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eb39fafa4f
includes a (minimal) working wrapper Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
80 lines
2.7 KiB
Markdown
80 lines
2.7 KiB
Markdown
# require using Error objects as Promise rejection reasons (prefer-promise-reject-errors)
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It is considered good practice to only pass instances of the built-in `Error` object to the `reject()` function for user-defined errors in Promises. `Error` objects automatically store a stack trace, which can be used to debug an error by determining where it came from. If a Promise is rejected with a non-`Error` value, it can be difficult to determine where the rejection occurred.
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## Rule Details
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This rule aims to ensure that Promises are only rejected with `Error` objects.
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## Options
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This rule takes one optional object argument:
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* `allowEmptyReject: true` (`false` by default) allows calls to `Promise.reject()` with no arguments.
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Examples of **incorrect** code for this rule:
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```js
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/*eslint prefer-promise-reject-errors: "error"*/
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Promise.reject("something bad happened");
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Promise.reject(5);
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Promise.reject();
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new Promise(function(resolve, reject) {
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reject("something bad happened");
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});
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new Promise(function(resolve, reject) {
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reject();
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});
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```
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Examples of **correct** code for this rule:
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```js
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/*eslint prefer-promise-reject-errors: "error"*/
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Promise.reject(new Error("something bad happened"));
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Promise.reject(new TypeError("something bad happened"));
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new Promise(function(resolve, reject) {
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reject(new Error("something bad happened"));
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});
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var foo = getUnknownValue();
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Promise.reject(foo);
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```
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Examples of **correct** code for this rule with the `allowEmptyReject: true` option:
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```js
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/*eslint prefer-promise-reject-errors: ["error", {"allowEmptyReject": true}]*/
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Promise.reject();
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new Promise(function(resolve, reject) {
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reject();
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});
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```
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## Known Limitations
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Due to the limits of static analysis, this rule cannot guarantee that you will only reject Promises with `Error` objects. While the rule will report cases where it can guarantee that the rejection reason is clearly not an `Error`, it will not report cases where there is uncertainty about whether a given reason is an `Error`. For more information on this caveat, see the [similar limitations](no-throw-literal.md#known-limitations) in the `no-throw-literal` rule.
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To avoid conflicts between rules, this rule does not report non-error values used in `throw` statements in async functions, even though these lead to Promise rejections. To lint for these cases, use the [`no-throw-literal`](https://eslint.org/docs/rules/no-throw-literal) rule.
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## When Not To Use It
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If you're using custom non-error values as Promise rejection reasons, you can turn off this rule.
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## Further Reading
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* [`no-throw-literal`](https://eslint.org/docs/rules/no-throw-literal)
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* [Warning: a promise was rejected with a non-error](http://bluebirdjs.com/docs/warning-explanations.html#warning-a-promise-was-rejected-with-a-non-error)
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