From 4d2279f74c361c45e27f461989a0b9e90b6d4d16 Mon Sep 17 00:00:00 2001
From: Nicolas Froidure <nicolas.froidure@gmail.com>
Date: Mon, 9 Oct 2023 14:09:43 +0200
Subject: [PATCH] feat(types): encode min length arrays into types

Allows to encode into produced types the minnimum length of arrays.
---
 src/index.test.ts | 27 +++++++++++++++++++++++++++
 src/index.ts      | 25 +++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/src/index.test.ts b/src/index.test.ts
index 110679d..0c203dc 100644
--- a/src/index.test.ts
+++ b/src/index.test.ts
@@ -1074,6 +1074,33 @@ describe('generateTypeDeclaration()', () => {
 `);
   });
 
+  test('should create tuples from min length arrays', async () => {
+    const schema: JSONSchema7 = {
+      title: 'FixedArrayToTupleTest',
+      type: 'object',
+      additionalProperties: false,
+      required: ['data'],
+      properties: {
+        data: {
+          type: 'array',
+          items: { type: 'string' },
+          minItems: 2,
+        },
+      },
+    };
+
+    expect(toSource(await generateTypeDeclaration(context, schema)))
+      .toMatchInlineSnapshot(`
+"export type FixedArrayToTupleTest = NonNullable<{
+    data: NonNullable<[
+        NonNullable<string>,
+        NonNullable<string>,
+        ...NonNullable<string>[]
+    ]>;
+}>;"
+`);
+  });
+
   test('should work with tuples and rest test case schemas', async () => {
     const schema: JSONSchema7 = {
       title: 'TupleTest',
diff --git a/src/index.ts b/src/index.ts
index 4286344..4b5d13f 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1312,6 +1312,31 @@ async function buildArrayTypeNode(
       );
     }
 
+    // Switch from arrays to tuples and spread for small min length arrays
+    if (
+      'minItems' in schema &&
+      typeof schema.minItems === 'number' &&
+      schema.minItems > 0 &&
+      schema.minItems <
+        context.jsonSchemaOptions.tuplesFromFixedArraysLengthLimit
+    ) {
+      return ts.factory.createTupleTypeNode(
+        new Array(schema.minItems)
+          .fill(
+            types.length > 1 ? ts.factory.createUnionTypeNode(types) : types[0],
+          )
+          .concat(
+            ts.factory.createRestTypeNode(
+              ts.factory.createArrayTypeNode(
+                types.length > 1
+                  ? ts.factory.createUnionTypeNode(types)
+                  : types[0],
+              ),
+            ),
+          ),
+      );
+    }
+
     return ts.factory.createArrayTypeNode(
       types.length > 1 ? ts.factory.createUnionTypeNode(types) : types[0],
     );