More Option refactoring, and some tests

src/common/all_test.ts

@@ -3,7 +3,7 @@ import Buffer from './buffer.ts';
 import Document from './document.ts';
 import Editor from './editor.ts';
 import { highlightToColor, HighlightType } from './highlight.ts';
-import _Option, { None, Some } from './option.ts';
+import Option, { None, Some } from './option.ts';
 import Position from './position.ts';
 import Row from './row.ts';
 
@@ -417,7 +417,19 @@ const EditorTest = {
 // ----------------------------------------------------------------------------
 
 const OptionTest = {
-	// @TODO implement Option tests
+	'Option.from()': () => {
+		assertTrue(Option.from(null).isNone());
+		assertTrue(Option.from().isNone());
+		assertEquivalent(Option.from(undefined), None);
+
+		assertEquivalent(Option.from(Some('foo')), Some('foo'));
+		assertEquivalent(Some(Some('bar')), Some('bar'));
+	},
+	'.toString': () => {
+		assertEquals(Some({}).toString(), 'Some ({})');
+		assertEquals(Some([1, 2, 3]).toString(), 'Some ([1,2,3])');
+		assertEquals(None.toString(), 'None');
+	},
 };
 
 // ----------------------------------------------------------------------------

src/common/option.ts

@@ -7,8 +7,27 @@ enum OptionType {
 	None = 'None',
 }
 
+// ----------------------------------------------------------------------------
+// Typeguards to handle Some/None difference
+// ----------------------------------------------------------------------------
+
 const isOption = <T>(v: any): v is Option<T> => v instanceof Option;
 
+class OptionInnerNone<T> {
+	public type: OptionType = OptionType.None;
+}
+
+class OptionInnerSome<T> {
+	public type: OptionType = OptionType.Some;
+
+	constructor(public value: T) {}
+}
+
+type OptionInnerType<T> = OptionInnerNone<T> | OptionInnerSome<T>;
+
+const isSome = <T>(v: OptionInnerType<T>): v is OptionInnerSome<T> =>
+	'value' in v && v.type === OptionType.Some;
+
 /**
  * Rust-style optional type
  *
@@ -18,50 +37,41 @@ export class Option<T> {
 	/**
 	 * The placeholder for the 'None' value type
 	 */
-	private static _noneInstance: Option<any> = new Option();
+	private static _None: Option<any> = new Option(null);
 
 	/**
 	 * Is this a 'Some' or a 'None'?
 	 */
-	private optionType: OptionType;
+	private readonly inner: OptionInnerType<T>;
 
-	/**
-	 * The value for the 'Some' type
-	 */
-	private value?: T;
-
-	private constructor(v?: T | null) {
-		if (v !== undefined && v !== null) {
-			this.optionType = OptionType.Some;
-			this.value = v;
-		} else {
-			this.optionType = OptionType.None;
-			this.value = undefined;
-		}
+	private constructor(v?: T) {
+		this.inner = (v !== undefined && v !== null)
+			? new OptionInnerSome(v)
+			: new OptionInnerNone();
 	}
 
 	public static get None(): Option<any> {
-		return <Option<any>> Option._noneInstance;
+		return Option._None;
 	}
 
-	public static Some<X>(v: X): Option<X> {
-		return new Option(v);
+	public static Some<X>(v: any): Option<X> {
+		return Option.from(v);
 	}
 
-	public static from<X>(v: any): Option<X> {
+	public static from<X>(v?: any): Option<X> {
 		return (isOption(v)) ? Option.from(v.unwrap()) : new Option(v);
 	}
 
 	isSome(): boolean {
-		return this.optionType === OptionType.Some && this.value !== undefined;
+		return isSome(this.inner);
 	}
 
 	isNone(): boolean {
-		return this.optionType === OptionType.None;
+		return !this.isSome();
 	}
 
 	isSomeAnd(fn: (a: T) => boolean): boolean {
-		return this.isSome() ? fn(this.unwrap()) : false;
+		return isSome(this.inner) ? fn(this.inner.value) : false;
 	}
 
 	isNoneAnd(fn: () => boolean): boolean {
@@ -69,20 +79,20 @@ export class Option<T> {
 	}
 
 	map<U>(fn: (a: T) => U): Option<U> {
-		return this.isSome() ? new Option(fn(this.unwrap())) : Option._noneInstance;
+		return isSome(this.inner) ? Option.from(fn(this.inner.value)) : Option.None;
 	}
 
 	mapOr<U>(def: U, f: (a: T) => U): U {
-		return this.isSome() ? f(this.unwrap()) : def;
+		return isSome(this.inner) ? f(this.inner.value) : def;
 	}
 
 	mapOrElse<U>(def: () => U, f: (a: T) => U): U {
-		return this.isSome() ? f(this.unwrap()) : def();
+		return isSome(this.inner) ? f(this.inner.value) : def();
 	}
 
 	unwrap(): T | never {
-		if (this.isSome() && this.value !== undefined) {
-			return this.value;
+		if (isSome(this.inner)) {
+			return this.inner.value;
 		}
 
 		console.error('None.unwrap()');
@@ -90,19 +100,19 @@ export class Option<T> {
 	}
 
 	unwrapOr(def: T): T {
-		return this.isSome() ? this.unwrap() : def;
+		return isSome(this.inner) ? this.inner.value : def;
 	}
 
 	unwrapOrElse(f: () => T): T {
-		return this.isSome() ? this.unwrap() : f();
+		return isSome(this.inner) ? this.inner.value : f();
 	}
 
 	and<U>(optb: Option<U>): Option<U> {
-		return this.isSome() ? optb : Option._noneInstance;
+		return isSome(this.inner) ? optb : Option.None;
 	}
 
 	andThen<U>(f: (a: T) => Option<U>): Option<U> {
-		return this.isSome() ? f(this.unwrap()) : Option._noneInstance;
+		return isSome(this.inner) ? f(this.inner.value) : Option.None;
 	}
 
 	or(optb: Option<T>): Option<T> {
@@ -114,10 +124,10 @@ export class Option<T> {
 	}
 
 	toString(): string {
-		const innerValue = (this.value !== undefined)
-			? JSON.stringify(this.value)
+		const innerValue = (isSome(this.inner))
+			? JSON.stringify(this.inner.value)
 			: '';
-		const prefix = this.optionType.valueOf();
+		const prefix = this.inner.type.valueOf();
 
 		return (innerValue.length > 0) ? `${prefix} (${innerValue})` : prefix;
 	}