From e277d00218667ebc9dcde898a1cadb9eea178792 Mon Sep 17 00:00:00 2001
From: Sam Verschueren <sam.verschueren@gmail.com>
Date: Fri, 11 Jan 2019 08:06:52 +0100
Subject: [PATCH] Only infer label when predicate fails - fixes #115

---
 source/index.ts                    | 11 ++++++++---
 source/lib/predicates/predicate.ts | 24 ++++++++++++++++--------
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/source/index.ts b/source/index.ts
index 024b4c0..bdcadc3 100644
--- a/source/index.ts
+++ b/source/index.ts
@@ -201,12 +201,15 @@ export interface Ow {
 	any(...predicate: BasePredicate[]): AnyPredicate;
 }
 
-const main = <T>(value: T, labelOrPredicate: BasePredicate<T> | string | undefined, predicate?: BasePredicate<T>) => {
+const main = <T>(value: T, labelOrPredicate: BasePredicate<T> | string | Function | undefined, predicate?: BasePredicate<T>) => {
 	let label: any = labelOrPredicate;
 	let testPredicate: any = predicate;
 
 	if (isPredicate(labelOrPredicate)) {
-		label = inferLabel(callsites());
+		const stackFrames = callsites();
+
+		// Pass in a label function to only infer it when it fails
+		label = () => inferLabel(stackFrames);
 		testPredicate = labelOrPredicate;
 	}
 
@@ -227,7 +230,9 @@ Object.defineProperties(main, {
 	create: {
 		value: <T>(labelOrPredicate: BasePredicate<T> | string | undefined, predicate?: BasePredicate<T>) => (value: T) => {
 			if (isPredicate(labelOrPredicate)) {
-				return main(value, inferLabel(callsites()), labelOrPredicate);
+				const stackFrames = callsites();
+
+				return main(value, () => inferLabel(stackFrames), labelOrPredicate);
 			}
 
 			return main(value, labelOrPredicate, predicate);
diff --git a/source/lib/predicates/predicate.ts b/source/lib/predicates/predicate.ts
index 2d1384b..0d31c46 100644
--- a/source/lib/predicates/predicate.ts
+++ b/source/lib/predicates/predicate.ts
@@ -55,18 +55,26 @@ export class Predicate<T = any> implements BasePredicate<T> {
 	 * @hidden
 	 */
 	// tslint:disable completed-docs
-	[testSymbol](value: T, main: Ow, label?: string) {
-		const label2 = label
-			? `${this.type} \`${label}\``
-			: this.type;
-
+	[testSymbol](value: T, main: Ow, label?: string | Function) {
 		for (const {validator, message} of this.context.validators) {
 			const result = validator(value);
 
-			if (typeof result !== 'boolean' || !result) {
-				// TODO: Modify the stack output to show the original `ow()` call instead of this `throw` statement
-				throw new ArgumentError(message(value, label2, result), main);
+			if (result === true) {
+				continue;
+			}
+
+			let label2 = label;
+
+			if (typeof label === 'function') {
+				label2 = label();
 			}
+
+			label2 = label2
+				? `${this.type} \`${label2}\``
+				: this.type;
+
+			// TODO: Modify the stack output to show the original `ow()` call instead of this `throw` statement
+			throw new ArgumentError(message(value, label2, result), main);
 		}
 	}