Test: Exception handling in WASM component model

[dbaeumer]

Refs: microsoft/vscode-wasm#177

• anyOS @connor4312
• anyOS @hediet

Complexity: 3

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The latest implementation of VS Code's component model converts result types returned from function and methods into a normal return type (the Ok part) and an exception.

Prerequisites

1. Rust: installation instructions can be found here
2. wasm-tools: releases can be found here. You need at least version >= 1.200 to run the example.

Testplan

You can make your own component model sample using the two blog posts as a starter: https://code.visualstudio.com/blogs/2024/05/08/wasm and https://code.visualstudio.com/blogs/2024/06/07/wasm-part2

Easier is to clone the vscode-extension-samples and start off the wasm-component-model sample

• run npm install

• add an error-code enumeration to the calculator.wit file inside the types interface. Something like this:

	enum error-code {
		none,
		overflow,
		divide-by-zero
	}

• use error-code inside the calculator world and change the signature of the calc function to return result<u32, error-code>. The world will look like this:

world calculator {
	use types.{ operation, error-code };
	import log: func(msg: string);

	export calc: func(o: operation) -> result<u32, error-code>;
}

• run npm run generate:model
• observe: a new calculator.ts file got created with as an ErrorCode enumeration and a corresponding exception.
• adapt the Rust code in lib.rs to return Result::Err(ErrorCode::DivideByZero) in case a division by Zero happens.
• adapt the TypeScript code in extension.ts to catch error when calling a Div operation. Ensure that the return exception if of type Types.ErrorCode.Error_ and its value is error.value === Types.ErrorCode.divideByZero. Something like

		try {
			const div = Types.Operation.Div({ left: 10, right: 0 });
			channel.appendLine(`Div ${api.calc(div)}`);
		} catch (error) {
			if (error instanceof Types.ErrorCode.Error_ && error.value === Types.ErrorCode.divideByZero) {
				channel.appendLine('Division by zero not allowed');
			}
		}

[hediet]

Nice work!