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Migrate from throwing code

You have a module — a client, a parser, a service — that throws on failure. You want it to return Result instead. Do it incrementally.

Step 1: Enable the lint rules​

Turn on the rules that flag the problem so the surface is visible:

// eslint.config.ts
import antithrow from "@antithrow/eslint-plugin";

export default [antithrow.configs.recommended];

@antithrow/no-throwing-call flags built-in throwing APIs. @antithrow/no-unused-result catches newly-returned Results that aren't handled yet.

Step 2: Wrap leaf calls first​

Start at the bottom of the call graph — any function that touches a throwing built-in. Wrap with Result.try:

// before
export function parseConfig(input: string): Config {
	return JSON.parse(input);
}

// after
import { Result } from "antithrow";

export function parseConfig(input: string): Result<Config, SyntaxError> {
	return Result.try(() => JSON.parse(input));
}

Update call sites to branch on isOk/isErr or chain with .andThen.

Step 3: Propagate upward​

Each caller either handles the error (branch) or forwards it (return the Result). Resist the urge to unwrap() to keep the old signature — that just hides the throw behind another name.

Step 4: Replace wrappers with @antithrow/* packages​

Where you wrapped fetch, JSON.parse, fs/promises, or a Standard Schema validator by hand, swap to the pre-built wrappers:

// hand-wrapped → pre-built
import { fetch } from "@antithrow/std";
import { readFile } from "@antithrow/node/fs/promises";
import { validate } from "@antithrow/standard-schema";

Step 5: Re-examine recoveries​

Once the type system shows you every error path, you will find fallbacks that were silently swallowing failures. Replace try/catch → default-value patterns with unwrapOr / orElse, explicit about what you are recovering.

See also​