Remove reduce in CompilerManagerHook promise chain

That promise chain could be simplified too though

Author: chenglou

src/common/CompilerManagerHook.mjs

@@ -105,11 +105,11 @@ function attachCompilerAndLibraries(version, libraries, param) {
                         })];
                 return Promise.all(tmp);
               }).then(function (all) {
-              var errors = Belt_Array.reduce(all, [], (function (acc, r) {
+              var errors = Belt_Array.keepMap(all, (function (r) {
                       if (r.TAG === /* Ok */0) {
-                        return acc;
+                        return ;
                       } else {
-                        return acc.concat([r._0]);
+                        return r._0;
                       }
                     }));
               if (errors.length !== 0) {

src/common/CompilerManagerHook.res

@@ -126,13 +126,12 @@ let attachCompilerAndLibraries = (~version: string, ~libraries: array<string>, (
     Promise.all(promises)
   })
   ->Promise.map(all => {
-    // all: array(Promise.result(unit, string))
-    let errors = Belt.Array.reduce(all, [], (acc, r) =>
+    let errors = Belt.Array.keepMap(all, r => {
       switch r {
-      | Error(msg) => Js.Array2.concat(acc, [msg])
-      | _ => acc
+      | Error(msg) => Some(msg)
+      | _ => None
       }
-    )
+    })
 
     switch errors {
     | [] => Ok()