c#: Ensure imports aren't duplicated across world fragments (#1106)

Signed-off-by: James Sturtevant <jsturtevant@gmail.com>

Author: jsturtevant

crates/csharp/src/csproj.rs

@@ -71,6 +71,8 @@ impl CSProjectLLVMBuilder {
             <ImplicitUsings>enable</ImplicitUsings>
             <Nullable>enable</Nullable>
             <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+            <!-- treat these are errors so they are caught during code generation tests -->
+            <WarningsAsErrors>CS0105</WarningsAsErrors>
         </PropertyGroup>
         
         <PropertyGroup>
@@ -182,6 +184,8 @@ impl CSProjectMonoBuilder {
             <ImplicitUsings>enable</ImplicitUsings>
             <Nullable>enable</Nullable>
             <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+            <!-- treat these are errors so they are caught during code generation tests -->
+            <WarningsAsErrors>CS0105</WarningsAsErrors>
         </PropertyGroup>
         
         <PropertyGroup>

crates/csharp/src/lib.rs

@@ -647,10 +647,14 @@ impl WorldGenerator for CSharp {
                     .world_fragments
                     .iter()
                     .flat_map(|f| &f.interop_usings)
+                    .into_iter()
+                    .collect::<HashSet<&String>>() // de-dup across world_fragments
+                    .iter()
                     .map(|s| "using ".to_owned() + s + ";")
                     .collect::<Vec<String>>()
                     .join("\n"),
             );
+            src.push_str("\n");
 
             src.push_str(&format!("{access} static class {name}World\n"));
             src.push_str("{");

tests/README.md

@@ -11,7 +11,7 @@ There are a few pre-requisites to testing the project. You only need the languag
   - Rust - wasi target: `rustup target add wasm32-wasip1`
   - Java - TeaVM-WASI `ci/download-teamvm.sh`
   - C - [Clang](https://clang.llvm.org/)
-  - C# - [Dotnet 8](https://dotnet.microsoft.com/en-us/download/dotnet/8.0)
+  - C# - [Dotnet 9](https://dotnet.microsoft.com/en-us/download/dotnet/9.0)
 
 There are two suites of tests: [codegen](#testing-wit-bindgen---codegen) and [runtime](#testing-wit-bindgen---runtime).  To run all possible tests, across all supported languages, ensure the dependency above are installed then run:
 
@@ -52,6 +52,7 @@ Note that this directory can have whatever it wants since nothing implements the
 interfaces or tries to call them.
 
 It also contains git submodules for the wasi proposals like `wasi-http`.
+Use `git submodule init` +  `git submodule update` before running the tests.
 
 The tests are generated by a macro `codegen_tests` in [crates/test-helpers](../crates/test-helpers/).
 

tests/codegen/import_export_func.wit

@@ -0,0 +1,6 @@
+package foo:foo;
+
+world foo {
+  import foo: func();
+  export foo1: func();
+}