Error Handling

All operations return Result<T, WebCryptoError>. The error type maps JavaScript DOMException names to typed Rust variants.

WebCryptoError

DOMException variants

Variant	JS exception	When
NotSupported(String)	NotSupportedError	Algorithm not supported by the runtime
Syntax(String)	SyntaxError	Required parameter missing or malformed
InvalidAccess(String)	InvalidAccessError	Key cannot be used for the requested operation
Data(String)	DataError	Key data is invalid
Operation(String)	OperationError	Cryptographic operation failed (e.g. decryption with wrong key)
Type(String)	TypeError	Value has the wrong type

Platform variants

Variant	When
Unknown(String)	JS error that does not match any known DOMException
NonWasmBuild	Built for a non-wasm target
RuntimeUnavailable	wasm32 build, but crypto object not found in the runtime
NotImplemented	Method not yet implemented

Usage with ?

WebCryptoError implements std::error::Error, so it works with ? and anyhow:

use anyhow::Result;

async fn hash(data: &[u8]) -> Result<String> {
    let subtle = SubtleCrypto::new()?;
    let output = subtle.digest(Hash::Sha256, data).await?;
    Ok(output.to_hex())
}