feat: add Schemable implementation for fast-check in contrib

fast-check does some nice stuff with property based testing and we can implement
Schemable for the fast-check Arbitrary, allowing us to somewhat generate fake
data from a Schema. Not sure if the IntersectArbitrary is a mess or not but
we'll see.

contrib/fast-check.ts

@@ -0,0 +1,62 @@
+import type { Arbitrary, Random, Stream, Value } from "npm:[email protected]";
+import type {
+  IntersectSchemable,
+  LiteralSchemable,
+  Schemable,
+  TupleSchemable,
+} from "../schemable.ts";
+import type { Kind, Out } from "../kind.ts";
+
+import * as fc from "npm:[email protected]";
+export * from "npm:[email protected]";
+
+export interface KindArbitrary extends Kind {
+  readonly kind: Arbitrary<Out<this, 0>>;
+}
+
+export class IntersectArbitrary<U, V> extends fc.Arbitrary<U & V> {
+  constructor(private first: Arbitrary<U>, private second: Arbitrary<V>) {
+    super();
+  }
+
+  generate(mrng: Random, biasFactor: number | undefined): Value<U & V> {
+    const fst = this.first.generate(mrng, biasFactor);
+    const snd = this.second.generate(mrng, biasFactor);
+    return new fc.Value(
+      Object.assign({}, fst.value, snd.value),
+      mrng.nextInt(),
+    );
+  }
+
+  canShrinkWithoutContext(value: unknown): value is U & V {
+    return this.first.canShrinkWithoutContext(value) &&
+      this.second.canShrinkWithoutContext(value);
+  }
+
+  shrink(value: U & V, context: unknown): Stream<Value<U & V>> {
+    return fc.Stream.of(new fc.Value(value, context));
+  }
+}
+
+export const SchemableArbitrary: Schemable<KindArbitrary> = {
+  unknown: fc.anything,
+  string: fc.string,
+  number: fc.float,
+  boolean: fc.boolean,
+  literal: fc.constantFrom as LiteralSchemable<KindArbitrary>["literal"],
+  nullable: fc.option,
+  undefinable: fc.option,
+  record: <T>(arb: Arbitrary<T>) => fc.dictionary(fc.string(), arb),
+  array: fc.array,
+  tuple: fc.tuple as TupleSchemable<KindArbitrary>["tuple"],
+  struct: fc.record,
+  partial: (items) => fc.record(items, { requiredKeys: [] }),
+  intersect:
+    ((second) => (first) =>
+      new IntersectArbitrary(first, second)) as IntersectSchemable<
+        KindArbitrary
+      >["intersect"],
+  union: (second) => (first) => fc.oneof(first, second),
+
+  lazy: (_id, builder) => fc.memo(builder)(),
+};

examples/schema.ts

@@ -0,0 +1,76 @@
+import { schema } from "../schemable.ts";
+import { SchemableDecoder } from "../decoder.ts";
+import { print, SchemableJsonBuilder } from "../json_schema.ts";
+import { sample, SchemableArbitrary } from "../contrib/fast-check.ts";
+import { pipe } from "../fn.ts";
+
+const Vector = schema((s) => s.tuple(s.number(), s.number(), s.number()));
+
+const Asteroid = schema((s) =>
+  s.struct({
+    type: s.literal("asteroid"),
+    location: Vector(s),
+    mass: s.number(),
+  })
+);
+
+const Planet = schema((s) =>
+  s.struct({
+    type: s.literal("planet"),
+    location: Vector(s),
+    mass: s.number(),
+    population: s.number(),
+    habitable: s.boolean(),
+  })
+);
+
+const Rank = schema((s) =>
+  pipe(
+    s.literal("captain"),
+    s.union(s.literal("first mate")),
+    s.union(s.literal("officer")),
+    s.union(s.literal("ensign")),
+  )
+);
+
+const CrewMember = schema((s) =>
+  s.struct({
+    name: s.string(),
+    age: s.number(),
+    rank: Rank(s),
+    home: Planet(s),
+  })
+);
+
+const Ship = schema((s) =>
+  s.struct({
+    type: s.literal("ship"),
+    location: Vector(s),
+    mass: s.number(),
+    name: s.string(),
+    crew: s.array(CrewMember(s)),
+  })
+);
+
+const SpaceObject = schema((s) =>
+  pipe(Asteroid(s), s.union(Planet(s)), s.union(Ship(s)))
+);
+
+const decoder = SpaceObject(SchemableDecoder);
+const arbitrary = SpaceObject(SchemableArbitrary);
+const json_schema = print(SpaceObject(SchemableJsonBuilder));
+
+const rands = sample(arbitrary, 10);
+const checks = rands.map(decoder);
+
+console.log({ json_schema, rands, checks });
+
+const intersect = schema((s) =>
+  pipe(
+    s.struct({ one: s.number() }),
+    s.intersect(s.partial({ two: s.string() })),
+  )
+);
+
+const iarbitrary = intersect(SchemableArbitrary);
+console.log("Intersect", sample(iarbitrary, 20));

iterable.ts

@@ -18,7 +18,7 @@
  * @since 2.0.0
  */
 
-import type { $, Kind, Out } from "./kind.ts";
+import type { Kind, Out } from "./kind.ts";
 import type { Applicable } from "./applicable.ts";
 import type { Combinable } from "./combinable.ts";
 import type { Either } from "./either.ts";

testing/contrib/fast-check.test.ts

@@ -0,0 +1,93 @@
+import { assertEquals } from "https://deno.land/[email protected]/testing/asserts.ts";
+
+import * as F from "../../contrib/fast-check.ts";
+import * as R from "../../refinement.ts";
+import { schema } from "../../schemable.ts";
+import { pipe } from "../../fn.ts";
+
+Deno.test("Fast Check Schemable", () => {
+  const Vector = schema((s) => s.tuple(s.number(), s.number(), s.number()));
+
+  const Asteroid = schema((s) =>
+    s.struct({
+      type: s.literal("asteroid"),
+      location: Vector(s),
+      mass: s.number(),
+      tags: s.record(s.boolean()),
+    })
+  );
+
+  const Planet = schema((s) =>
+    s.struct({
+      type: s.literal("planet"),
+      location: Vector(s),
+      mass: s.number(),
+      population: s.number(),
+      habitable: s.boolean(),
+    })
+  );
+
+  const Rank = schema((s) =>
+    pipe(
+      s.literal("captain"),
+      s.union(s.literal("first mate")),
+      s.union(s.literal("officer")),
+      s.union(s.literal("ensign")),
+    )
+  );
+
+  const CrewMember = schema((s) =>
+    pipe(
+      s.struct({
+        name: s.string(),
+        age: s.number(),
+        rank: Rank(s),
+        home: Planet(s),
+      }),
+      s.intersect(s.partial({
+        tags: s.record(s.string()),
+      })),
+    )
+  );
+
+  const Ship = schema((s) =>
+    s.struct({
+      type: s.literal("ship"),
+      location: Vector(s),
+      mass: s.number(),
+      name: s.string(),
+      crew: s.array(CrewMember(s)),
+      lazy: s.lazy("lazy", () => s.string()),
+    })
+  );
+
+  const SpaceObject = schema((s) =>
+    pipe(Asteroid(s), s.union(Planet(s)), s.union(Ship(s)))
+  );
+
+  const refinement = SpaceObject(R.SchemableRefinement);
+  const arbitrary = SpaceObject(F.SchemableArbitrary);
+  const rands = F.sample(arbitrary, 10);
+
+  for (const rand of rands) {
+    assertEquals(refinement(rand), true);
+  }
+});
+
+Deno.test("Fast Check IntersectArbitrary", () => {
+  const intersect = new F.IntersectArbitrary(
+    F.record({ one: F.integer() }),
+    F.record({ two: F.string() }),
+  );
+
+  assertEquals(intersect.canShrinkWithoutContext(null), false);
+  assertEquals(
+    intersect.canShrinkWithoutContext({ one: 1, two: "two" }),
+    false,
+  );
+
+  assertEquals(
+    intersect.shrink({ one: 1, two: "two" }, null),
+    F.Stream.of(new F.Value({ one: 1, two: "two" }, 0)),
+  );
+});