fix typing issue and add typing verification

Author: Jayson Harshbarger

.vscode/settings.json

@@ -14,6 +14,7 @@
     "Randomator",
     "Randomators",
     "strs",
+    "typedoc",
     "ucase",
     "uhexa",
     "Wolfowitz",

README.md

@@ -60,8 +60,7 @@ A more involved example is the `string` function which take several options and
 ```js
 const chars$ = chars({ pool: 'abc' });
 const length$ = integers({ min: 3, max: 13 });
-const string$ = strings({ chars: chars$, length: length$ });
-console.log(string$());  // Prints a string between three (3) and 13 characters (inclusive) of 'a', 'b' or 'c'.
+const string$ = strings({ chars: chars$, length: length$ }); // A randomator that generates string between three (3) and 13 characters (inclusive) of 'a', 'b' or 'c'.
 ```
 
 And operators:

package-lock.json

@@ -4,7 +4,7 @@
   "version": "3.0.0-1",
   "description": "composable random generators",
   "main": "build/main/index.js",
-  "typings": "build/main/index.d.ts",
+  "types": "build/main/index.d.ts",
   "module": "build/module/index.js",
   "repository": "https://github.com/Hypercubed/Randomator",
   "license": "MIT",
@@ -19,6 +19,7 @@
     "test": "run-s test:*",
     "test:lint": "eslint \"src/**/*.{js,ts}\" --ext .ts",
     "test:prettier": "prettier \"src/**/*.{ts,js,css,md}\" --check",
+    "test:tsd": "tsd && echo \"Types verified\"",
     "test:unit": "jest --coverage --no-cache",
     "watch:build": "tsc -p tsconfig.main.json -w",
     "watch:test": "jest --watch",
@@ -66,6 +67,7 @@
     "prettier": "^2.5.1",
     "ts-jest": "^27.1.3",
     "ts-node": "^10.4.0",
+    "tsd": "^0.19.1",
     "typedoc": "^0.22.11",
     "typescript": "^4.5.5"
   },
@@ -82,5 +84,8 @@
     "hooks": {
       "pre-push": "npm run check"
     }
-  }
+  },
+  "tsd": {
+		"directory": "src"
+	}
 }

package.json

@@ -0,0 +1,51 @@
+/* eslint-disable @typescript-eslint/ban-types */
+
+import { expectAssignable, expectNotType, expectType } from 'tsd';
+
+import { Randomator } from './randomator.js';
+
+// from a value
+const a$ = Randomator.from('a');
+expectAssignable<Function>(a$);
+expectAssignable<() => string>(a$);
+expectAssignable<Iterable<string>>(a$);
+expectType<Randomator<string>>(a$);
+expectType<string>(a$());
+
+const b$ = Randomator.from(5);
+expectType<number>(b$());
+
+// from a function
+const c$ = Randomator.from(() => 'c');
+expectType<string>(c$());
+
+const d$ = Randomator.from(() => 5);
+expectType<number>(d$());
+
+// constructor
+const e$ = new Randomator(() => Math.random());
+expectType<number>(e$());
+
+// M(M(a)) === M(a)
+const f$ = new Randomator(a$);
+expectType<string>(f$());
+
+const g$ = Randomator.from(f$);
+expectType<string>(g$());
+
+// map
+const h$ = e$.map(a => String(a));
+expectNotType<number>(h$());
+expectType<string>(h$());
+
+// chain
+const i = e$.chain(a => a + a);
+expectType<number>(i);
+
+// filter
+const j$ = e$.filter(a => a > 0.5);
+expectType<number>(j$());
+
+// toArray
+const k = e$.toArray(5);
+expectType<number[]>(k);

src/lib/randomator.test-d.ts

@@ -103,3 +103,7 @@ export class Randomator<T = unknown> extends Function implements Iterable<T> {
     return Array.from({ length }, () => this());
   }
 }
+
+export interface Randomator<T> {
+  (): T;
+}

src/lib/randomator.ts

@@ -8,5 +8,5 @@
     "noEmit": false
   },
   "include": ["src/**/*.ts"],
-  "exclude": ["src/**/*.spec.ts", "node_modules/**"]
+  "exclude": ["src/**/*.spec.ts", "src/**/*.test-d.ts", "node_modules/**"]
 }

tsconfig.main.json

@@ -8,5 +8,5 @@
     "noEmit": false
   },
   "include": ["src/**/*.ts"],
-  "exclude": ["src/**/*.spec.ts", "node_modules/**"]
+  "exclude": ["src/**/*.spec.ts", "src/**/*.test-d.ts", "node_modules/**"]
 }