feat: accept io-ts codecs as table field types

docs/3.results/4.table_changes.md

@@ -17,9 +17,25 @@ Field types describe the structure of each field:
 
 ```typescript
 type FieldType =
-  | string                          // Primitive type name (e.g., "string", "number")
-  | Array<FieldType>                // Array of a given type
-  | { [subfield: string]: FieldType }; // Nested object
+  | string                              // Primitive type name (e.g., "string", "number")
+  | Array<StringFieldType>              // Array of a given type
+  | { [subfield: string]: StringFieldType } // Nested object
+  | import("io-ts").Mixed;              // io-ts codec at the field root
+```
+
+A field can be described either with the string-token vocabulary (primitives, arrays, nested records) or with a single [io-ts](https://github.com/gcanti/io-ts) codec at the root of the field. Codecs are not mixed inside string-tree records — use io-ts combinators (`t.type`, `t.array`, …) to nest within a codec.
+
+```typescript
+import * as t from "io-ts";
+
+const Order = {
+  fields: {
+    id: "string",
+    status: t.union([t.literal("open"), t.literal("closed")]),
+    meta: t.type({ source: t.string, retries: t.number }),
+  },
+  indexes: {},
+};
 ```
 
 ## Define Tables in a Schema

package.json

@@ -72,6 +72,8 @@
     "@types/node": "^22.19.15",
     "@types/semver": "^7.7.1",
     "chai": "^4.5.0",
+    "fp-ts": "^2.16.0",
+    "io-ts": "^2.2.0",
     "mongodb-memory-server-core": "^11.0.1",
     "release-it": "^19.2.4",
     "release-it-changelogen": "^0.1.0",

src/schema.ts

@@ -18,10 +18,22 @@ export interface IndexDefinition {
   multi?: boolean;
 }
 
-export type FieldType =
+export type StringFieldType =
   | string
-  | Array<FieldType>
-  | { [subfield: string]: FieldType };
+  | Array<StringFieldType>
+  | { [subfield: string]: StringFieldType };
+
+interface IoTsCodec {
+  readonly _A: unknown;
+  readonly _O: unknown;
+  readonly _I: unknown;
+  readonly name: string;
+  is(u: unknown): boolean;
+  encode(a: never): unknown;
+  decode(i: unknown): unknown;
+}
+
+export type FieldType = StringFieldType | IoTsCodec;
 
 /**
  * Schema table definition

src/tests/datasets/codec_fields.ts

@@ -0,0 +1,16 @@
+import * as t from "io-ts";
+import type { SchemaDefinition } from "../../schema";
+
+export const definition: SchemaDefinition = {
+  orders: {
+    fields: {
+      id: "string",
+      status: t.union([t.literal("open"), t.literal("closed")]),
+      meta: t.type({ source: t.string, retries: t.number }),
+      tags: "string[]",
+    },
+    indexes: {
+      status: {},
+    },
+  },
+};