Fix #193: Add place to start 'pre-flight' checks (#214)

* Add a module where we can run tests for invariants for the application

* Fix 193: Add pre-flight checks

* Fix build

src/editor/bin/Oni2.re

@@ -40,6 +40,8 @@ let init = app => {
   let cliOptions = Core.Cli.parse(setup);
   Sys.chdir(cliOptions.folder);
 
+  PreflightChecks.run();
+
   let currentState = ref(Model.State.create());
 
   let onStateChanged = v => {

src/editor/bin/PreflightChecks.re

@@ -0,0 +1,17 @@
+/*
+ * PreflightChecks.re
+ *
+ * This establishes and verifies a set of invariants to ensure the environment
+ * is set up correctly for the application to run.
+ */
+
+open Oni_Core;
+
+let checkHomeDirectoryOrThrow = () => {
+  let _ = Filesystem.unsafeFindHome();
+  ();
+};
+
+let run = () => {
+  checkHomeDirectoryOrThrow();
+};