noThenProperty

JavaScript (and super languages)

Summary

Rule available since: v1.5.0
Diagnostic Category: lint/suspicious/noThenProperty
This rule is recommended, meaning it is enabled by default.
This rule doesn’t have a fix.
The default severity of this rule is error.
Sources:
- Same as unicorn/no-thenable

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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        "noThenProperty": "error"
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      }
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    }
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  }
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}

Description

Disallow then property.

When combining objects with a then method (thenable objects) with await expressions or dynamic imports, caution is necessary. These syntaxes interpret the object’s then method as intended for the resolution or rejection of a promise, which can lead to unexpected behavior or errors.

Examples

Invalid

1
export {then};

code-block.js:1:9 lint/suspicious/noThenProperty ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This export exposes the name then.
  
  > 1 │ export {then};
      │         ^^^^
    2 │ 
  
  ℹ Values with a then property can be treated like promises by await and dynamic imports, which can cause unexpected behavior.
  
  ℹ Export this value under a different name, or rename the declaration so it does not expose then.

1
const foo = {
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    then() {}
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};

code-block.js:2:5 lint/suspicious/noThenProperty ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This object defines a then property.
  
    1 │ const foo = {
  > 2 │     then() {}
      │     ^^^^
    3 │ };
    4 │ 
  
  ℹ Values with a then property can be treated like promises by await and dynamic imports, which can cause unexpected behavior.
  
  ℹ Rename this property to something other than then unless you intentionally need a thenable object.

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const foo = {
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    get then() {}
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};

code-block.js:2:9 lint/suspicious/noThenProperty ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This object defines a then property.
  
    1 │ const foo = {
  > 2 │     get then() {}
      │         ^^^^
    3 │ };
    4 │ 
  
  ℹ Values with a then property can be treated like promises by await and dynamic imports, which can cause unexpected behavior.
  
  ℹ Rename this property to something other than then unless you intentionally need a thenable object.

1
const foo = {
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   get then() {}
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};

code-block.js:2:8 lint/suspicious/noThenProperty ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This object defines a then property.
  
    1 │ const foo = {
  > 2 │    get then() {}
      │        ^^^^
    3 │ };
    4 │ 
  
  ℹ Values with a then property can be treated like promises by await and dynamic imports, which can cause unexpected behavior.
  
  ℹ Rename this property to something other than then unless you intentionally need a thenable object.

1
foo.then = function () {}

code-block.js:1:1 lint/suspicious/noThenProperty ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This object defines a then property.
  
  > 1 │ foo.then = function () {}
      │ ^^^^^^^^
    2 │ 
  
  ℹ Values with a then property can be treated like promises by await and dynamic imports, which can cause unexpected behavior.
  
  ℹ Rename this property to something other than then unless you intentionally need a thenable object.

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class Foo {
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    then() {}
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}

code-block.js:2:5 lint/suspicious/noThenProperty ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This class defines a then member.
  
    1 │ class Foo {
  > 2 │     then() {}
      │     ^^^^
    3 │ }
    4 │ 
  
  ℹ Values with a then property can be treated like promises by await and dynamic imports, which can cause unexpected behavior.
  
  ℹ Rename this member to something other than then unless you intentionally need a thenable class.

1
class Foo {
2
    static then() {}
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}

code-block.js:2:12 lint/suspicious/noThenProperty ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

  ✖ This class defines a then member.
  
    1 │ class Foo {
  > 2 │     static then() {}
      │            ^^^^
    3 │ }
    4 │ 
  
  ℹ Values with a then property can be treated like promises by await and dynamic imports, which can cause unexpected behavior.
  
  ℹ Rename this member to something other than then unless you intentionally need a thenable class.

Valid

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export {then as success};

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const foo = {
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    success() {}
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};

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class Foo {
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    success() {}
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}

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const foo = bar.then;