noNonNullAssertedOptionalChain

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JavaScript (and super languages)

Summary

Rule available since: v2.1.4
Diagnostic Category: lint/suspicious/noNonNullAssertedOptionalChain
This rule is recommended, which means is enabled by default.
This rule doesn’t have a fix.
The default severity of this rule is error.
Sources:
- Same as @typescript-eslint/no-non-null-asserted-optional-chain

How to configure

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{
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  "linter": {
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    "rules": {
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      "suspicious": {
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        "noNonNullAssertedOptionalChain": "error"
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      }
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    }
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  }
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}

Description

Disallow non-null assertions after optional chaining expressions.

Optional chaining (?.) is designed to return undefined if the object is null or undefined. Using a non-null assertion (!) immediately after optional chaining defeats the purpose of optional chaining and can lead to runtime errors.

Examples

Invalid

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obj?.prop!;

code-block.ts:1:1 lint/suspicious/noNonNullAssertedOptionalChain ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Forbidden non-null assertion after optional chaining.
  
  > 1 │ obj?.prop!;
      │ ^^^^^^^^^^
    2 │ 
  
  ℹ Optional chaining already handles nullish values. Using non-null assertion defeats its purpose and may cause runtime errors.
  
  ℹ Consider using the nullish coalescing operator ?? or optional chaining throughout the chain instead.

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obj?.method()!.prop;

code-block.ts:1:1 lint/suspicious/noNonNullAssertedOptionalChain ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Forbidden non-null assertion after optional chaining.
  
  > 1 │ obj?.method()!.prop;
      │ ^^^^^^^^^^^^^^
    2 │ 
  
  ℹ Optional chaining already handles nullish values. Using non-null assertion defeats its purpose and may cause runtime errors.
  
  ℹ Consider using the nullish coalescing operator ?? or optional chaining throughout the chain instead.

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obj?.[key]!.method();

code-block.ts:1:1 lint/suspicious/noNonNullAssertedOptionalChain ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ Forbidden non-null assertion after optional chaining.
  
  > 1 │ obj?.[key]!.method();
      │ ^^^^^^^^^^^
    2 │ 
  
  ℹ Optional chaining already handles nullish values. Using non-null assertion defeats its purpose and may cause runtime errors.
  
  ℹ Consider using the nullish coalescing operator ?? or optional chaining throughout the chain instead.

Valid

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obj?.prop;

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obj!.prop?.method();

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obj?.prop ?? defaultValue;