Add ScreamingSnakeCase type (#214)

Co-authored-by: Sindre Sorhus <[email protected]>

readme.md

@@ -136,6 +136,7 @@ Click the type names for complete docs.
 - [`SnakeCase`](ts41/snake-case.d.ts) – Convert a string literal to snake-case (`foo_bar`).
 - [`SnakeCasedProperties`](ts41/snake-cased-properties-deep.d.ts) – Convert object properties to snake-case (`foo_bar`).
 - [`SnakeCasedPropertiesDeep`](ts41/snake-cased-properties-deep.d.ts) – Convert object properties to snake-case recursively (`foo_bar`).
+- [`ScreamingSnakeCase`](ts41/screaming-snake-case.d.ts) - Convert a string literal to screaming-snake-case (`FOO_BAR`).
 - [`DelimiterCase`](ts41/delimiter-case.d.ts) – Convert a string literal to a custom string delimiter casing.
 - [`DelimiterCasedProperties`](ts41/delimiter-cased-properties.d.ts) – Convert object properties to a custom string delimiter casing.
 - [`DelimiterCasedPropertiesDeep`](ts41/delimiter-cased-properties-deep.d.ts) – Convert object properties to a custom string delimiter casing recursively.

test-d/screaming-snake-case.ts

@@ -0,0 +1,23 @@
+import {ScreamingSnakeCase} from '../ts41/screaming-snake-case';
+import {expectType} from 'tsd';
+
+const screamingSnakeFromCamel: ScreamingSnakeCase<'fooBar'> = 'FOO_BAR';
+expectType<'FOO_BAR'>(screamingSnakeFromCamel);
+
+const screamingSnakeFromKebab: ScreamingSnakeCase<'foo-bar'> = 'FOO_BAR';
+expectType<'FOO_BAR'>(screamingSnakeFromKebab);
+
+const screamingSnakeFromSpace: ScreamingSnakeCase<'foo bar'> = 'FOO_BAR';
+expectType<'FOO_BAR'>(screamingSnakeFromSpace);
+
+const screamingSnakeFromSnake: ScreamingSnakeCase<'foo_bar'> = 'FOO_BAR';
+expectType<'FOO_BAR'>(screamingSnakeFromSnake);
+
+const screamingSnakeFromScreamingSnake: ScreamingSnakeCase<'FOO_BAR'> = 'FOO_BAR';
+expectType<'FOO_BAR'>(screamingSnakeFromScreamingSnake);
+
+const noScreamingSnakeFromMono: ScreamingSnakeCase<'foobar'> = 'FOOBAR';
+expectType<'FOOBAR'>(noScreamingSnakeFromMono);
+
+const nonStringFromNonString: ScreamingSnakeCase<[]> = [];
+expectType<[]>(nonStringFromNonString);

ts41/index.d.ts

@@ -14,6 +14,7 @@ export {PascalCasedPropertiesDeep} from './pascal-cased-properties-deep';
 export {SnakeCase} from './snake-case';
 export {SnakeCasedProperties} from './snake-cased-properties';
 export {SnakeCasedPropertiesDeep} from './snake-cased-properties-deep';
+export {ScreamingSnakeCase} from './screaming-snake-case';
 export {DelimiterCase} from './delimiter-case';
 export {DelimiterCasedProperties} from './delimiter-cased-properties';
 export {DelimiterCasedPropertiesDeep} from './delimiter-cased-properties-deep';

ts41/screaming-snake-case.d.ts

@@ -0,0 +1,40 @@
+import {SplitIncludingDelimiters} from './delimiter-case';
+import {SnakeCase} from './snake-case';
+
+/**
+Returns a boolean for whether the given array includes the given item.
+*/
+type Includes<Value extends any[], Item> = {
+	[P in keyof Value & number as Value[P]]: true;
+}[Item] extends true
+	? true
+	: false;
+
+/**
+Returns a boolean for whether the string is screaming snake case.
+*/
+type IsScreamingSnakeCase<Value extends string> = Value extends Uppercase<Value>
+	? Includes<SplitIncludingDelimiters<Lowercase<Value>, '_'>, '_'> extends true
+		? true
+		: false
+	: false;
+
+/**
+Convert a string literal to screaming-snake-case.
+
+This can be useful when, for example, converting a camel-cased object property to a screaming-snake-cased SQL column name.
+
+@example
+```
+import {ScreamingSnakeCase} from 'type-fest';
+
+const someVariable: ScreamingSnakeCase<'fooBar'> = 'FOO_BAR';
+```
+
+@category Template Literals
+*/
+export type ScreamingSnakeCase<Value> = Value extends string
+	? IsScreamingSnakeCase<Value> extends true
+		? Value
+		: Uppercase<SnakeCase<Value>>
+	: Value;