[Feature] Class-based schema definition

[LucDeCaf]

Discussion: #34

TODO:

• Schema.WithOptions or similar - basically some mechanism for overriding options on schema creation
• AttributeParser tests
• Refactor other demos
• Refactor tests

Class based schema definition

Provides a new syntax for defining the PowerSync schema using C# classes and attributes.

Example

using PowerSync.Common.DB.Schema;
using PowerSync.Common.DB.Schema.Attributes;

[
    Table("todos"),
    Index("list", ["list_id"]),
    Index("created_at", ["created_at"])
]
public class Todo
{
    [Column("id")]
    public string TodoId { get; set; }

    [Column("list_id")]
    public string ListId { get; set; }

    [Column("created_at")]
    public DateTime CreatedAt { get; set; }

    [Column("completed_at")]
    public DateTime? CompletedAt { get; set; }

    [Column("created_by")]
    public string CreatedBy { get; set; }

    [Column("completed_by")]
    public string? CompletedBy { get; set; }

    [Column("completed")]
    public bool Completed { get; set; }
}

[Table("lists")]
public class List
{
    [Column("id")]
    public string ListId { get; set; }

    [Column("created_at")]
    public string CreatedAt { get; set; }

    [Column("name")]
    public string Name { get; set; }

    [Column("owner_id")]
    public string OwnerId { get; set; }
}

public class AppSchema
{
    public static Schema PowerSyncSchema = new Schema(typeof(Todo), typeof(List));
}

// Usage
var list = db.Get<List>("SELECT * FROM lists WHERE owner_id = ? ORDER BY created_at LIMIT 1", [userId]);
var todos = db.GetAll<Todo>("SELECT * FROM todos WHERE list_id = ?", [list.ListId]);

This syntax allows you to define both a result type for queries and the PowerSync schema definitions from the same language construct.

Setting options

Options are set primarily in the Table attribute. Indexes are defined via the Index attribute, which can be defined multiple times for the same table. Column-specific settings (i.e. column aliases, ColumnType, and TrackPrevious) can be customised via the Column attribute. Properties can be excluded from defining SQLite columns via the Ignored attribute.

[
    Table(
        "logs",
        LocalOnly = true,
        InsertOnly = false,
        ViewName = "logs_local",
        TrackMetadata = false,
        IgnoreEmptyUpdates = true,
        // `TrackPreviousValues` is set via the `TrackPrevious` enum, since attributes can't accept arbitrary class instances.
        TrackPrevious = TrackPrevious.Columns | TrackPrevious.OnlyWhenChanged
    ),
    Index("created_at", ["created_at"])
]
public class Log
{
    // Change the name of the backing SQLite column
    [Column("id")]
    public string LogId { get; set; }

    // Manually set the column type (default is ColumnType.Inferred)
    [Column(ColumnType = ColumnType.Text)]
    public DateTime created_at { get; set; }

    // Track changes on this column
    [Column(TrackPrevious = true)]
    public string description { get; set; }

    // Combine multiple options
    [Column("log_level", ColumnType = ColumnType.Integer, TrackPrevious = true)]
    public int LogLevel { get; set; }

    // Exclude properties from creating SQLite columns
    [Ignored]
    public string LogLevelString { get { return LogLevel.ToString(); } }
}

The Table object also contains a number of ways to manually set the table options.

public static Table TodosTable = new Table(typeof(Todo));

// Create a new table from an existing Table object
Table TodosWithOptions = new Table(TodosTable, new TableOptions(/* ... */));

// OR: Create a new table from a [Table] class
Table TodosWithOptions = new Table(typeof(Todo), new TableOptions(/* ... */));

// OR: Set Table.Options directly
Table TodosWithOptions = new Table(typeof(Todo));
TodosWithOptions.Options = new TableOptions(/* ... */);

// OR: Use the old syntax for creating tables
Table TodosWithOptions = new Table("todos", columns: new Dictionary(/* ... */), options: new TableOptions(/* ... */));

[LucDeCaf]

This looks like this because part of the formatting converted CRLF in some of the demos to LF

[LucDeCaf]

Same reason as above for why the diff looks so bad