member-delimiter-style
Require a specific member delimiter style for interfaces and type literals.
Some problems reported by this rule are automatically fixable by the --fix
ESLint command line option.
TypeScript allows three delimiters between members in interfaces and type aliases:
interface Foo {
// Semicolons (default, preferred in TypeScript):
name: string;
// Commas (JSON-like):
name: string,
// Line breaks (none):
name: string
}
For code readability, it's generally best to use the same style consistently in your codebase.
This rule enforces keeping to one configurable code style. It can also standardize the presence (or absence) of a delimiter in the last member of a construct, as well as a separate delimiter syntax for single line declarations.
module.exports = {
"rules": {
"@typescript-eslint/member-delimiter-style": "warn"
}
};
Options
This rule accepts an options object with the following properties:
interface Options {
multiline?: {
delimiter?: "none" | "semi" | "comma";
requireLast?: boolean;
};
singleline?: {
delimiter?: "semi" | "comma";
requireLast?: boolean;
};
overrides?: {
interface?: {
multiline?: {
delimiter?: "none" | "semi" | "comma";
requireLast?: boolean;
};
singleline?: {
delimiter?: "semi" | "comma";
requireLast?: boolean;
};
};
typeLiteral?: {
multiline?: {
delimiter?: "none" | "semi" | "comma";
requireLast?: boolean;
};
singleline?: {
delimiter?: "semi" | "comma";
requireLast?: boolean;
};
};
};
multilineDetection?: "brackets" | "last-member";
}
const defaultOptions: Options = [
{
multiline: { delimiter: "semi", requireLast: true },
singleline: { delimiter: "semi", requireLast: false },
multilineDetection: "brackets",
},
];
Default config:
{
"multiline": {
"delimiter": "semi",
"requireLast": true
},
"singleline": {
"delimiter": "semi",
"requireLast": false
},
"multilineDetection": "brackets"
}
multiline
config only applies to multiline interface
/type
definitions.
singleline
config only applies to single line interface
/type
definitions.
The two configs are entirely separate, and do not effect one another.
multilineDetection
determines what counts as multiline
"brackets"
(default) any newlines in the type or interface make it multiline."last-member"
if the last member of the interface is on the same line as the last bracket, it is counted as a single line.
delimiter
Accepts three values (or two for singleline
):
comma
- each member should be delimited with a comma (,
).semi
- each member should be delimited with a semicolon (;
).none
- each member should be delimited with nothing.
none
is not an option for singleline
because having no delimiter between members on a single line is a syntax error in TS.
requireLast
Determines whether or not the last member in the interface
/type
should have a delimiter:
true
- the last member must have a delimiter.false
- the last member must not have a delimiter.
overrides
Allows you to specify options specifically for either interface
s or type
definitions / inline type
s.
For example, to require commas for type
s, and semicolons for multiline interface
s:
{
"multiline": {
"delimiter": "comma",
"requireLast": true
},
"singleline": {
"delimiter": "comma",
"requireLast": true
},
"overrides": {
"interface": {
"multiline": {
"delimiter": "semi",
"requireLast": true
}
}
}
}
Examples
Examples of code for this rule with the default config:
- ❌ Incorrect
- ✅ Correct
// missing semicolon delimiter
interface Foo {
name: string
greet(): string
}
// using incorrect delimiter
interface Bar {
name: string,
greet(): string,
}
// missing last member delimiter
interface Baz {
name: string;
greet(): string
}
// incorrect delimiter
type FooBar = { name: string, greet(): string }
// last member should not have delimiter
type FooBar = { name: string; greet(): string; }
interface Foo {
name: string;
greet(): string;
}
interface Foo { name: string }
type Bar = {
name: string;
greet(): string;
}
type Bar = { name: string }
type FooBar = { name: string; greet(): string }
When Not To Use It
If you don't care about enforcing a consistent member delimiter in interfaces and type literals, then you will not need this rule.