feat(nullable/map+flatMap): return value unchanged if null or undefined

Author: glennsl

src/Core__Nullable.mjs

@@ -30,10 +30,11 @@ function getExn(value) {
 }
 
 function map(value, f) {
-  if (!(value == null)) {
+  if (value == null) {
+    return value;
+  } else {
     return Curry._1(f, value);
   }
-  
 }
 
 function mapWithDefault(value, $$default, f) {
@@ -45,10 +46,11 @@ function mapWithDefault(value, $$default, f) {
 }
 
 function flatMap(value, f) {
-  if (!(value == null)) {
+  if (value == null) {
+    return value;
+  } else {
     return Curry._1(f, value);
   }
-  
 }
 
 export {

src/Core__Nullable.res

@@ -31,7 +31,7 @@ external getUnsafe: t<'a> => 'a = "%identity"
 let map = (value, f) =>
   switch value->toOption {
   | Some(x) => make(f(x))
-  | None => undefined
+  | None => Obj.magic(value)
   }
 
 let mapWithDefault = (value, default, f) =>
@@ -43,5 +43,5 @@ let mapWithDefault = (value, default, f) =>
 let flatMap = (value, f) =>
   switch value->toOption {
   | Some(x) => f(x)
-  | None => undefined
+  | None => Obj.magic(value)
   }

src/Core__Nullable.resi

@@ -132,7 +132,8 @@ Nullable.getUnsafe(Nullable.null) // Raises an error
 external getUnsafe: t<'a> => 'a = "%identity"
 
 /**
-`map(value, f)` returns `f(value)` if `value` is not `null` or `undefined`, otherwise `undefined`.
+`map(value, f)` returns `f(value)` if `value` is not `null` or `undefined`,
+otherwise returns `value` unchanged.
 
 ## Examples
 
@@ -144,7 +145,8 @@ Nullable.map(Nullable.undefined, x => x * x) // Nullable.undefined
 let map: (t<'a>, 'a => 'b) => t<'b>
 
 /**
-`mapWithDefault(value, default, f)` returns `f(value)` if `value` is not `null` or `undefined`, otherwise `default`.
+`mapWithDefault(value, default, f)` returns `f(value)` if `value` is not `null`
+or `undefined`, otherwise returns `default`.
 
 ## Examples
 
@@ -159,7 +161,8 @@ noneValue->Nullable.mapWithDefault(0, x => x + 5) // 0
 let mapWithDefault: (t<'a>, 'b, 'a => 'b) => 'b
 
 /**
-`flatMap(value, f)` returns `f(value)` if `value` is not `null` or `undefined`, otherwise `undefined`.
+`flatMap(value, f)` returns `f(value)` if `value` is not `null` or `undefined`,
+otherwise returns `value` unchanged.
 
 ## Examples