Have String.charCodeAt return option<int>; add charCodeAtUnsafe (#7877)

* Have `String.charCodeAt` return `option<int>`; add `charCodeAtUnsafe`

* CHANGELOG

Author: cknitt

CHANGELOG.md

@@ -16,6 +16,7 @@
 
 - Fix return type of `String.charCodeAt`. https://github.com/rescript-lang/rescript/pull/7864
 - Remove support of JSX children spread. https://github.com/rescript-lang/rescript/pull/7869
+- Have `String.charCodeAt` return `option<int>`; add `String.charCodeAtUnsafe`. https://github.com/rescript-lang/rescript/pull/7877
 
 #### :eyeglasses: Spec Compliance
 

packages/@rescript/runtime/Stdlib_String.res

@@ -17,7 +17,15 @@ external compare: (string, string) => Stdlib_Ordering.t = "%compare"
 @get_index external getUnsafe: (string, int) => string = ""
 @send external charAt: (string, int) => string = "charAt"
 
-@send external charCodeAt: (string, int) => int = "charCodeAt"
+@send external charCodeAtUnsafe: (string, int) => int = "charCodeAt"
+
+@val @scope("Number") external isNaN: float => bool = "isNaN"
+@send external charCodeAt: (string, int) => float = "charCodeAt"
+let charCodeAt = (s, i) => {
+  let c = charCodeAt(s, i)
+  isNaN(c) ? None : Some(c->Stdlib_Int.fromFloat)
+}
+
 @send external codePointAt: (string, int) => option<int> = "codePointAt"
 
 @send external concat: (string, string) => string = "concat"

packages/@rescript/runtime/Stdlib_String.resi

@@ -213,19 +213,36 @@ external charAt: (string, int) => string = "charAt"
 `charCodeAt(str, index)` returns the character code at position `index` in
 string `str` the result is in the range 0-65535, unlike `codePointAt`, so it
 will not work correctly for characters with code points greater than or equal
-to 0x10000. The return type is `float` because this function returns NaN if
-`index` is less than zero or greater than the length of the string.
+to 0x10000.
 See [`String.charCodeAt`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/charCodeAt) on MDN.
 
 ## Examples
 
 ```rescript
-String.charCodeAt(`😺`, 0) == 0xd83d
+String.charCodeAt(`😺`, 0) == Some(0xd83d)
+String.charCodeAt("", 0) == None
+String.codePointAt(`😺`, 0) == Some(0x1f63a)
+```
+*/
+let charCodeAt: (string, int) => option<int>
+
+/**
+`charCodeAtUnsafe(str, index)` returns the character code at position `index` in
+string `str` the result is in the range 0-65535, unlike `codePointAt`, so it
+will not work correctly for characters with code points greater than or equal
+to 0x10000.
+Beware: If the index is out of range, it will return `NaN` which is not actually a valid int.
+See [`String.charCodeAt`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/charCodeAt) on MDN.
+
+## Examples
+
+```rescript
+String.charCodeAtUnsafe(`😺`, 0) == 0xd83d
 String.codePointAt(`😺`, 0) == Some(0x1f63a)
 ```
 */
 @send
-external charCodeAt: (string, int) => int = "charCodeAt"
+external charCodeAtUnsafe: (string, int) => int = "charCodeAt"
 
 /**
 `codePointAt(str, index)` returns the code point at position `index` within

packages/@rescript/runtime/lib/es6/Stdlib_String.js

@@ -1,6 +1,15 @@
 
 
 
+function charCodeAt(s, i) {
+  let c = s.charCodeAt(i);
+  if (Number.isNaN(c)) {
+    return;
+  } else {
+    return c | 0;
+  }
+}
+
 function indexOfOpt(s, search) {
   let index = s.indexOf(search);
   if (index !== -1) {
@@ -38,6 +47,7 @@ function capitalize(s) {
 }
 
 export {
+  charCodeAt,
   indexOfOpt,
   lastIndexOfOpt,
   searchOpt,

packages/@rescript/runtime/lib/js/Stdlib_String.js

@@ -1,6 +1,15 @@
 'use strict';
 
 
+function charCodeAt(s, i) {
+  let c = s.charCodeAt(i);
+  if (Number.isNaN(c)) {
+    return;
+  } else {
+    return c | 0;
+  }
+}
+
 function indexOfOpt(s, search) {
   let index = s.indexOf(search);
   if (index !== -1) {
@@ -37,6 +46,7 @@ function capitalize(s) {
   }
 }
 
+exports.charCodeAt = charCodeAt;
 exports.indexOfOpt = indexOfOpt;
 exports.lastIndexOfOpt = lastIndexOfOpt;
 exports.searchOpt = searchOpt;