Array.fromOption with tests and docs

src/Core__Array.mjs

@@ -138,6 +138,14 @@ function findMap(arr, f) {
   };
 }
 
+function fromOption(opt) {
+  if (opt !== undefined) {
+    return Array.of(Caml_option.valFromOption(opt));
+  } else {
+    return Array.of();
+  }
+}
+
 export {
   make ,
   fromInitializer ,
@@ -155,5 +163,6 @@ export {
   shuffle ,
   shuffleInPlace ,
   findMap ,
+  fromOption ,
 }
 /* No side effect */

src/Core__Array.res

@@ -214,3 +214,12 @@ let findMap = (arr, f) => {
 }
 
 @send external at: (array<'a>, int) => option<'a> = "at"
+
+@val external of0: unit => array<'a> = "Array.of"
+@val external of1: 'a => array<'a> = "Array.of"
+
+let fromOption = opt =>
+  switch opt {
+  | None => of0()
+  | Some(a) => of1(a)
+  }

src/Core__Array.resi

@@ -955,3 +955,16 @@ let findMap: (array<'a>, 'a => option<'b>) => option<'b>
 */
 @send
 external at: (array<'a>, int) => option<'a> = "at"
+
+/**
+`fromOption` creates an empty array if the option is `None`, or creates an array of length 1 if the option is `Some`.
+
+## Examples
+
+```rescript
+Some(3)->Array.fromOption // [3]
+None->Array.fromOption // []
+Some([1,2,3])->Array.fromOption // [[1,2,3]]
+```
+*/
+let fromOption: option<'a> => array<'a>

test/ArrayTests.mjs

@@ -3,6 +3,7 @@
 import * as Test from "./Test.mjs";
 import * as Caml_obj from "rescript/lib/es6/caml_obj.js";
 import * as Core__List from "../src/Core__List.mjs";
+import * as Caml_option from "rescript/lib/es6/caml_option.js";
 import * as Core__Array from "../src/Core__Array.mjs";
 
 var eq = Caml_obj.equal;
@@ -401,7 +402,44 @@ Test.run([
 
           })), eq, undefined);
 
+function fromOptionTest(wrap, title) {
+  Test.run([
+        [
+          "ArrayTests.res",
+          103,
+          22,
+          45
+        ],
+        "fromOption : " + title + ""
+      ], Core__Array.fromOption(Caml_option.some(wrap)), eq, [wrap]);
+}
+
+fromOptionTest(3, "int");
+
+fromOptionTest("abc", "string");
+
+fromOptionTest(undefined, "undefined");
+
+fromOptionTest([
+      1,
+      2,
+      3
+    ], "array");
+
+fromOptionTest([], "empty array");
+
+Test.run([
+      [
+        "ArrayTests.res",
+        111,
+        20,
+        42
+      ],
+      "fromOption : if none"
+    ], Core__Array.fromOption(undefined), eq, []);
+
 export {
   eq ,
+  fromOptionTest ,
 }
 /*  Not a pure module */

test/ArrayTests.res

@@ -98,3 +98,14 @@ Test.run(
   eq,
   None,
 )
+
+let fromOptionTest = (wrap, title) =>
+  Test.run(__POS_OF__(`fromOption : ${title}`), Some(wrap)->Array.fromOption, eq, [wrap])
+
+3->fromOptionTest("int")
+"abc"->fromOptionTest("string")
+undefined->fromOptionTest("undefined")
+[1, 2, 3]->fromOptionTest("array")
+[]->fromOptionTest("empty array")
+
+Test.run(__POS_OF__("fromOption : if none"), None->Array.fromOption, eq, [])

test/TestSuite.mjs

@@ -26,6 +26,8 @@ var Concurrently = PromiseTest.Concurrently;
 
 var panicTest = ErrorTests.panicTest;
 
+var fromOptionTest = ArrayTests.fromOptionTest;
+
 var eq = IntTests.eq;
 
 var $$catch = IntTests.$$catch;
@@ -41,6 +43,7 @@ export {
   Catching ,
   Concurrently ,
   panicTest ,
+  fromOptionTest ,
   eq ,
   $$catch ,
 }