK to persist data locally without syncing, for users to use the app without having to register or sign in. It then demonstrates syncing this data to Supabase once the user registers at a later stage.
+
+The recommended flow through this demo is:
+1. Run the app in local-only mode and create data. Notice how data persists even when closing and reopening the app.
+2. Enable user registration and sign in to the app.
+3. Notice how previously created data now seamlessly syncs with Supabase.
+
+For an overview of the mechanics behind this, see [the explanation further below](#how-this-works).
+
+# Run the app in local-only mode
+
+Ensure you have [melos](https://melos.invertase.dev/~melos-latest/getting-started) installed.
+
+1. `cd demos/local-only-todolist`
+2. `melos prepare`
+3. `flutter run`
+
+Create some data and notice how the data persists after a refresh or reopening the app.
+
+It is expected that users cannot register or sign in at this stage. This is because Supabase and PowerSync credentials have not been been configured yet -- there is a hardcoded check in `main.dart` for this. We'll get to this next.
+
+# Enable user registration and sign in
+
+Create Supabase and PowerSync projects, and add their credentials to `lib/app_config.dart` to enable user registration and sign in.
+
+## Set up your Supabase project
+
+Detailed instructions for integrating PowerSync with Supabase can be found in [the integration guide](https://docs.powersync.com/integration-guides/supabase). Below are the main steps required to get this demo running.
+
+Create a new Supabase project, and paste an run the contents of [database.sql](./database.sql) in the Supabase SQL editor.
+
+It does the following:
+
+1. Create `lists` and `todos` tables.
+2. Create a publication called `powersync` for `lists` and `todos`.
+3. Enable row level security, allowing users to only view and edit their own data.
+4. Create a trigger to populate some sample data when an user registers.
+
+## Configure your PowerSync Instance
+
+Create a new PowerSync instance, connecting to the database of the Supabase project. See instructions [here](https://docs.powersync.com/integration-guides/supabase-+-powersync#connect-powersync-to-your-supabase).
+
+Then deploy the following sync rules:
+
+```yaml
+bucket_definitions:
+  user_lists:
+    # Separate bucket per todo list
+    parameters: select id as list_id from lists where owner_id = request.user_id()
+    data:
+      - select * from lists where id = bucket.list_id
+      - select * from todos where list_id = bucket.list_id
+```
+
+## Configure the app
+
+Insert the credentials of your Supabase and PowerSync projects into `lib/app_config.dart`.
+
+## Sign in to the app
+
+Restart the app and sign up or sign in. Once successfully signed in, existing and new data should seamlessly sync with Supabase.
+
+
+# How this works
+
+This app uses [local-only](https://pub.dev/documentation/powersync/latest/powersync/Table/Table.localOnly.html) tables to persist data until the user has registered or signed in. Local-only tables do not log updates in an upload queue, avoiding any overhead or growth in database size.
+
+Once the user registers, the data is moved over to synced tables, at which point the data would be placed in the upload queue and will start syncing.
+
+## Naive implementation
+
+A barebones way to achieve the above is to store and query data from local-only tables before registration, copy this data to each corresponding synced table after registration and then store and query from the synced tables. This would look as follows:
+
+![diagram-0](./assets/local-only-readme-0.png)
+
+The downside to this approach is that app queries would need to continuously differentiate between the two tables based on whether the user signed in or not.
+
+## Recommended implementation
+
+To keep app queries consistent between the two states, we utilize the [viewName](https://pub.dev/documentation/powersync/latest/powersync/Table/viewName.html) property, which allows overriding the default name of schema views (each table automatically has a corresponding view, defaulting to the table name, which is used in queries). 
+
+This looks as follows in the local-only state:
+
+![diagram-1](./assets/local-only-readme-1.png)
+
+The local-only tables (`local_lists` and `local_todos`) have their view names overriden to `lists` and `todos`, and these names are used in queries (e.g. `PowerSync.getAll("SELECT * FROM lists");`). The `lists` and `todos` tables, which are the sync-enabled tables without the `localOnly` flag, are not used at this stage, as indicated by their `inactive_synced_` view names.
+
+When the user registers / signs in:
+
+![diagram-2](./assets/local-only-readme-2.png)
+
+The _synced_ tables (`lists` and `todos`) now have their view names set to `lists` and `todos`. Note that `updateSchema` must be run to update the view name. See the [schema](./lib/models/schema.dart) for details about this. The app query `PowerSync.getAll("SELECT * FROM lists")` now reads data from the `lists` table. 
+
+Finally, copy data from the local-only tables to the synced tables, and delete data from the local-only tables to reduce database size:
+
+![diagram-3](./assets/local-only-readme-3.png)
+
+At this point, being signed in no longer determines which schema should be used, as the user's session expiring and explicitly signing out trigger different behaviors. If the session expires, the user can continue interacting with their data. However, if the user explicitly logs out, all data is cleared, effectively resetting the app. To manage this, an additional local storage mechanism is used to track which schema is currently in use, as seen [here](./lib/models/sync_mode.dart). Note that any other local storage solution would work as long as it's not using the PowerSync database (chicken and egg problem).
+
+
+# Limitations
+
+- `updateSchema` cannot be called inside a transaction, and it's recommended to perform the schema update when the database isn't connected.
+- Additionally, the current implementation of the PowerSync SDK's `watch` method may not correctly track tables that are altered by `updateSchema`. Note that `refreshSchema` can be executed after updating the schema to resolve this (the demo uses it in `switchToSyncedSchema` which can be viewed [here](./lib/models/schema.dart)).

demos/local-only-todolist/analysis_options.yaml

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+# This file configures the analyzer, which statically analyzes Dart code to
+# check for errors, warnings, and lints.
+#
+# The issues identified by the analyzer are surfaced in the UI of Dart-enabled
+# IDEs (https://dart.dev/tools#ides-and-editors). The analyzer can also be
+# invoked from the command line by running `flutter analyze`.
+
+# The following line activates a set of recommended lints for Flutter apps,
+# packages, and plugins designed to encourage good coding practices.
+include: package:flutter_lints/flutter.yaml
+
+linter:
+  # The lint rules applied to this project can be customized in the
+  # section below to disable rules from the `package:flutter_lints/flutter.yaml`
+  # included above or to enable additional rules. A list of all available lints
+  # and their documentation is published at
+  # https://dart-lang.github.io/linter/lints/index.html.
+  #
+  # Instead of disabling a lint rule for the entire project in the
+  # section below, it can also be suppressed for a single line of code
+  # or a specific dart file by using the `// ignore: name_of_lint` and
+  # `// ignore_for_file: name_of_lint` syntax on the line or in the file
+  # producing the lint.
+  rules:
+    # avoid_print: false  # Uncomment to disable the `avoid_print` rule
+    # prefer_single_quotes: true  # Uncomment to enable the `prefer_single_quotes` rule
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options

demos/local-only-todolist/android/.gitignore

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+gradle-wrapper.jar
+/.gradle
+/captures/
+/gradlew
+/gradlew.bat
+/local.properties
+GeneratedPluginRegistrant.java
+
+# Remember to never publicly share your keystore.
+# See https://flutter.dev/docs/deployment/android#reference-the-keystore-from-the-app
+key.properties
+**/*.keystore
+**/*.jks