From e7bdc117ee851868345ff771b9879db8107a969b Mon Sep 17 00:00:00 2001
From: Joram van den Boezem <joram@vandenboezem.nl>
Date: Wed, 27 May 2020 22:15:18 +0000
Subject: [PATCH] feat: prefer choices

---
 examples/types.ts | 39 +++++++++++++++++++++++++++++++++------
 src/baseArg.ts    | 42 +++++++++++++++++++++++++++---------------
 2 files changed, 60 insertions(+), 21 deletions(-)

diff --git a/examples/types.ts b/examples/types.ts
index 614ae3af..086c9893 100644
--- a/examples/types.ts
+++ b/examples/types.ts
@@ -1,20 +1,47 @@
 import { program, command } from '../src'
 
+/**
+ * Keep in mind that argument/option types are not validated at runtime.
+ * For example, when providing a default value with type boolean, it can be set
+ * to a string value at runtime.
+ */
+
 const string = command('string')
-  .argument('arg', 'Required string argument')
-  .option('opt', 'Optional string option', { type: 'string' })
+  .argument('arg', { description: 'Required string argument' })
+  .option('opt', { description: 'Optional string option', type: 'string' })
   .action((args) => {
     console.log('Args are', args)
   })
 
-const choices = command('string')
-  .argument('arg', 'Required string argument')
-  .option('opt', 'Optional string option', { type: 'string' })
+const choices = command('choices')
+  .argument('arg', {
+    description: 'Argument with choices',
+    choices: ['foo', 'bar'] as const,
+  })
+  .option('opt', {
+    description: 'Option with choices',
+    choices: ['option1', 'option2'] as const,
+    default: 'option3',
+  })
   .action((args) => {
     console.log('Args are', args)
   })
 
+const defaultValues = command('default')
+  .argument('arg', {
+    description: 'Optional argument with default value',
+    default: 5,
+    optional: true,
+  })
+  .option('opt', { description: 'Default value', default: true })
+  .action((args) => {
+    console.log('Args are', args)
+  })
 
-const app = program().description('All argument and option types').add(string)
+const app = program()
+  .description('All argument and option types')
+  .add(string)
+  .add(choices)
+  .add(defaultValues)
 
 app.withHelp().runOrRepl()
diff --git a/src/baseArg.ts b/src/baseArg.ts
index 5c91cd26..b69fb73e 100644
--- a/src/baseArg.ts
+++ b/src/baseArg.ts
@@ -6,21 +6,33 @@ export interface BaseArgOptions {
   prompt?: true | string
 }
 
-export type InferArgType<
-  O extends Options | PositionalOptions,
-  D = unknown
-> = O extends {
-  variadic: true
-  type: 'number'
-} // Add support for numeric variadic arguments
-  ? Array<number>
-  : O extends {
-      variadic: true
-    } // Add support for string variadic arguments
-  ? Array<string>
-  : unknown extends InferredOptionType<O> // Allow default type
-  ? D
-  : InferredOptionType<O>
+export type InferArgType<O extends Options | PositionalOptions, F = unknown> =
+  /**
+   * Add support for numeric variadic arguments
+   */
+  O extends {
+    variadic: true
+    type: 'number'
+  }
+    ? Array<number>
+    : /**
+     * Add support for string variadic arguments
+     */
+    O extends {
+        variadic: true
+      }
+    ? Array<string>
+    : /**
+     * Prefer choices over default
+     */
+    O extends { choices: ReadonlyArray<infer C> }
+    ? C
+    : /**
+     * Allow fallback type
+     */
+    unknown extends InferredOptionType<O>
+    ? F
+    : InferredOptionType<O>
 
 export class BaseArg {
   protected name: string