# 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.
# Description of Changes
Each reducer gets its arguments through an `ArgSource`, a Unix-file-like
abstraction for streams of bytes. Prior to this commit, we had an ABI
designed as if it could support other args sources, but it actually
hardcoded the ID of the reducer args source, and errored elsewhere.
This commit extends the `BytesSource` infrastructure to support other
bytes sources. This will be useful for exposing JWT payloads and HTTP
responses. No other `BytesSource` uses are actually included in this
commit, only the infrastructure.
This commit also defines a new host call,
`bytes_source_remaining_length`. This is intended to allow callers to
pre-allocate a buffer correctly sized to read the entire `BytesSource`
all at once. The new host function is added to a new ABI minor version,
10.1, so that old SpacetimeDB hosts can detect and reject too-new
compiled modules. I have added uses of this new function to
`__call_reducer__` in both Rust and C#, even though it's not strictly
necessary,
and I haven't removed the loop which repeatedly calls
`bytes_source_read` and grows the buffer.
# API and ABI breaking changes
Adds a new ABI minor version, `spacetime_10.1`. This means that old
SpacetimeDB hosts will reject new compiled modules.
# Expected complexity level and risk
2-ish? WASM ABI code is always fiddly, but this is a pretty simple case.
# Testing
- [x] New behavior and new host function are both hit through existing
tests that instantiate modules and call reducers against them, so I
believe automated testing is sufficient.
---------
Signed-off-by: Phoebe Goldman <phoebe@goldman-tribe.org>
Co-authored-by: rekhoff <r.ekhoff@clockworklabs.io>
Co-authored-by: Mazdak Farrokhzad <twingoow@gmail.com>
rekhoff