From 07ac8e41c554e912deb9034e048a80fd28eea566 Mon Sep 17 00:00:00 2001
From: PiggyPiglet <noreply@piggypiglet.me>
Date: Sun, 3 Jan 2021 23:42:23 +0800
Subject: [PATCH] Fix contract violations & add null checks which should close
 #515

---
 .../manager/LocalExpansionManager.java         | 18 +++++++++++++-----
 .../me/clip/placeholderapi/util/FileUtil.java  |  7 ++++---
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/src/main/java/me/clip/placeholderapi/expansion/manager/LocalExpansionManager.java b/src/main/java/me/clip/placeholderapi/expansion/manager/LocalExpansionManager.java
index 5e2e0b3..18a4c2b 100644
--- a/src/main/java/me/clip/placeholderapi/expansion/manager/LocalExpansionManager.java
+++ b/src/main/java/me/clip/placeholderapi/expansion/manager/LocalExpansionManager.java
@@ -300,7 +300,10 @@ public final class LocalExpansionManager implements Listener {
         return;
       }
 
-      final long registered = classes.stream().map(this::register).filter(Optional::isPresent)
+      final long registered = classes.stream()
+          .filter(Objects::nonNull)
+          .map(this::register)
+          .filter(Optional::isPresent)
           .count();
 
       Msg.msg(sender,
@@ -321,11 +324,9 @@ public final class LocalExpansionManager implements Listener {
     }
   }
 
-
   @NotNull
-  public CompletableFuture<@NotNull List<@NotNull Class<? extends PlaceholderExpansion>>> findExpansionsOnDisk() {
+  public CompletableFuture<@NotNull List<@Nullable Class<? extends PlaceholderExpansion>>> findExpansionsOnDisk() {
     return Arrays.stream(folder.listFiles((dir, name) -> name.endsWith(".jar")))
-        .filter(Objects::nonNull)
         .map(this::findExpansionInFile)
         .collect(Futures.collector());
   }
@@ -335,7 +336,14 @@ public final class LocalExpansionManager implements Listener {
       @NotNull final File file) {
     return CompletableFuture.supplyAsync(() -> {
       try {
-        return FileUtil.findClass(file, PlaceholderExpansion.class);
+        final Class<? extends PlaceholderExpansion> expansionClass = FileUtil.findClass(file, PlaceholderExpansion.class);
+
+        if (expansionClass == null) {
+          plugin.getLogger().severe("Failed to load Expansion: " + file.getName() + ", as it does not have" +
+                  "an a class which extends PlaceholderExpansion.");
+        }
+
+        return expansionClass;
       } catch (final VerifyError ex) {
         plugin.getLogger().severe("Failed to load Expansion class " + file.getName() +
             " (Is a dependency missing?)");
diff --git a/src/main/java/me/clip/placeholderapi/util/FileUtil.java b/src/main/java/me/clip/placeholderapi/util/FileUtil.java
index 9741a0d..7e20de1 100644
--- a/src/main/java/me/clip/placeholderapi/util/FileUtil.java
+++ b/src/main/java/me/clip/placeholderapi/util/FileUtil.java
@@ -20,6 +20,9 @@
 
 package me.clip.placeholderapi.util;
 
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
 import java.io.File;
 import java.io.IOException;
 import java.net.URL;
@@ -28,8 +31,6 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.jar.JarEntry;
 import java.util.jar.JarInputStream;
-import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
 
 public class FileUtil {
 
@@ -51,7 +52,7 @@ public class FileUtil {
       JarEntry entry;
       while ((entry = stream.getNextJarEntry()) != null) {
         final String name = entry.getName();
-        if (name == null || name.isEmpty() || !name.endsWith(".class")) {
+        if (name.isEmpty() || !name.endsWith(".class")) {
           continue;
         }