fix: add better support for readonly types

BREAKING CHANGE: interface DeepMergeMergeFunctionURItoKind's signature has changed
RebeccaStevens · Nov 22, 2021 · 8daeaa0 · 8daeaa0
1 parent b317e60
commit 8daeaa0
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Showing 10 changed files with 194 additions and 175 deletions.
diff --git a/docs/deepmergeCustom.md b/docs/deepmergeCustom.md
@@ -37,7 +37,7 @@ This can be done using [Declaration Merging](https://www.typescriptlang.org/docs
 
 ```ts
 declare module "deepmerge-ts" {
-  interface DeepMergeMergeFunctionURItoKind<Ts extends ReadonlyArray<unknown>, MF extends DeepMergeMergeFunctionsURIs> {
+  interface DeepMergeMergeFunctionURItoKind<Ts extends Readonly<ReadonlyArray<unknown>>, MF extends DeepMergeMergeFunctionsURIs> {
     readonly MyCustomMergeURI: MyValue;
   }
 }
@@ -70,17 +70,16 @@ customDeepmerge(x, y, z); // => { foo: [Date, Date, Date] }
 
 declare module "deepmerge-ts" {
   interface DeepMergeMergeFunctionURItoKind<
-    Ts extends ReadonlyArray<unknown>,
+    Ts extends Readonly<ReadonlyArray<unknown>>,
     MF extends DeepMergeMergeFunctionsURIs
   > {
     readonly MyDeepMergeDatesURI: EveryIsDate<Ts> extends true ? Ts : DeepMergeLeaf<Ts>;
   }
 }
 
-type EveryIsDate<Ts extends ReadonlyArray<unknown>> = Ts extends readonly [
-  infer Head,
-  ...infer Rest
-]
+type EveryIsDate<Ts extends Readonly<ReadonlyArray<unknown>>> = Ts extends Readonly<
+  readonly [infer Head, ...infer Rest]
+>
   ? Head extends Date
     ? EveryIsDate<Rest>
     : false

diff --git a/src/deepmerge.ts b/src/deepmerge.ts
@@ -36,8 +36,8 @@ export type DeepMergeMergeFunctionsDefaults = typeof defaultOptions;
  *
  * @param objects - The objects to merge.
  */
-export function deepmerge<Ts extends ReadonlyArray<unknown>>(
-  ...objects: readonly [...Ts]
+export function deepmerge<Ts extends Readonly<ReadonlyArray<unknown>>>(
+  ...objects: Readonly<readonly [...Ts]>
 ): DeepMergeHKT<Ts, DeepMergeMergeFunctionsDefaultURIs> {
   return deepmergeCustom({})(...objects) as DeepMergeHKT<
     Ts,
@@ -54,13 +54,13 @@ export function deepmergeCustom<
   PMF extends Partial<DeepMergeMergeFunctionsURIs>
 >(
   options: DeepMergeOptions
-): <Ts extends ReadonlyArray<unknown>>(
+): <Ts extends Readonly<ReadonlyArray<unknown>>>(
   ...objects: Ts
 ) => DeepMergeHKT<Ts, GetDeepMergeMergeFunctionsURIs<PMF>> {
   /**
    * The type of the customized deepmerge function.
    */
-  type CustomizedDeepmerge = <Ts extends ReadonlyArray<unknown>>(
+  type CustomizedDeepmerge = <Ts extends Readonly<ReadonlyArray<unknown>>>(
     ...objects: Ts
   ) => DeepMergeHKT<Ts, GetDeepMergeMergeFunctionsURIs<PMF>>;
 
@@ -69,7 +69,7 @@ export function deepmergeCustom<
   /**
    * The customized deepmerge function.
    */
-  function customizedDeepmerge(...objects: ReadonlyArray<unknown>) {
+  function customizedDeepmerge(...objects: Readonly<ReadonlyArray<unknown>>) {
     if (objects.length === 0) {
       return undefined;
     }
@@ -112,7 +112,7 @@ function getUtils(
  * @param values - The values.
  */
 function mergeUnknowns<
-  Ts extends ReadonlyArray<unknown>,
+  Ts extends Readonly<ReadonlyArray<unknown>>,
   U extends DeepMergeMergeFunctionUtils,
   MF extends DeepMergeMergeFunctionsURIs
 >(values: Ts, utils: U): DeepMergeHKT<Ts, MF> {
@@ -136,25 +136,29 @@ function mergeUnknowns<
   switch (type) {
     case ObjectType.RECORD:
       return utils.mergeFunctions.mergeRecords(
-        values as ReadonlyArray<Readonly<Record<PropertyKey, unknown>>>,
+        values as Readonly<
+          ReadonlyArray<Readonly<Record<PropertyKey, unknown>>>
+        >,
         utils
       ) as DeepMergeHKT<Ts, MF>;
 
     case ObjectType.ARRAY:
       return utils.mergeFunctions.mergeArrays(
-        values as ReadonlyArray<ReadonlyArray<unknown>>,
+        values as Readonly<ReadonlyArray<Readonly<ReadonlyArray<unknown>>>>,
         utils
       ) as DeepMergeHKT<Ts, MF>;
 
     case ObjectType.SET:
       return utils.mergeFunctions.mergeSets(
-        values as ReadonlyArray<Readonly<ReadonlySet<unknown>>>,
+        values as Readonly<ReadonlyArray<Readonly<ReadonlySet<unknown>>>>,
         utils
       ) as DeepMergeHKT<Ts, MF>;
 
     case ObjectType.MAP:
       return utils.mergeFunctions.mergeMaps(
-        values as ReadonlyArray<Readonly<ReadonlyMap<unknown, unknown>>>,
+        values as Readonly<
+          ReadonlyArray<Readonly<ReadonlyMap<unknown, unknown>>>
+        >,
         utils
       ) as DeepMergeHKT<Ts, MF>;
 
@@ -172,7 +176,7 @@ function mergeUnknowns<
  * @param values - The records.
  */
 function mergeRecords<
-  Ts extends ReadonlyArray<Record<PropertyKey, unknown>>,
+  Ts extends Readonly<ReadonlyArray<Record<PropertyKey, unknown>>>,
   U extends DeepMergeMergeFunctionUtils,
   MF extends DeepMergeMergeFunctionsURIs
 >(values: Ts, utils: U) {
@@ -208,7 +212,7 @@ function mergeRecords<
  * @param values - The arrays.
  */
 function mergeArrays<
-  Ts extends ReadonlyArray<ReadonlyArray<unknown>>,
+  Ts extends Readonly<ReadonlyArray<Readonly<ReadonlyArray<unknown>>>>,
   U extends DeepMergeMergeFunctionUtils,
   MF extends DeepMergeMergeFunctionsURIs
 >(values: Ts, utils: U) {
@@ -221,7 +225,7 @@ function mergeArrays<
  * @param values - The sets.
  */
 function mergeSets<
-  Ts extends ReadonlyArray<Readonly<ReadonlySet<unknown>>>,
+  Ts extends Readonly<ReadonlyArray<Readonly<ReadonlySet<unknown>>>>,
   U extends DeepMergeMergeFunctionUtils,
   MF extends DeepMergeMergeFunctionsURIs
 >(values: Ts, utils: U) {
@@ -237,7 +241,7 @@ function mergeSets<
  * @param values - The maps.
  */
 function mergeMaps<
-  Ts extends ReadonlyArray<Readonly<ReadonlyMap<unknown, unknown>>>,
+  Ts extends Readonly<ReadonlyArray<Readonly<ReadonlyMap<unknown, unknown>>>>,
   U extends DeepMergeMergeFunctionUtils,
   MF extends DeepMergeMergeFunctionsURIs
 >(values: Ts, utils: U) {
@@ -253,7 +257,7 @@ function mergeMaps<
  * @param values - The values.
  */
 function leaf<
-  Ts extends ReadonlyArray<unknown>,
+  Ts extends Readonly<ReadonlyArray<unknown>>,
   U extends DeepMergeMergeFunctionUtils,
   MF extends DeepMergeMergeFunctionsURIs
 >(values: Ts, utils: U) {

diff --git a/src/types/defaults.ts b/src/types/defaults.ts
@@ -7,7 +7,6 @@ import type {
 import type {
   FlatternAlias,
   FilterOutNever,
-  IsNever,
   OptionalKeysOf,
   RequiredKeysOf,
   UnionMapKeys,
@@ -39,13 +38,13 @@ type DeepMergeMapsDefaultURI = "DeepMergeMapsDefaultURI";
 /**
  * The default merge functions to use when deep merging.
  */
-export type DeepMergeMergeFunctionsDefaultURIs = {
+export type DeepMergeMergeFunctionsDefaultURIs = Readonly<{
   DeepMergeRecordsURI: DeepMergeRecordsDefaultURI;
   DeepMergeArraysURI: DeepMergeArraysDefaultURI;
   DeepMergeSetsURI: DeepMergeSetsDefaultURI;
   DeepMergeMapsURI: DeepMergeMapsDefaultURI;
   DeepMergeOthersURI: DeepMergeLeafURI;
-};
+}>;
 
 /**
  * A union of all the props that should not be included in type information for
@@ -57,9 +56,9 @@ type BlacklistedRecordProps = "__proto__";
  * Deep merge records.
  */
 export type DeepMergeRecordsDefaultHKT<
-  Ts extends ReadonlyArray<unknown>,
+  Ts extends Readonly<ReadonlyArray<unknown>>,
   MF extends DeepMergeMergeFunctionsURIs
-> = Ts extends readonly [unknown, ...unknown[]]
+> = Ts extends Readonly<readonly [unknown, ...Readonly<ReadonlyArray<unknown>>]>
   ? FlatternAlias<
       Omit<
         DeepMergeRecordsDefaultHKTInternalProps<Ts, MF>,
@@ -72,7 +71,7 @@ export type DeepMergeRecordsDefaultHKT<
  * Deep merge record props.
  */
 type DeepMergeRecordsDefaultHKTInternalProps<
-  Ts extends readonly [unknown, ...unknown[]],
+  Ts extends Readonly<readonly [unknown, ...Readonly<ReadonlyArray<unknown>>]>,
   MF extends DeepMergeMergeFunctionsURIs
 > = {
   [K in OptionalKeysOf<Ts>]?: DeepMergeHKT<
@@ -90,22 +89,28 @@ type DeepMergeRecordsDefaultHKTInternalProps<
  * Get the value of the property.
  */
 type DeepMergeRecordsDefaultHKTInternalPropValue<
-  Ts extends readonly [unknown, ...unknown[]],
+  Ts extends Readonly<readonly [unknown, ...Readonly<ReadonlyArray<unknown>>]>,
   K extends PropertyKey
 > = FilterOutNever<
-  DeepMergeRecordsDefaultHKTInternalPropValueHelper<Ts, K, []>
+  DeepMergeRecordsDefaultHKTInternalPropValueHelper<
+    Ts,
+    K,
+    Readonly<readonly []>
+  >
 >;
 
 /**
  * Tail-recursive helper type for DeepMergeRecordsDefaultHKTInternalPropValue.
  */
 type DeepMergeRecordsDefaultHKTInternalPropValueHelper<
-  Ts extends readonly [unknown, ...unknown[]],
+  Ts extends Readonly<readonly [unknown, ...Readonly<ReadonlyArray<unknown>>]>,
   K extends PropertyKey,
-  Acc extends ReadonlyArray<unknown>
-> = Ts extends readonly [infer Head, ...infer Rest]
+  Acc extends Readonly<ReadonlyArray<unknown>>
+> = Ts extends Readonly<readonly [infer Head, ...infer Rest]>
   ? Head extends Record<PropertyKey, unknown>
-    ? Rest extends readonly [unknown, ...unknown[]]
+    ? Rest extends Readonly<
+        readonly [unknown, ...Readonly<ReadonlyArray<unknown>>]
+      >
       ? DeepMergeRecordsDefaultHKTInternalPropValueHelper<
           Rest,
           K,
@@ -119,22 +124,22 @@ type DeepMergeRecordsDefaultHKTInternalPropValueHelper<
  * Deep merge 2 arrays.
  */
 export type DeepMergeArraysDefaultHKT<
-  Ts extends ReadonlyArray<unknown>,
+  Ts extends Readonly<ReadonlyArray<unknown>>,
   MF extends DeepMergeMergeFunctionsURIs
 > = DeepMergeArraysDefaultHKTHelper<Ts, MF, []>;
 
 /**
  * Tail-recursive helper type for DeepMergeArraysDefaultHKT.
  */
 type DeepMergeArraysDefaultHKTHelper<
-  Ts extends ReadonlyArray<unknown>,
+  Ts extends Readonly<ReadonlyArray<unknown>>,
   MF extends DeepMergeMergeFunctionsURIs,
-  Acc extends ReadonlyArray<unknown>
+  Acc extends Readonly<ReadonlyArray<unknown>>
 > = Ts extends readonly [infer Head, ...infer Rest]
-  ? Head extends ReadonlyArray<unknown>
+  ? Head extends Readonly<ReadonlyArray<unknown>>
     ? Rest extends readonly [
-        ReadonlyArray<unknown>,
-        ...ReadonlyArray<unknown[]>
+        Readonly<ReadonlyArray<unknown>>,
+        ...Readonly<ReadonlyArray<Readonly<ReadonlyArray<unknown>>>>
       ]
       ? DeepMergeArraysDefaultHKTHelper<Rest, MF, [...Acc, ...Head]>
       : [...Acc, ...Head]
@@ -145,15 +150,15 @@ type DeepMergeArraysDefaultHKTHelper<
  * Deep merge 2 sets.
  */
 export type DeepMergeSetsDefaultHKT<
-  Ts extends ReadonlyArray<unknown>,
+  Ts extends Readonly<ReadonlyArray<unknown>>,
   MF extends DeepMergeMergeFunctionsURIs
 > = Set<UnionSetValues<Ts>>;
 
 /**
  * Deep merge 2 maps.
  */
 export type DeepMergeMapsDefaultHKT<
-  Ts extends ReadonlyArray<unknown>,
+  Ts extends Readonly<ReadonlyArray<unknown>>,
   MF extends DeepMergeMergeFunctionsURIs
 > = Map<UnionMapKeys<Ts>, UnionMapValues<Ts>>;
 
@@ -162,7 +167,7 @@ export type DeepMergeMapsDefaultHKT<
  */
 export type GetDeepMergeMergeFunctionsURIs<
   PMF extends Partial<DeepMergeMergeFunctionsURIs>
-> = {
+> = Readonly<{
   // prettier-ignore
   DeepMergeRecordsURI:
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -197,4 +202,4 @@ export type GetDeepMergeMergeFunctionsURIs<
     PMF["DeepMergeOthersURI"] extends keyof DeepMergeMergeFunctionURItoKind<any, any>
       ? PMF["DeepMergeOthersURI"]
       : DeepMergeLeafURI;
-};
+}>;