[BUG] Rust wasm32-unknown-unknown build is broken with 7.15.0

[JMLX42]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

The new async file stream support for reqwest client breaks the WASM build.

• supportAsync=true (default) implies vendorExtensions.useAsyncFileStream=true, it will add tokio as a dependency with features incompatible with WASM
• supportAsync=false, it will enable the blocking feature of reqwest, which does not build for WASM

error: Only features sync,macros,io-util,rt,time are supported on wasm.
   --> /home/jmlx/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/tokio-1.47.1/src/lib.rs:475:1
    |
475 | compile_error!("Only features sync,macros,io-util,rt,time are supported on wasm.");
    |

So IMHO, essentially, the WASM build is essentially 100% broken on 7.15.0.

openapi-generator version

7.15.0

OpenAPI declaration file content or url

swagger: "2.0"
info:
  title: File Streaming Test API
  version: 1.0.0

paths:
    /upload:
      post:
        consumes:
            - application/octet-stream
        description: Upload a file from the local filesystem
        operationId: uploadFile
        parameters:
          - description: A test file
            in: body
            name: inputStream
            schema:
              format: binary
              type: string
        responses:
          '200':
            description: Success

Generation Details

java ${JAVA_OPTS} -jar ${CODEGEN} generate -i \"${INPUT_FILE}\" \
        -g ${lang} \
        -o ${TMP_PATH} \
        --additional-properties=packageName=gltf_live_client_sdk \
        --additional-properties=publishRustRegistry=false \
        --additional-properties=library=reqwest \
        --additional-properties=avoidBoxedModels=true

Steps to reproduce

1. Generate the Rust client code
2. Attempt to build for wasm32-unknown-unknown

Related issues/PRs

#21771

Suggest a fix

useAsyncFileStream should be a Cargo feature

[ThomasVille]

@wing328 @andershausding When looking at the implementation of #21771, I'm wondering why we introduced tokio instead of simply enabling and using the stream features of reqwest like it was proposed in #20242?

After enabling the stream feature we could use the Form::file method that seems to accomplish the same goal and we could just disable it on WASM:

    let mut local_var_form = reqwest::multipart::Form::new();
    #[cfg(not(target_arch = "wasm32"))]
    {
        local_var_form = local_var_form.file("file", file).await?;
    }

Am I missing something here? IMO this approach solves the issue with WASM and doesn't introduce a dependency to tokio.

[andershausding]

@wing328 @andershausding When looking at the implementation of #21771, I'm wondering why we introduced tokio instead of simply enabling and using the stream features of reqwest like it was proposed in #20242?

After enabling the stream feature we could use the Form::file method that seems to accomplish the same goal and we could just disable it on WASM:

let mut local_var_form = reqwest::multipart::Form::new();
#[cfg(not(target_arch = "wasm32"))]
{
    local_var_form = local_var_form.file("file", file).await?;
}

Am I missing something here? IMO this approach solves the issue with WASM and doesn't introduce a dependency to tokio.

This approach would load the entire file into memory, which could become an issue for big file attachments.

The idea was to not introduce more dependencies than already defined by the stream feature from reqwest, if WASM compatibility is required, i would suggest adding support for utilizing wasm-streams for WASM targets like reqwest does with feature flags as suggested by the issue creator.

Ive looked at the reqwest implementation and stand corrected, now my only issue is that this snippet is for multipart forms, whereas the stream approach is for single file bodies.

[ThomasVille]

@andershausding Thanks for the response.

I've found another issue in [Rust ]Add async file stream support for reqwest client: the useAsyncFileStream and vendorExtensions.useAsyncFileStream template variables are set as long as supportAsync is set and any parameter is a file, but I think this assumption is wrong because we can upload files in the body or in a form. So even if the only files are in forms, useAsyncFileStream will be set to true.

This likely explains why these tests have the tokio dependency even though they don't use it:

• samples/client/petstore/rust/reqwest/petstore-async-tokensource/Cargo.toml
• samples/client/petstore/rust/reqwest/petstore-async-middleware/Cargo.toml
• samples/client/petstore/rust/reqwest/petstore-async/Cargo.toml
• samples/client/petstore/rust/reqwest/petstore-avoid-box/Cargo.toml

When updating operation.allParams:

            for (var param: operation.allParams) {
                if (param.isFile && supportAsync && !useAsyncFileStream) {
                    useAsyncFileStream = true;
                    additionalProperties.put("useAsyncFileStream", Boolean.TRUE);
                    operation.vendorExtensions.put("useAsyncFileStream", Boolean.TRUE);
                    break;
                }
            }

with operation.bodyParams:

            for (var param: operation.bodyParams) {
                if (param.isFile && supportAsync && !useAsyncFileStream) {
                    useAsyncFileStream = true;
                    additionalProperties.put("useAsyncFileStream", Boolean.TRUE);
                    operation.vendorExtensions.put("useAsyncFileStream", Boolean.TRUE);
                    break;
                }
            }

the tests no longer have the unused tokio dependency.

I'll open a PR for this.

[ThomasVille]

This PR solves the issues I mentioned above.

At least now, people building for WASM and who don't upload files in the body won't have the tokio dependencies breaking the WASM build.