56 lines
1.8 KiB
TypeScript
56 lines
1.8 KiB
TypeScript
import { strict as assert } from "node:assert";
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import { test } from "node:test";
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import { expectTypeOf } from "expect-type";
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import { type Matcher, P, match } from "./index.ts";
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test("match returns a builder", () => {
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const builder = match("x");
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expectTypeOf(builder).toHaveProperty("with");
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expectTypeOf(builder).toHaveProperty("exhaustive");
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expectTypeOf(builder).toHaveProperty("otherwise");
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});
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test("P.literal narrows to its literal type", () => {
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const matcher = P.literal("yes");
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expectTypeOf(matcher).toMatchTypeOf<Matcher<"yes">>();
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assert.equal(matcher.matches("yes"), true);
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assert.equal(matcher.matches("no"), false);
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});
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test("P.type narrows to the typeof target", () => {
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const matcher = P.type<string>("string");
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expectTypeOf(matcher).toMatchTypeOf<Matcher<string>>();
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assert.equal(matcher.matches("hi"), true);
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assert.equal(matcher.matches(42), false);
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});
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test("exhaustive() returns the union of handler return types", () => {
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const result = match<"a" | "b">("a" as "a" | "b")
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.with(P.literal("a"), () => 1 as const)
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.with(P.literal("b"), () => "two" as const)
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.exhaustive();
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expectTypeOf(result).toEqualTypeOf<1 | "two">();
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assert.equal(result, 1);
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});
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test("otherwise() falls back when no case matches", () => {
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const result = match<"x" | "y" | "z">("z" as "x" | "y" | "z")
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.with(P.literal("x"), (v): string => `got ${v}`)
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.otherwise((v): string => `fallback ${v}`);
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assert.equal(result, "fallback z");
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});
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test("exhaustive throws when no case matches", () => {
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assert.throws(
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() =>
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match<"a" | "b" | "c">("c" as "a" | "b" | "c")
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.with(P.literal("a"), () => "A")
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.with(P.literal("b"), () => "B")
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.exhaustive(),
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/no matching case/,
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);
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});
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