ApplyDefaultOptions

type PathsOptions = {maxRecursionDepth?: number; leavesOnly?: boolean};
type DefaultPathsOptions = {maxRecursionDepth: 10; leavesOnly: false};
type SpecifiedOptions = {leavesOnly: true};

type Result = ApplyDefaultOptions<PathsOptions, DefaultPathsOptions, SpecifiedOptions>;
//=> {maxRecursionDepth: 10; leavesOnly: true}

// Complains if default values are not provided for optional options

type PathsOptions = {maxRecursionDepth?: number; leavesOnly?: boolean};
type DefaultPathsOptions = {maxRecursionDepth: 10};
type SpecifiedOptions = {};

type Result = ApplyDefaultOptions<PathsOptions, DefaultPathsOptions, SpecifiedOptions>;
//                                              ~~~~~~~~~~~~~~~~~~~
// Property 'leavesOnly' is missing in type 'DefaultPathsOptions' but required in type '{ maxRecursionDepth: number; leavesOnly: boolean; }'.

// Complains if an option's default type does not conform to the expected type

type PathsOptions = {maxRecursionDepth?: number; leavesOnly?: boolean};
type DefaultPathsOptions = {maxRecursionDepth: 10; leavesOnly: 'no'};
type SpecifiedOptions = {};

type Result = ApplyDefaultOptions<PathsOptions, DefaultPathsOptions, SpecifiedOptions>;
//                                              ~~~~~~~~~~~~~~~~~~~
// Types of property 'leavesOnly' are incompatible. Type 'string' is not assignable to type 'boolean'.

// Complains if an option's specified type does not conform to the expected type

type PathsOptions = {maxRecursionDepth?: number; leavesOnly?: boolean};
type DefaultPathsOptions = {maxRecursionDepth: 10; leavesOnly: false};
type SpecifiedOptions = {leavesOnly: 'yes'};

type Result = ApplyDefaultOptions<PathsOptions, DefaultPathsOptions, SpecifiedOptions>;
//                                                                   ~~~~~~~~~~~~~~~~
// Types of property 'leavesOnly' are incompatible. Type 'string' is not assignable to type 'boolean'.