create the settings folder on save when missing

found while smoke-testing the utils jar standalone: the PDE and the
unit tests both pre-create the settings folder, but a standalone
caller passing a new location would fail on the first save.

Author: diyaayay

app/utils/src/main/java/processing/utils/Preferences.java

@@ -324,6 +324,10 @@ static public void save() throws IOException {
     // prefs for the open sketch before init() has been called.
     if (preferencesFile != null) {
       File dir = preferencesFile.getParentFile();
+      // standalone callers may pass a settings folder that doesn't exist yet
+      if (!dir.exists() && !dir.mkdirs()) {
+        throw new IOException("Could not create " + dir);
+      }
       File preferencesTemp = File.createTempFile("preferences", ".txt", dir);
       if (!preferencesTemp.setWritable(true, false)) {
         throw new IOException("Could not set " + preferencesTemp + " writable");

app/utils/src/test/java/processing/utils/PreferencesTest.java

@@ -211,6 +211,20 @@ public void testSaveWritesSortedKeys() throws IOException {
     }
 
 
+    /**
+     * A settings folder that doesn't exist yet is created on first save,
+     * so standalone callers can point at any location.
+     */
+    @Test
+    public void testInitCreatesMissingSettingsFolder() throws IOException {
+        var missing = new File(settingsFolder, "nested/settings");
+        assertFalse(missing.exists());
+
+        Preferences.init(missing);
+        assertTrue(new File(missing, "preferences.txt").exists());
+    }
+
+
     /**
      * A 3.x sketchbook location is migrated to the 4.0 key on init,
      * and the migrated preference is written back out right away.