API: make map and set Matcher functions instead of custom patterns

Author: gvergnaud

README.md

@@ -951,9 +951,11 @@ console.log(output);
 // => 'a list of posts!'
 ```
 
-### Sets
+### `P.set` patterns
 
-Patterns can be Sets.
+To match a Set, you can use `P.set(subpattern)`.
+It takes a sub-pattern, and will match if **all elements** inside the set
+match this sub-pattern.
 
 ```ts
 import { match, P } from 'ts-pattern';
@@ -963,26 +965,20 @@ type Input = Set<string | number>;
 const input: Input = new Set([1, 2, 3]);
 
 const output = match(input)
-  .with(new Set([1, 'hello']), (set) => `Set contains 1 and 'hello'`)
-  .with(new Set([1, 2]), (set) => `Set contains 1 and 2`)
-  .with(new Set([P.string]), (set) => `Set contains only strings`)
-  .with(new Set([P.number]), (set) => `Set contains only numbers`)
+  .with(P.set(1), (set) => `Set contains only 1`)
+  .with(P.set(P.string), (set) => `Set contains only strings`)
+  .with(P.set(P.number), (set) => `Set contains only numbers`)
   .otherwise(() => '');
 
 console.log(output);
-// => 'Set contains 1 and 2'
+// => "Set contains only numbers"
 ```
 
-If a Set pattern contains one single wildcard pattern, it will match if
-each value in the input set match the wildcard.
+### `P.map` patterns
 
-If a Set pattern contains several values, it will match if the
-input Set contains each of these values.
-
-### Maps
-
-Patterns can be Maps. They match if the input is a Map, and if each
-value match the corresponding sub-pattern.
+To match a Map, you can use `P.map(keyPattern, valuePattern)`.
+It takes a subpattern to match against the key, a subpattern to match agains the value, and will match if **all elements** inside this map
+match these two sub-patterns.
 
 ```ts
 import { match, P } from 'ts-pattern';
@@ -996,19 +992,16 @@ const input: Input = new Map([
 ]);
 
 const output = match(input)
-  .with(new Map([['b', 2]]), (map) => `map.get('b') is 2`)
-  .with(new Map([['a', P.string]]), (map) => `map.get('a') is a string`)
+  .with(P.map(P.string, P.number), (map) => `map's type is Map<string, number>`)
+  .with(P.map(P.string, P.string), (map) => `map's type is Map<string, string>`)
   .with(
-    new Map([
-      ['a', P.number],
-      ['c', P.number],
-    ]),
-    (map) => `map.get('a') and map.get('c') are number`
+    P.map(P.union('a', 'c'), P.number),
+    (map) => `map's type is Map<'a' | 'c', number>`
   )
   .otherwise(() => '');
 
 console.log(output);
-// => 'map.get('b') is 2'
+// => "map's type is Map<string, number>"
 ```
 
 ### `P.when` patterns

src/patterns.ts

@@ -7,6 +7,8 @@ import {
   UnknownPattern,
   OptionalP,
   ArrayP,
+  MapP,
+  SetP,
   AndP,
   OrP,
   NotP,
@@ -68,7 +70,14 @@ export function optional<
   };
 }
 
-type Elem<xs> = xs extends Array<infer x> ? x : never;
+type UnwrapArray<xs> = xs extends Array<infer x> ? x : never;
+
+type UnwrapSet<xs> = xs extends Set<infer x> ? x : never;
+
+type UnwrapMapKey<xs> = xs extends Map<infer k, any> ? k : never;
+
+type UnwrapMapValue<xs> = xs extends Map<any, infer v> ? v : never;
+
 type WithDefault<a, b> = [a] extends [never] ? b : a;
 
 /**
@@ -83,7 +92,7 @@ type WithDefault<a, b> = [a] extends [never] ? b : a;
  */
 export function array<
   input,
-  const p extends Pattern<WithDefault<Elem<input>, unknown>>
+  const p extends Pattern<WithDefault<UnwrapArray<input>, unknown>>
 >(pattern: p): ArrayP<input, p> {
   return {
     [symbols.matcher]() {
@@ -116,6 +125,109 @@ export function array<
   };
 }
 
+/**
+ * `P.set(subpattern)` takes a sub pattern and returns a pattern that matches
+ * sets if all their elements match the sub pattern.
+ *
+ * [Read `P.set` documentation on GitHub](https://github.com/gvergnaud/ts-pattern#Pset-patterns)
+ *
+ * @example
+ *  match(value)
+ *   .with({ users: P.set(P.string) }, () => 'will match Set<string>')
+ */
+export function set<
+  input,
+  const p extends Pattern<WithDefault<UnwrapSet<input>, unknown>>
+>(pattern: p): SetP<input, p> {
+  return {
+    [symbols.matcher]() {
+      return {
+        match: <I>(value: I | input) => {
+          if (!(value instanceof Set)) return { matched: false };
+
+          let selections: Record<string, unknown[]> = {};
+
+          if (value.size === 0) {
+            return { matched: true, selections };
+          }
+
+          const selector = (key: string, value: unknown) => {
+            selections[key] = (selections[key] || []).concat([value]);
+          };
+
+          const matched = setEvery(value, (v) =>
+            matchPattern(pattern, v, selector)
+          );
+
+          return { matched, selections };
+        },
+        getSelectionKeys: () => getSelectionKeys(pattern),
+      };
+    },
+  };
+}
+
+const setEvery = <T>(set: Set<T>, predicate: (value: T) => boolean) => {
+  for (const value of set) {
+    if (predicate(value)) continue
+    return false
+  }
+  return true
+}
+
+/**
+ * `P.set(subpattern)` takes a sub pattern and returns a pattern that matches
+ * sets if all their elements match the sub pattern.
+ *
+ * [Read `P.set` documentation on GitHub](https://github.com/gvergnaud/ts-pattern#Pset-patterns)
+ *
+ * @example
+ *  match(value)
+ *   .with({ users: P.set(P.string) }, () => 'will match Set<string>')
+ */
+export function map<
+  input,
+  const pkey extends Pattern<WithDefault<UnwrapMapKey<input>, unknown>>,
+  const pvalue extends Pattern<WithDefault<UnwrapMapValue<input>, unknown>>
+>(patternKey: pkey, patternValue: pvalue): MapP<input, pkey, pvalue> {
+  return {
+    [symbols.matcher]() {
+      return {
+        match: <I>(value: I | input) => {
+          if (!(value instanceof Map)) return { matched: false };
+
+          let selections: Record<string, unknown[]> = {};
+
+          if (value.size === 0) {
+            return { matched: true, selections };
+          }
+
+          const selector = (key: string, value: unknown) => {
+            selections[key] = (selections[key] || []).concat([value]);
+          };
+
+          const matched = mapEvery(value, (v, k) =>{
+            const keyMatch = matchPattern(patternKey, k, selector)
+            const valueMatch = matchPattern(patternValue, v, selector)
+            return keyMatch && valueMatch
+          });
+
+          return { matched, selections };
+        },
+        getSelectionKeys: () => getSelectionKeys(patternKey).concat(getSelectionKeys(patternValue)),
+      };
+    },
+  };
+}
+
+const mapEvery = <K, T>(map: Map<K, T>, predicate: (value: T, key: K) => boolean) => {
+  for (const [key, value] of map.entries()) {
+    if (predicate(value, key)) continue;
+    return false;
+  }
+  return true;
+}
+
 /**
  * `P.intersection(...patterns)` returns a pattern which matches
  * only if **every** patterns provided in parameter match the input.
@@ -474,7 +586,7 @@ export function instanceOf<T extends AnyConstructor>(
  *  )
  */
 export function typed<input>(): {
-  array<const p extends Pattern<Elem<input>>>(pattern: p): ArrayP<input, p>;
+  array<const p extends Pattern<UnwrapArray<input>>>(pattern: p): ArrayP<input, p>;
 
   optional<const p extends Pattern<input>>(pattern: p): OptionalP<input, p>;
 

src/types/FindSelected.ts

@@ -57,6 +57,9 @@ export type FindSelectionUnion<
       array: i extends readonly (infer ii)[]
         ? MapList<FindSelectionUnion<ii, pattern>>
         : never;
+      // FIXME: selection for map and set is supported at the value level
+      map: never;
+      set: never;
       optional: MapOptional<FindSelectionUnion<i, pattern>>;
       or: MapOptional<
         ReduceFindSelectionUnion<i, Extract<pattern, readonly any[]>>

src/types/InvertPattern.ts

@@ -46,6 +46,10 @@ export type InvertPattern<p> = p extends Matcher<
       not: ToExclude<InvertPattern<narrowed>>;
       select: InvertPattern<narrowed>;
       array: InvertPattern<narrowed>[];
+      map: narrowed extends [infer pk, infer pv]
+        ? Map<InvertPattern<pk>, InvertPattern<pv>>
+        : never;
+      set: Set<InvertPattern<narrowed>>;
       optional: InvertPattern<narrowed> | undefined;
       and: ReduceIntersection<Extract<narrowed, readonly any[]>>;
       or: ReduceUnion<Extract<narrowed, readonly any[]>>;
@@ -78,10 +82,6 @@ export type InvertPattern<p> = p extends Matcher<
     : p extends readonly []
     ? []
     : InvertPattern<pp>[]
-  : p extends Map<infer pk, infer pv>
-  ? Map<pk, InvertPattern<pv>>
-  : p extends Set<infer pv>
-  ? Set<InvertPattern<pv>>
   : IsPlainObject<p> extends true
   ? OptionalKeys<p> extends infer optKeys
     ? [optKeys] extends [never]
@@ -163,6 +163,17 @@ type InvertPatternForExcludeInternal<p, i, empty = never> =
         array: i extends readonly (infer ii)[]
           ? InvertPatternForExcludeInternal<subpattern, ii, empty>[]
           : empty;
+        map: subpattern extends [infer pk, infer pv]
+          ? i extends Map<infer ik, infer iv>
+            ? Map<
+                InvertPatternForExcludeInternal<pk, ik, empty>,
+                InvertPatternForExcludeInternal<pv, iv, empty>
+              >
+            : empty
+          : empty;
+        set: i extends Set<infer iv>
+          ? Set<InvertPatternForExcludeInternal<subpattern, iv, empty>>
+          : empty;
         optional:
           | InvertPatternForExcludeInternal<subpattern, i, empty>
           | undefined;
@@ -223,14 +234,6 @@ type InvertPatternForExcludeInternal<p, i, empty = never> =
         ? []
         : InvertPatternForExcludeInternal<pp, ii, empty>[]
       : empty
-    : p extends Map<infer pk, infer pv>
-    ? i extends Map<any, infer iv>
-      ? Map<pk, InvertPatternForExcludeInternal<pv, iv, empty>>
-      : empty
-    : p extends Set<infer pv>
-    ? i extends Set<infer iv>
-      ? Set<InvertPatternForExcludeInternal<pv, iv, empty>>
-      : empty
     : IsPlainObject<p> extends true
     ? i extends object
       ? [keyof p & keyof i] extends [never]

src/types/Pattern.ts

@@ -8,6 +8,8 @@ export type MatcherType =
   | 'or'
   | 'and'
   | 'array'
+  | 'map'
+  | 'set'
   | 'select'
   | 'default';
 
@@ -66,6 +68,10 @@ export type OptionalP<input, p> = Matcher<input, p, 'optional'>;
 
 export type ArrayP<input, p> = Matcher<input, p, 'array'>;
 
+export type MapP<input, pkey, pvalue> = Matcher<input, [pkey, pvalue], 'map'>;
+
+export type SetP<input, p> = Matcher<input, p, 'set'>;
+
 export type AndP<input, ps> = Matcher<input, ps, 'and'>;
 
 export type OrP<input, ps> = Matcher<input, ps, 'or'>;
@@ -98,8 +104,6 @@ export type UnknownPattern =
   | readonly []
   | readonly [UnknownPattern, ...UnknownPattern[]]
   | { readonly [k: string]: UnknownPattern }
-  | Set<UnknownPattern>
-  | Map<unknown, UnknownPattern>
   | Primitives
   | UnknownMatcher;
 
@@ -120,7 +124,7 @@ export type Pattern<a> = unknown extends a
 
 export type PatternInternal<
   a,
-  objs = Exclude<a, Primitives | readonly any[]>,
+  objs = Exclude<a, Primitives | Map<any, any> | Set<any> | readonly any[]>,
   arrays = Extract<a, readonly any[]>,
   primitives = Extract<a, Primitives>
 > =

tests/exhaustive-match.test.ts

@@ -432,13 +432,13 @@ describe('exhaustive()', () => {
       const input = new Set(['']) as Input;
 
       match(input)
-        .with(new Set([P.string]), (x) => x)
+        .with(P.set(P.string), (x) => x)
         // @ts-expect-error
         .exhaustive();
 
       match(input)
-        .with(new Set([P.string]), (x) => x)
-        .with(new Set([P.number]), (x) => new Set([]))
+        .with(P.set(P.string), (x) => x)
+        .with(P.set(P.number), (x) => new Set([]))
         .exhaustive();
     });
 
@@ -448,15 +448,15 @@ describe('exhaustive()', () => {
 
       expect(
         match(input)
-          .with(new Set([P.string]), (x) => x)
+          .with(P.set(P.string), (x) => x)
           // @ts-expect-error
           .exhaustive()
       ).toEqual(input);
 
       expect(
         match(input)
-          .with(new Set([P.string]), (x) => 1)
-          .with(new Set([P.number]), (x) => 2)
+          .with(P.set(P.string), (x) => 1)
+          .with(P.set(P.number), (x) => 2)
           .exhaustive()
       ).toEqual(1);
     });
@@ -467,21 +467,21 @@ describe('exhaustive()', () => {
 
       expect(
         match(input)
-          .with(new Map([['hello' as const, P.number]]), (x) => x)
+          .with(P.map('hello', P.number), (x) => x)
           // @ts-expect-error
           .exhaustive()
       ).toEqual(input);
 
       expect(
         match(input)
-          .with(new Map([['hello' as const, 1 as const]]), (x) => x)
+          .with(P.map('hello', 1), (x) => x)
           // @ts-expect-error
           .exhaustive()
       ).toEqual(input);
 
       expect(
         match(input)
-          .with(new Map([['hello', 1 as const]]), (x) => x)
+          .with(P.map('hello', 1), (x) => x)
           // @ts-expect-error
           .exhaustive()
       ).toEqual(input);