Fix(@inquirer/expand): [Typescript] Enforce valid keys

Author: SBoudrias

packages/expand/README.md

@@ -86,13 +86,31 @@ const answer = await expand({
 
 ## Options
 
-| Property | Type                                                   | Required | Description                                                                               |
-| -------- | ------------------------------------------------------ | -------- | ----------------------------------------------------------------------------------------- |
-| message  | `string`                                               | yes      | The question to ask                                                                       |
-| choices  | `Array<{ key: string, name: string, value?: string }>` | yes      | Array of the different allowed choices. The `h`/help option is always provided by default |
-| default  | `string`                                               | no       | Default choices to be selected. (value must be one of the choices `key`)                  |
-| expanded | `boolean`                                              | no       | Expand the choices by default                                                             |
-| theme    | [See Theming](#Theming)                                | no       | Customize look of the prompt.                                                             |
+| Property | Type                    | Required | Description                                                                               |
+| -------- | ----------------------- | -------- | ----------------------------------------------------------------------------------------- |
+| message  | `string`                | yes      | The question to ask                                                                       |
+| choices  | `Choice[]`              | yes      | Array of the different allowed choices. The `h`/help option is always provided by default |
+| default  | `string`                | no       | Default choices to be selected. (value must be one of the choices `key`)                  |
+| expanded | `boolean`               | no       | Expand the choices by default                                                             |
+| theme    | [See Theming](#Theming) | no       | Customize look of the prompt.                                                             |
+
+### `Choice` object
+
+The `Choice` object is typed as
+
+```ts
+type Choice<Value> = {
+  value: Value;
+  name?: string;
+  key: string;
+};
+```
+
+Here's each property:
+
+- `value`: The value is what will be returned by `await expand()`.
+- `name`: The string displayed in the choice list. It'll default to the stringify `value`.
+- `key`: The input the use must provide to select the choice. Must be a lowercase single alpha-numeric character string.
 
 ## Theming
 

packages/expand/expand.test.mts

@@ -4,22 +4,22 @@ import expand from './src/index.mjs';
 
 const overwriteChoices = [
   {
-    key: 'y',
+    key: 'y' as const,
     name: 'Overwrite',
     value: 'overwrite',
   },
   {
-    key: 'a',
+    key: 'a' as const,
     name: 'Overwrite this one and all next',
     value: 'overwrite_all',
   },
   {
-    key: 'd',
+    key: 'd' as const,
     name: 'Show diff',
     value: 'diff',
   },
   {
-    key: 'x',
+    key: 'x' as const,
     name: 'Abort',
     value: 'abort',
   },

packages/expand/src/index.mts

@@ -11,39 +11,77 @@ import {
 import type { PartialDeep } from '@inquirer/type';
 import colors from 'yoctocolors-cjs';
 
+type Key =
+  | 'a'
+  | 'b'
+  | 'c'
+  | 'd'
+  | 'e'
+  | 'f'
+  | 'g'
+  // | 'h' // Help is excluded since it's a reserved key
+  | 'i'
+  | 'j'
+  | 'k'
+  | 'l'
+  | 'm'
+  | 'n'
+  | 'o'
+  | 'p'
+  | 'q'
+  | 'r'
+  | 's'
+  | 't'
+  | 'u'
+  | 'v'
+  | 'w'
+  | 'x'
+  | 'y'
+  | 'z'
+  | '0'
+  | '1'
+  | '2'
+  | '3'
+  | '4'
+  | '5'
+  | '6'
+  | '7'
+  | '8'
+  | '9';
+
 type Choice<Value> =
-  | { key: string; value: Value }
-  | { key: string; name: string; value: Value };
+  | { key: Key; value: Value }
+  | { key: Key; name: string; value: Value };
 
 type NormalizedChoice<Value> = {
   value: Value;
   name: string;
-  key: string;
+  key: Key;
 };
 
 type ExpandConfig<
   Value,
-  ChoicesObject = readonly { key: string; name: string }[] | readonly Choice<Value>[],
+  ChoicesObject = readonly { key: Key; name: string }[] | readonly Choice<Value>[],
 > = {
   message: string;
-  choices: ChoicesObject extends readonly { key: string; name: string }[]
+  choices: ChoicesObject extends readonly { key: Key; name: string }[]
     ? ChoicesObject
     : readonly Choice<Value>[];
-  default?: string;
+  default?: Key | 'h';
   expanded?: boolean;
   theme?: PartialDeep<Theme>;
 };
 
 function normalizeChoices<Value>(
-  choices: readonly { key: string; name: string }[] | readonly Choice<Value>[],
+  choices: readonly { key: Key; name: string }[] | readonly Choice<Value>[],
 ): NormalizedChoice<Value>[] {
   return choices.map((choice) => {
     const name: string = 'name' in choice ? choice.name : String(choice.value);
     const value = 'value' in choice ? choice.value : name;
     return {
       value: value as Value,
       name,
-      key: choice.key.toLowerCase(),
+      key: choice.key.toLowerCase() as Key,
     };
   });
 }