fix: empty array (YousefED#481)

Author: ryansteil

test/programs/array-empty/main.ts

@@ -0,0 +1 @@
+type MyEmptyArray = [];

test/programs/array-empty/schema.json

@@ -0,0 +1,7 @@
+{
+    "$schema": "http://json-schema.org/draft-07/schema#",
+    "type": "array",
+    "minItems": 0,
+    "maxItems": 0
+}
+

test/schema.test.ts

@@ -346,6 +346,7 @@ describe("schema", () => {
     describe("maps and arrays", () => {
         assertSchema("array-readonly", "MyReadOnlyArray");
         assertSchema("array-types", "MyArray");
+        assertSchema("array-empty", "MyEmptyArray");
         assertSchema("map-types", "MyObject");
         assertSchema("extra-properties", "MyObject");
     });

typescript-json-schema.ts

@@ -633,7 +633,9 @@ export class JsonSchemaGenerator {
             const elemTypes: ts.NodeArray<ts.TypeNode> = (propertyType as any).typeArguments;
             const fixedTypes = elemTypes.map((elType) => this.getTypeDefinition(elType as any));
             definition.type = "array";
-            definition.items = fixedTypes;
+            if (fixedTypes.length > 0) {
+                definition.items = fixedTypes;
+            }
             const targetTupleType = (propertyType as ts.TupleTypeReference).target;
             definition.minItems = targetTupleType.minLength;
             if (targetTupleType.hasRestElement) {