From accb3c69600a979420e662bb37eb37c1bcc26e8c Mon Sep 17 00:00:00 2001
From: harrygr <harry@bulb.co.uk>
Date: Sun, 26 Aug 2018 12:14:01 +0100
Subject: [PATCH] feat: Exclude valid fields in validation result

---
 src/index.spec.ts | 18 +++++++++++++++++-
 src/index.ts      |  7 +++----
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/src/index.spec.ts b/src/index.spec.ts
index 212e049..c857216 100644
--- a/src/index.spec.ts
+++ b/src/index.spec.ts
@@ -21,7 +21,7 @@ describe('Basic validator usage', () => {
     ).toEqual({})
   })
 
-  it('only returns a message for the first failing contrait for a field', () => {
+  it('only returns a message for the first failing constraint for a field', () => {
     const ageValidator = makeValidator({ age: [required, atLeast18] })
 
     expect(
@@ -51,4 +51,20 @@ describe('Basic validator usage', () => {
 
     expect(result).toEqual({ password: 'Should be equal' })
   })
+
+  it('does not include the keys of passing fields in the validation result', () => {
+    const personValidator = makeValidator({
+      name: [required],
+      age: [required],
+    })
+
+    const fields = {
+      name: 'Tim',
+      age: undefined,
+    }
+
+    const result = personValidator(fields)
+
+    expect(result).not.toHaveProperty('name')
+  })
 })
diff --git a/src/index.ts b/src/index.ts
index f2b757a..c2eb4d3 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -5,9 +5,8 @@ export type Constraint<F extends object, T = any> = (
 export type Constraints<F extends object> = Partial<
   Record<keyof F, Constraint<F>[]>
 >
-export type ValidationResult<F extends object> = Record<
-  keyof F,
-  string | undefined
+export type ValidationResult<F extends object> = Partial<
+  Record<keyof F, string | undefined>
 >
 
 export function makeValidator<F extends object>(constraints: Constraints<F>) {
@@ -29,7 +28,7 @@ export function makeValidator<F extends object>(constraints: Constraints<F>) {
         undefined,
       )
 
-      return Object.assign({}, acc, { [fieldName]: error })
+      return error ? Object.assign({}, acc, { [fieldName]: error }) : acc
     }
 
     return fieldNames.reduce(getErrors, {} as ValidationResult<F>)