We can't run this for yarn on Windows because Crystal appends .exe to yarn which doesn't exist. There may be a way around it, but I don't have a way to test

Author: jwoertink

src/web_app_skeleton/script/system_check.cr.ecr

@@ -11,9 +11,14 @@ require "./helpers/*"
 #     should go in your Procfile.dev.
 
 <%- if browser? -%>
+{% if flag(:windows) %}
+# Crystal appends ".exe" to the end of the command when searching for an executable; however,
+# depending on how you installed yarn, there may not be a "yarn.exe" available causing this to fail
+{% else %}
 if command_not_found "yarn"
   print_error "Yarn is not installed\n  See https://yarnpkg.com/lang/en/docs/install/ for install instructions."
 end
+{% end %}
 <%- end -%>
 
 # CUSTOM PRE-BOOT CHECKS