type/no-unnecessary-condition

Disallow conditions that are always truthy, always falsy, never, or always nullish.

Applies to: Type information in Vue SFC scripts and templates, for the constructs shown below.

This rule reads type information from your TypeScript project (tsconfig.json), so the configuration sets typeAware: true. typeAware does not turn on opt-in rules by itself.

Bad

value is a string, so it is never nullish and the ?? fallback never runs.

<script setup lang="ts">
function orDefault(value: string): string {
  return value ?? "x";
}
</script>

Good

value may be undefined, so the ?? fallback supplies a string when it is missing.

<script setup lang="ts">
function orDefault(value: string | undefined): string {
  return value ?? "x";
}
</script>

Configuration (Vite+)

import { defineConfig } from "@vizejs/vite-plugin/vite-plus";

export default defineConfig({}).withVue({
  linter: {
    "preset": "incremental",
    "rules": {
      "type/no-unnecessary-condition": "warn"
    },
    "typeAware": true
  },
});

Then run vp run lint.

Related

• Type and script rules
• Rule options
• All rules
• Source code