fix: handle spread elements in array initializers

packages/openapi-generator/src/codec.ts

@@ -188,7 +188,31 @@ function parseArrayExpression(
     if (E.isLeft(valueE)) {
       return valueE;
     }
-    result.push(valueE.right);
+    // swc sometimes sets this to `null` even though it is supposed to be `undefined`
+    if (element.spread) {
+      let init = valueE.right;
+      if (init.type === 'ref') {
+        const realInitE = findSymbolInitializer(project, source, init.name);
+        if (E.isLeft(realInitE)) {
+          return realInitE;
+        }
+        const schemaE = parsePlainInitializer(
+          project,
+          realInitE.right[0],
+          realInitE.right[1],
+        );
+        if (E.isLeft(schemaE)) {
+          return schemaE;
+        }
+        init = schemaE.right;
+      }
+      if (init.type !== 'tuple') {
+        return E.left('Spread element must be array literal');
+      }
+      result.push(...init.schemas);
+    } else {
+      result.push(valueE.right);
+    }
   }
   return E.right({ type: 'tuple', schemas: result });
 }

packages/openapi-generator/test/codec.test.ts

@@ -227,6 +227,44 @@ testCase('union type is parsed', UNION, {
   },
 });
 
+const UNION_SPREAD = `
+import * as t from 'io-ts';
+
+const common = [t.string];
+
+export const FOO = t.union([...common, t.number]);
+`;
+
+testCase('union type with spread is parsed', UNION_SPREAD, {
+  FOO: {
+    type: 'union',
+    schemas: [
+      { type: 'primitive', value: 'string' },
+      { type: 'primitive', value: 'number' },
+    ],
+  },
+  common: {
+    type: 'tuple',
+    schemas: [{ type: 'primitive', value: 'string' }],
+  },
+});
+
+const UNION_INLINE_SPREAD = `
+import * as t from 'io-ts';
+
+export const FOO = t.union([...[t.string], t.number]);
+`;
+
+testCase('union type with inline spread is parsed', UNION_INLINE_SPREAD, {
+  FOO: {
+    type: 'union',
+    schemas: [
+      { type: 'primitive', value: 'string' },
+      { type: 'primitive', value: 'number' },
+    ],
+  },
+});
+
 const INTERSECTION = `
 import * as t from 'io-ts';
 export const FOO = t.intersection([t.type({ foo: t.number }), t.partial({ bar: t.string })]);