An ESLint plugin enforcing proper handling of neverthrow Result values.
npm install eslint-plugin-neverthrow-must-useAn ESLint plugin enforcing proper handling of neverthrow Result values.
You are forced to consume the result in one of the following three ways:
* Calling .match
* Calling .unwrapOr
* Calling ._unsafeUnwrap
Install the plugin and required dependencies:
``sh`
npm install neverthrow
npm install --save-dev eslint-plugin-neverthrow-must-use eslint @typescript-eslint/parser @typescript-eslint/eslint-plugin typescript
---
`js
import neverthrowMustUse from "eslint-plugin-neverthrow-must-use"; // Import plugin
import tsPlugin from "@typescript-eslint/eslint-plugin"; // Import TypeScript plugin
import tsParser from "@typescript-eslint/parser"; // Import TypeScript parser
export default [
{
files: ["src//.ts", "src//.tsx"], // Apply to TypeScript files
languageOptions: {
parser: tsParser, // Set TypeScript parser
parserOptions: {
ecmaVersion: "latest",
sourceType: "module",
project: "./tsconfig.json", // Ensure ESLint reads tsconfig
tsconfigRootDir: process.cwd(),
},
},
plugins: {
"@typescript-eslint": tsPlugin, // Enable TypeScript ESLint rules
"neverthrow-must-use": neverthrowMustUse, // Register the plugin
},
rules: {
"@typescript-eslint/no-unused-vars": "error", // Example TypeScript rule
"neverthrow-must-use/must-use-result": "error", // Enforce neverthrow rule`
},
},
];
---
`json`
{
"compilerOptions": {
"target": "ES2022",
"module": "ESNext",
"moduleResolution": "Node",
"strict": true,
"esModuleInterop": true,
"skipLibCheck": true,
"forceConsistentCasingInFileNames": true
},
"include": ["src"]
}
ts
import { ok, err, Result } from "neverthrow";function divide(a: number, b: number): Result {
return b === 0 ? err(new Error("Cannot divide by zero")) : ok(a / b);
}
function main() {
const result = divide(10, 2);
result.map((value) => {
console.log(value); // ❌ ESLint will throw an error
});
}
`$3
ts
import { ok, err, Result } from "neverthrow";function divide(a: number, b: number): Result {
return b === 0 ? err(new Error("Cannot divide by zero")) : ok(a / b);
}
function main() {
const result = divide(10, 2);
result.match({
ok: (value) => console.log(value),
err: (error) => console.error(error),
}); // ✅ Proper handling
}
`---
🛠 Troubleshooting
$3
Run:
sh
npx eslint --debug
`
You should see output showing that is loaded.$3
Check that the plugin is installed:
`sh
npm ls eslint-plugin-neverthrow-must-use
`
If missing, reinstall it:
sh
npm install --save-dev eslint-plugin-neverthrow-must-use
`$3
Run:
sh
npx eslint --ext .ts,.tsx src
`
If you see an error like:
Cannot read file 'tsconfig.json': ENOENT: no such file or directory
Make sure ---
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