@pulumi/eslint-plugin

A simple eslint plugin for the Pulumi Node SDK.

Motivation

Because Pulumi generates several nontrivial types, and those types often have some nontrivial semantics backing them, it can be the case where some idioms have been implemented to help prevent footgunning. Rather than allowing those footguns to occur, it seems better to point them out and (where possible) offer helpful advice to prevent them as early as possible. Thankfully, ESLint and TypeScript offer a very early escape hatch for this sort of thing, and so this plugin was born.

Examples

no-output-in-template-literal

This rule is intended to prevent objects of type pulumi.Output<T> from appearing in template strings. It seems obvious that if we have an Output<string> that template interpolation would work out of the box, but we can't rely on that value to be set at the time the interpolation occurs. In this case, we provide the pulumi.interpolate template tag to ensure the Output value is resolved correctly.

Invalid:

import * as pulumi from "@pulumi/pulumi";
import * as aws from "@pulumi/aws";

const myBucket = new aws.s3.Bucket("myBucket");
const bucketArn = myBucket.arn;
const someInterpolatedString = `${bucketArn}`;

Valid:

import * as pulumi from "@pulumi/pulumi";
import * as aws from "@pulumi/aws";

const myBucket = new aws.s3.Bucket("myBucket");
const bucketArn = myBucket.arn;
const someInterpolatedString = pulumi.interpolate`${bucketArn}`;

no-output-instance-in-template-literal

This rule is very similar to no-output-in-template-literal, and is intended to prevent objects of type pulumi.OutputInstance<T> from appearing in template strings.

Invalid:

import * as pulumi from "@pulumi/pulumi";

const outputInstance: pulumi.OutputInstance<number> = pulumi.output([1, 2, 3])[0];
const someInterpolatedString = `${outputInstance}`

Valid:

import * as pulumi from "@pulumi/pulumi";

const outputInstance: pulumi.OutputInstance<number> = pulumi.output([1, 2, 3])[0];
const someInterpolatedString = pulumi.interpolate`${outputInstance}`

Contributing

Adding a rule is meant to be as simple as possible. For any check we want to make, it's likely best to build a simple example in AST Explorer first. Then, determine the rules governing the node which breaks the rule we want to implement. From that point, we can use the helper ESLintUtils.RuleCreator to handle much of the boilerplate needed to build our new rule. Many of the patterns used from there are visible in the no-output-in-template-literal rule. From there, register the new rule in index.ts, and write a new test suite in tests. See example.