document testing

Additionally, remove unnecessary "--invoke _start" from the CI

Author: wmitros

.github/workflows/rust.yml

@@ -36,7 +36,7 @@ jobs:
         set -o pipefail
         curl https://wasmtime.dev/install.sh -sSf | bash
     - name: Test
-      run: CARGO_TARGET_WASM32_WASI_RUNNER="/home/runner/.wasmtime/bin/wasmtime --invoke _start --allow-unknown-exports" cargo test --target=wasm32-wasi --all-targets
+      run: CARGO_TARGET_WASM32_WASI_RUNNER="/home/runner/.wasmtime/bin/wasmtime --allow-unknown-exports" cargo test --target=wasm32-wasi --all-targets
 
   # Tests that our current minimum supported rust version compiles everything sucessfully
   min_rust:

README.md

@@ -103,3 +103,16 @@ If CQL types `T1`, `T2`, ... map to Rust types `RustT1`, `RustT2`, ..., you can
 
 If a CQL Value of type T, that's mapped to type RustT, may be a null (possible in non-`RETURNS NULL ON NULL INPUT` UDFs),
 the type used in the Rust function should be Option\<RustT\>.
+
+## Contributing
+
+In general, try to follow the same rules as in https://github.com/scylladb/scylla-rust-driver/blob/main/CONTRIBUTING.md
+
+### Testing
+
+This crate is meant to be compiled to a `wasm32-wasi` target and ran in a WASM runtime. The tests that use WASM-specific code will most likely not succeed when executed in a different way (in particular, with a simple `cargo test` command).
+
+For example, if you have the [wasmtime](https://docs.wasmtime.dev/cli-install.html) runtime installed and in `PATH`, you can use the following command to run tests:
+```text
+CARGO_TARGET_WASM32_WASI_RUNNER="wasmtime --allow-unknown-exports" cargo test --target=wasm32-wasi
+```

scylla-udf-macros/src/export_udf.rs

@@ -74,14 +74,14 @@ fn get_exported_fun(
 }
 
 /// The macro transforms a function:
-/// ```
+/// ```compile_fail
 /// #[scylla_udf::export_udf]
 /// fn foo(arg1: u32, arg2: String) -> u32 {
 ///     arg1 + arg2.len() as u32
 /// }
 /// ```
 /// into something like:
-/// ```
+/// ```compile_fail
 /// fn foo(arg1: u32, arg2: String) -> u32 {
 ///     arg1 + arg2.len() as u32
 /// }