a-b-street/abstreet · error · anyhow::Error

Unsupported on web

Error message

Unsupported on web

What it means

get_clipboard is only implemented for native targets; on wasm32 the function unconditionally bails with "Unsupported on web". The browser clipboard API is not wired up in this library, so any wasm build calling this will always fail. It is a deliberate platform limitation, not a runtime fault.

Solutions

1. Gate the call with #[cfg(not(target_arch = "wasm32"))] and provide a web alternative using navigator.clipboard.readText()
2. Use cfg! or a trait to supply a platform-specific clipboard implementation
3. Disable the paste-from-clipboard UI affordance in the web build
4. Return an empty string / show a 'not supported on web' message to the user

Example fix

// before
let text = get_clipboard()?;
// after
#[cfg(target_arch = "wasm32")]
let text = String::new(); // or use wasm bindgen clipboard API
#[cfg(not(target_arch = "wasm32"))]
let text = get_clipboard()?;

let supported = cfg!(not(target_arch = "wasm32"));

fn clipboard_supported() -> bool {
    cfg!(not(target_arch = "wasm32"))
}

if cfg!(target_arch = "wasm32") {
    // use navigator.clipboard.readText() via wasm-bindgen instead
} else {
    let text = get_clipboard()?;
}

When it happens

Trigger: Calling widgetry::tools::get_clipboard() from any code compiled to wasm32 (the web build of the app).

Common situations: Shared code that pastes from clipboard runs unmodified in the browser build; feature-gating was forgotten when porting desktop functionality to web.

Understand the failure class

Background: "unsupported platform" / "not supported on this platform" errors: what they mean and how to fix them — this error's family across 47 libraries.

Related errors

• Can't slurp_file , it doesn't exist
• Can't maybe_read_binary
• Not saving
• Don't know MIME type for
• {}

AI-assisted analysis of a-b-street/abstreet@0964f29315 (2026-09-13). Data as JSON: /api/errors/a926de21c15c0db1. Report an issue: GitHub.

Appendix: source

Thrown at widgetry/src/tools/mod.rs:132

pub fn get_clipboard() -> Result<String> {
    #[cfg(not(target_arch = "wasm32"))]
    {
        use clipboard::{ClipboardContext, ClipboardProvider};
        // TODO The clipboard crate uses old nightly Errors. Converting to anyhow is weird.
        let mut ctx: ClipboardContext = match ClipboardProvider::new() {
            Ok(ctx) => ctx,
            Err(err) => bail!("{}", err),
        };
        let contents = match ctx.get_contents() {
            Ok(contents) => contents,
            Err(err) => bail!("{}", err),
        };
        Ok(contents)
    }

    #[cfg(target_arch = "wasm32")]
    {
        bail!("Unsupported on web");
    }
}

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