Add valid path check for xcode-select'd Xcode

Summary: We should also check that Xcode exists at the path that the user has `xcode-select`'d

Reviewed By: passy

Differential Revision: D34168672

fbshipit-source-id: dc7c36bcb2ad1cec99e6ebb4d531417e55402f01

desktop/doctor/src/index.tsx

@@ -16,6 +16,7 @@ import * as watchman from 'fb-watchman';
 import * as fs from 'fs';
 import * as path from 'path';
 import type {FlipperDoctor} from 'flipper-common';
+import * as fs_extra from 'fs-extra';
 
 export function getHealthchecks(): FlipperDoctor.Healthchecks {
   return {
@@ -188,6 +189,12 @@ export function getHealthchecks(): FlipperDoctor.Healthchecks {
                       message: `xcode-select has no Xcode selected, You can select it using command "sudo xcode-select -switch <path/to/>Xcode.app".`,
                     };
                   }
+                  if ((await fs_extra.pathExists(selectedXcode)) == false) {
+                    return {
+                      hasProblem: true,
+                      message: `xcode-select has path of ${selectedXcode}, however this path does not exist on disk. Run "sudo xcode-select --switch" with a valid Xcode.app path.`,
+                    };
+                  }
                   return {
                     hasProblem: false,
                     message: `xcode-select has path of ${selectedXcode}.`,