[code review] mark path parameter as non-nullable

Author: asolntsev

src/main/java/net/datafaker/service/FakeValuesService.java

@@ -106,8 +106,9 @@ private FakeValuesInterface getCachedFakeValue(SingletonLocale locale) {
      * @param path   path to a file with YAML structure
      * @throws IllegalArgumentException in case of invalid path
      */
-    public void addPath(Locale locale, @Nullable Path path) {
+    public void addPath(Locale locale, Path path) {
         requireNonNull(locale);
+        //noinspection ConstantValue
         if (path == null || Files.notExists(path) || Files.isDirectory(path) || !Files.isReadable(path)) {
             throw new IllegalArgumentException("Path should be an existing readable file: \"%s\"".formatted(path));
         }

src/test/java/net/datafaker/providers/base/CustomFakerTest.java

@@ -70,15 +70,18 @@ public String bee() {
     }
 
     @Test
+    @SuppressWarnings("DataFlowIssue")
     void addNullExistingPath() {
         assertThatThrownBy(() -> new BaseFaker().addPath(Locale.ENGLISH, null))
-            .isInstanceOf(IllegalArgumentException.class);
+            .isInstanceOf(IllegalArgumentException.class)
+            .hasMessage("Path should be an existing readable file: \"null\"");
     }
 
     @Test
     void addNonExistingPath() {
         assertThatThrownBy(() -> new BaseFaker().addPath(Locale.ENGLISH, Paths.get("non-existing-file")))
-            .isInstanceOf(IllegalArgumentException.class);
+            .isInstanceOf(IllegalArgumentException.class)
+            .hasMessage("Path should be an existing readable file: \"non-existing-file\"");
     }
 
     @RepeatedTest(10)