TS-Pattern v5 base branch

docs/roadmap.md

@@ -1,9 +1,30 @@
 ### Roadmap
 
-- [ ] Add a custom matcher protocol data structures could implement to make them matchable.
-- [ ] Add a native regex support.
-
-- [ ] (Maybe) add an iterator protocol to `P.array` to be usable as a variadic tuple pattern. Example of using `P.array`:
+- [ ] chainable methods
+  - [ ] string
+    - [x] `P.string.includes('str')`
+    - [x] `P.string.startsWith('str')`
+    - [x] `P.string.endsWith('str')`
+    - [ ] `P.string.regex('[a-z]+')`
+  - [ ] numbers
+    - [ ] `P.number.between(1, 10)`
+    - [ ] `P.number.lt(12)`
+    - [ ] `P.number.gt(12)`
+    - [ ] `P.number.gte(12)`
+    - [ ] `P.number.lte(12)`
+    - [ ] `P.number.int(12)`
+    - [ ] `P.number.finite`
+    - [ ] `P.number.positive`
+    - [ ] `P.number.negative`
+  - [ ] all
+    - [ ] `P.number.optional`
+    - [ ] `P.string.optional`
+    - [ ] `P.number.select()`
+    - [ ] `P.string.select()`
+    - [ ] `P.number.optional.select()`
+    - [ ] `P.string.optional.select()`
+- [x] Add a custom matcher protocol data structures could implement to make them matchable.
+- [x] (Maybe) add an iterator protocol to `P.array` to be usable as a variadic tuple pattern. Example of using `P.array`:
 
 ```ts
 const reverse = <T>(xs: T[]): T[] => {

docs/v4-to-v5-migration-guide.md

@@ -0,0 +1,235 @@
+# TS-Pattern v4 to v5 Migration Guide
+
+This file contains all breaking changes and new features between the version 4 and 5 of TS-Pattern.
+
+# Breaking changes
+
+## `.with` is now evaluated eagerly
+
+In the previous version of TS-Pattern, no code would execute until you called `.exhaustive()` or `.otherwise(...)`. For example, in the following code block, nothing would be logged to the console or thrown:
+
+```ts
+// TS-Pattern v4
+type Input = { type: 'ok'; value: number } | { type: 'error'; error: Error };
+
+// We don't call `.exhaustive`, so handlers don't run.
+function someFunction(input: Input) {
+  match(input)
+    .with({ type: 'ok' }, ({ value }) => {
+      console.log(value);
+    })
+    .with({ type: 'error' }, ({ error }) => {
+      throw error;
+    });
+}
+
+someFunction({ type: 'ok', value: 42 }); // nothing happens
+```
+
+In **TS-Pattern v5**, however, the library will execute the matching handler as soon as it finds it:
+
+```ts
+// TS-Pattern v5
+someFunction({ type: 'ok', value: 42 }); // logs "42" to the console!
+```
+
+Handlers are now evaluated **eagerly** instead of lazily. In practice, this shouldn't change anything as long as you always finish your pattern matching expressions by either `.exhaustive` or `.otherwise`.
+
+## Matching on Map and Sets
+
+Matching `Set` and `Map` instances using `.with(new Set(...))` and `.with(new Map(...))` is no longer supported. If you want to match specific sets and maps, you should now use the `P.map(keyPattern, valuePattern)` and `P.set(valuePattern)` patterns:
+
+```diff
+- import { match } from 'ts-pattern';
++ import { match, P } from 'ts-pattern';
+
+
+const someFunction = (value: Set<number> | Map<string, number>) =>
+  match(value)
+-   .with(new Set([P.number]), (set) => `a set of numbers`)
+-   .with(new Map([['key', P.number]]), (map) => `map.get('key') is a number`)
++   .with(P.set(P.number), (set) => `a set of numbers`)
++   .with(P.map('key', P.number), (map) => `map.get('key') is a number`)
+    .otherwise(() => null);
+```
+
+- The subpattern we provide in `P.set(subpattern)` should match all values in the set.
+- The value subpattern we provide in `P.map(keyPattern, subpattern)` should only match the values matching `keyPattern` for the whole `P.map(..)` pattern to match the input.
+
+# New features
+
+## chainable methods
+
+TS-Pattern v5's major addition is the ability to chain methods to narrow down the values matched by primitive patterns, like `P.string` or `P.number`.
+
+Since a few examples is worth a thousand words, here are a few ways you can use chainable methods:
+
+### P.number methods
+
+```ts
+const example = (position: { x: number; y: number }) =>
+  match(position)
+    .with({ x: P.number.gte(100) }, (value) => '🎮')
+    .with({ x: P.number.between(0, 100) }, (value) => '🎮')
+    .with(
+      {
+        x: P.number.positive().int(),
+        y: P.number.positive().int(),
+      },
+      (value) => '🎮'
+    )
+    .otherwise(() => 'x or y is negative');
+```
+
+Here is the full list of number methods:
+
+- `P.number.between(min, max)`: matches numbers between `min` and `max`.
+- `P.number.lt(max)`: matches numbers smaller than `max`.
+- `P.number.gt(min)`: matches numbers greater than `min`.
+- `P.number.lte(max)`: matches numbers smaller than or equal to `max`.
+- `P.number.gte(min)`: matches numbers greater than or equal to `min`.
+- `P.number.int()`: matches integers.
+- `P.number.finite()`: matches all numbers except `Infinity` and `-Infinity`
+- `P.number.positive()`: matches positive numbers.
+- `P.number.negative()`: matches negative numbers.
+
+### P.string methods
+
+```ts
+const example = (query: string) =>
+  match(query)
+    .with(P.string.startsWith('SELECT'), (query) => `selection`)
+    .with(P.string.endsWith('FROM user'), (query) => `👯‍♂️`)
+    .with(P.string.includes('*'), () => 'contains a star')
+    // Methods can be chained:
+    .with(P.string.startsWith('SET').includes('*'), (query) => `🤯`)
+    .exhaustive();
+```
+
+Here is the full list of string methods:
+
+- `P.string.startsWith(str)`: matches strings that start with `str`.
+- `P.string.endsWith(str)`: matches strings that end with `str`.
+- `P.string.minLength(min)`: matches strings with at least `min` characters.
+- `P.string.maxLength(max)`: matches strings with at most `max` characters.
+- `P.string.includes(str)`: matches strings that contain `str`.
+- `P.string.regex(RegExp)`: matches strings if they match this regular expression.
+
+### Global methods
+
+Some methods are available for all primitive type patterns:
+
+- `P.{..}.optional()`: matches even if this property isn't present on the input object.
+- `P.{..}.select()`: injects the matched value into the handler function.
+- `P.{..}.and(pattern)`: matches if the current pattern **and** the provided pattern match.
+- `P.{..}.or(pattern)`: matches if either the current pattern **or** the provided pattern match.
+
+```ts
+const example = (value: unknown) =>
+  match(value)
+    .with(
+      {
+        username: P.string,
+        displayName: P.string.optional(),
+      },
+      () => `{ username:string, displayName?: string }`
+    )
+    .with(
+      {
+        title: P.string,
+        author: { username: P.string.select() },
+      },
+      (username) => `author.username is ${username}`
+    )
+    .with(
+      P.instanceOf(Error).and({ source: P.string }),
+      () => `Error & { source: string }`
+    )
+    .with(P.string.or(P.number), () => `string | number`)
+    .otherwise(() => null);
+```
+
+## Variadic tuple patterns
+
+With TS-Pattern, you are now able to create array (or more accurately tuple) pattern with a variable number of elements:
+
+```ts
+const example = (value: unknown) =>
+  match(value)
+    .with(
+      // non-empty list of strings
+      [P.string, ...P.array(P.string)],
+      (value) => `value: [string, ...string[]]`
+    )
+    .otherwise(() => null);
+```
+
+Array patterns that include a `...P.array` are called **variadic tuple patterns**. You may only have a single `...P.array`, but as many fixed-index patterns as you want:
+
+```ts
+const example = (value: unknown) =>
+  match(value)
+    .with(
+      [P.string, P.string, P.string, ...P.array(P.string)],
+      (value) => `value: [string, string, string, ...string[]]`
+    )
+    .with(
+      [P.string, P.string, ...P.array(P.string)],
+      (value) => `value: [string, string, ...string[]]`
+    )
+    .with([], (value) => `value: []`)
+    .otherwise(() => null);
+```
+
+Fixed-index patterns can also be set **after** the `...P.array` variadic, or on both sides!
+
+```ts
+const example = (value: unknown) =>
+  match(value)
+    .with(
+      [...P.array(P.number), P.string, P.number],
+      (value) => `value: [...number[], string, number]`
+    )
+    .with(
+      [P.boolean, ...P.array(P.string), P.number, P.symbol],
+      (value) => `value: [boolean, ...string[], number, symbol]`
+    )
+    .otherwise(() => null);
+```
+
+Lastly, argument of `P.array` is now optional, and will default to `P._`, which matches anything:
+
+```ts
+const example = (value: unknown) =>
+  match(value)
+    //                         👇
+    .with([P.string, ...P.array()], (value) => `value: [string, ...unknown[]]`)
+    .otherwise(() => null);
+```
+
+## `.returnType`
+
+In TS-Pattern v4, the only way to explicitly set the return type of your `match` expression is to set the two `<Input, Output>` type parameters of `match`:
+
+```ts
+// TS-Pattern v4
+match<
+  { isAdmin: boolean; plan: 'free' | 'paid' }, // input type
+  number // return type
+>({ isAdmin, plan })
+  .with({ isAdmin: true }, () => 123)
+  .with({ plan: 'free' }, () => 'Oops!');
+//                              ~~~~~~ ❌ not a number.
+```
+
+the main drawback is that you need to set the **_input type_** explicitly **_too_**, even though TypeScript should be able to infer it.
+
+In TS-Pattern v5, you can use the `.returnType<Type>()` method to only set the return type:
+
+```ts
+match({ isAdmin, plan })
+  .returnType<number>() // 👈 new
+  .with({ isAdmin: true }, () => 123)
+  .with({ plan: 'free' }, () => 'Oops!');
+//                              ~~~~~~ ❌ not a number.
+```

examples/one-file-demo.ts

@@ -1,3 +1,5 @@
+import { isMatching, match, P } from 'ts-pattern';
+
 /**
  * ### One file TS-Pattern demo.
  *
@@ -11,8 +13,6 @@
  *   `P.array`, `P.optional`, etc.
  */
 
-import { isMatching, match, P } from 'ts-pattern';
-
 /**************************************************
  * Use case 1: handling discriminated union types *
  **************************************************/
@@ -22,7 +22,7 @@ type Response =
   | { type: 'image'; data: { extension: 'gif' | 'jpg' | 'png'; src: string } }
   | { type: 'text'; data: string; tags: { name: string; id: number }[] };
 
-const exampleFunction1 = (input: Response): string =>
+const example1 = (input: Response): string =>
   match(input)
     // 1. Basic pattern with inference with a wildcard
     .with({ type: 'video', data: { format: 'mp4' } }, (video) => video.data.src)
@@ -57,7 +57,7 @@ type UserType = 'editor' | 'viewer';
 // Uncomment 'enterprise' to see exhaustive checking in action
 type OrgPlan = 'basic' | 'pro' | 'premium'; // | 'enterprise';
 
-const exampleFunction2 = (org: OrgPlan, user: UserType) =>
+const example2 = (org: OrgPlan, user: UserType) =>
   // 1. Checking several enums with tuples
   match([org, user] as const)
     .with(['basic', P._], () => `Please upgrade to unlock this feature!`)
@@ -72,8 +72,31 @@ const exampleFunction2 = (org: OrgPlan, user: UserType) =>
     // 3. complex exhaustive checking
     .exhaustive();
 
+/**************************************************
+ * Use case 3: Matching specific strings or numbers
+ **************************************************/
+
+const example3 = (queries: string[]) =>
+  match(queries)
+    .with(
+      [
+        P.string.startsWith('SELECT').endsWith('FROM user').select(),
+        ...P.array(),
+      ],
+      (firstQuery) => `${firstQuery}: 👨‍👩‍👧‍👦`
+    )
+    .with(P.array(), () => 'other queries')
+    .exhaustive();
+
+const example4 = (position: { x: number; y: number }) =>
+  match(position)
+    .with({ x: P.number.gte(100) }, (value) => '⏱️')
+    .with({ x: P.number.between(0, 100) }, (value) => '⏱️')
+    .with({ x: P.number.positive(), y: P.number.positive() }, (value) => '⏱️')
+    .otherwise(() => 'x or y is negative');
+
 /******************************************
- * Use case 3: Validation an API response *
+ * Use case 4: Validation an API response *
  ******************************************/
 
 const userPattern = {
@@ -87,15 +110,17 @@ const userPattern = {
 };
 
 const postPattern = {
-  title: P.string,
+  title: P.string.minLength(2).maxLength(255),
+  stars: P.number.int().between(0, 5),
   content: P.string,
-  likeCount: P.number,
   author: userPattern,
   // 2. arrays
   comments: P.array({
     author: userPattern,
     content: P.string,
   }),
+  // 3. tuples (a non-empty array in this case)
+  tags: [P.string, ...P.array(P.string)],
 };
 
 type Post = P.infer<typeof postPattern>;

examples/package.json

@@ -4,6 +4,6 @@
   "main": "one-file-demo.ts",
   "author": "gvergnaud",
   "dependencies": {
-    "ts-pattern": "^4.1.2"
+    "ts-pattern": "^5.0.0-rc.1"
   }
 }