Files
rekhoff a546bc8961 Rekhoff/csharp default field values (#3235)
# Description of Changes

This is the implementation of issue #3191. This adds a Default attribute
to C# module fields.

**Note**: In C#, attribute arguments must be compile-time constants,
which means you can't directly use non-constant expressions like new
expressions, method calls, or dynamic values in attribute constructors.
(Ref:
https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/language-specification/attributes#2324-attribute-parameter-types)

For this reason, these default values are limited to primitive types,
enums, and strings.
This includes (shown as `C# Type` (`BSATN type`):

* `bool` (`Bool`)
* `sbyte` (`I8`)
* `byte` (`U8`)
* `short` (`I16`)
* `ushort` (`U16`)
* `int` (`I32`)
* `unit` (`U32`)
* `long` (`I64`)
* `ulong` (`U64`)
* `float` (`F32`)
* `double` (`F64`)
* `enum` (`Enum`)
* `string` (`String`)
* `null` (`RefOption`) <- Nullable type

Because of C# limitations, for nullable and complex data types, such as
a struct, can take use `[Default(null)]` to populate values with null
defaults. This allows things like structs to workaround the non-constant
expressions in attribute constructors limitation by allowing these
complex types to still be able to be added as new column tables.

The `int` type can also be in the form of Hex or Binary literals, such
as `[Default(0x2A)]` or `[Default(0b00101010)]`

Both Decimal (like `[Default(3.14m)]`) and Char (like `[Default('A')]`)
are unsupported types in BSATN and will still return `BSATN0001` errors.

# API and ABI breaking changes

Not API breaking.
This change only adds the `[Default(value)]` attribute logic.
Using the `[Default(value)]` attribute with older versions SpacetimeDB
C# modules will result in an error.

# Expected complexity level and risk

2

# Testing

Local testing of this requires use of CLI changes in #3278 

- [x] Regression test of functionality added.
2025-10-06 16:56:37 +00:00

20 lines
549 B
C#

using SpacetimeDB;
public static partial class Module
{
[SpacetimeDB.Table(Name = "ExampleData", Public = true)]
public partial struct ExampleData
{
[SpacetimeDB.PrimaryKey]
public uint Primary;
public uint TestPass;
}
[SpacetimeDB.Reducer]
public static void Insert(ReducerContext ctx, uint id)
{
var exampleData = ctx.Db.ExampleData.Insert(new ExampleData { Primary = id, TestPass = 1 });
Log.Info($"Inserted key {exampleData.Primary} on pass {exampleData.TestPass}");
}
}