feat: Add AtLeastOne type

docs/custom-types.md

@@ -0,0 +1,41 @@
+# Custom types
+
+`AtLeastOne`
+
+Can be used when you want to make at least one key of an object required.
+You don't have to specify which key should be required, it will be inferred from the input type.
+Useful for example when you have a function that requires at least one of the parameters, but not necessarily all of them.
+
+```typescript
+type TestType = {
+    a: string;
+    b: number;
+}
+
+const foo = (params: AtLeastOne<TestType>) => {
+    // ...
+}
+
+// Valid
+foo({ a: 'a' });
+foo({ b: 1 });
+foo({ a: 'a', b: 1 });
+
+// Invalid
+foo({});
+```
+
+`MayOmit`
+
+Makes K keys optional in T.
+Can be used to provide some defaults and merge input on top of it.
+Requires you to explicitly specify which keys should be optional.
+
+```typescript
+type TestType = {
+    a: string;
+    b: number;
+}
+
+type TestTypeWithOptionalB = MayOmit<TestType, 'b'>;
+```

src/common/atLeastOne.spec.ts

@@ -0,0 +1,21 @@
+import { assertType } from 'vitest'
+import type { AtLeastOne } from './atLeastOne'
+
+describe('AtLeastOne', () => {
+  it('makes at least one key of an object required', () => {
+    interface TestType {
+      a: string
+      b: number
+    }
+
+    const testCase1: AtLeastOne<TestType> = { a: 'a' }
+    assertType<{ a: string; b?: number }>(testCase1)
+
+    const testCase2: AtLeastOne<TestType> = { b: 1 }
+    assertType<{ a?: string; b: number }>(testCase2)
+
+    // @ts-expect-error wrong types
+    const testCase3: AtLeastOne<TestType> = {}
+    assertType(testCase3)
+  })
+})

src/common/atLeastOne.ts

@@ -0,0 +1 @@
+export type AtLeastOne<T, U = { [K in keyof T]: Pick<T, K> }> = Partial<T> & U[keyof U]

src/index.ts

@@ -16,11 +16,11 @@ export { isEntityGoneError } from './errors/errorTypeGuards'
 export { ConfigScope } from './config/ConfigScope'
 export { ensureClosingSlashTransformer } from './config/configTransformers'
 export { createRangeValidator } from './config/configValidators'
-export {
-  type EnvValueValidator,
-  type EnvValueTransformer,
-  type AppConfig,
-  type RedisConfig,
+export type {
+  EnvValueValidator,
+  EnvValueTransformer,
+  AppConfig,
+  RedisConfig,
 } from './config/configTypes'
 
 export {
@@ -61,7 +61,7 @@ export {
   isObject,
   hasMessage,
 } from './utils/typeUtils'
-export { type StandardizedError } from './utils/typeUtils'
+export type { StandardizedError } from './utils/typeUtils'
 
 export { generateHash, HashAlgorithm, HashEncoding } from './utils/hashUtils'
 
@@ -74,10 +74,10 @@ export {
 export type { AppLoggerConfig, MonorepoAppLoggerConfig } from './logging/loggerConfigResolver'
 export type { CommonLogger } from './logging/commonLogger'
 
-export {
-  type ErrorReport,
-  type ErrorReporter,
-  type ErrorResolver,
+export type {
+  ErrorReport,
+  ErrorReporter,
+  ErrorResolver,
 } from './errors/errorReporterTypes'
 export {
   executeAsyncAndHandleGlobalErrors,
@@ -87,8 +87,9 @@ export {
   resolveGlobalErrorLogObject,
 } from './errors/globalErrorHandler'
 
-export { type MayOmit } from './common/may-omit'
-export { type FreeformRecord } from './common/commonTypes'
+export type { MayOmit } from './common/may-omit'
+export type { FreeformRecord } from './common/commonTypes'
+export type { AtLeastOne } from './common/atLeastOne'
 export {
   type ValidationError,
   type CommonErrorParams,

vitest.config.mts

@@ -30,5 +30,17 @@ export default defineConfig({
         statements: 100,
       },
     },
+    typecheck: {
+      enabled: true,
+      /**
+       * By default, vitest runs typecheck on tests matching the pattern "*.test-d.ts".
+       * Sadly some IDEs (like Webstorm) doesn't work well with custom patterns like that.
+       * They do not properly recognize globals like vitest ones (describe, it, expect, etc.).
+       * Because of that, we include typecheck in all test files.
+       * The performance impact is minimal, and it makes the IDE work properly.
+       * Docs: https://vitest.dev/guide/testing-types.html#testing-types
+       */
+      include: ['src/**/*.spec.ts'],
+    },
   },
 })