From 5fd40588188f24cc7ce5393d0c4515be5df87961 Mon Sep 17 00:00:00 2001
From: Florian <florian@tentwentyfour.lu>
Date: Mon, 11 Nov 2019 18:57:36 -0500
Subject: [PATCH] fix(Result): Result.recoverWhen should execute the predicate
 before executing the lambda

---
 source/result.js    |  5 +++--
 test/result-test.js | 17 +++++++++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/source/result.js b/source/result.js
index 6a0725d..99ba175 100644
--- a/source/result.js
+++ b/source/result.js
@@ -183,8 +183,9 @@ Object.assign(Error.prototype, {
 
   recoverWhen(predicate, λ) {
     return Ok(this.error)
-    .map(λ)
-    .filter(predicate);
+    .filter(predicate)
+    .mapError(constant(this.error))
+    .map(λ);
   },
 
   merge() {
diff --git a/test/result-test.js b/test/result-test.js
index f1c6c34..5da4feb 100644
--- a/test/result-test.js
+++ b/test/result-test.js
@@ -307,6 +307,23 @@ describe('The Result type', () => {
 
         expect(transformed.merge()).to.equal(value);
       });
+
+      it('should not call the lambda if the predicate evaluates to false', () => {
+        let lambdaCalled = false;
+
+        const value = 10;
+
+        const error = Error(value);
+
+        const transformed = error.recoverWhen(constant(false), () => {
+          lambdaCalled = true;
+        });
+
+        console.log(transformed);
+
+        expect(lambdaCalled).to.equal(false);
+        expect(transformed.merge()).to.equal(value);
+      });
     });
 
     describe('flatMap(λ)', () => {