Skip library paths that do not exist

Add ClassProvider#fromPaths

Author: SizableShrimp

src/main/java/net/minecraftforge/fart/api/ClassProvider.java

@@ -49,6 +49,27 @@ public static Builder builder() {
         return new ClassProviderBuilderImpl();
     }
 
+    /**
+     * Creates a class provider which reads class data from the provided library paths.
+     * All queried class infos will be cached for subsequent queries.
+     * <p>
+     * The default supported library paths are ZIP files and directories.
+     * Each path will be walked for all class files and stored in order.
+     * Like a class path, entries added earlier take precedence over later entries with the same name.
+     *
+     * @param paths the paths to read from
+     * @see #builder()
+     */
+    static ClassProvider fromPaths(Path... paths) {
+        Builder builder = builder().shouldCacheAll(true);
+
+        for (Path path : paths) {
+            builder.addLibrary(path);
+        }
+
+        return builder.build();
+    }
+
     /**
      * Creates a class provider which reads class data from the default classloader that loaded this class.
      */

src/main/java/net/minecraftforge/fart/internal/ClassProviderBuilderImpl.java

@@ -48,10 +48,13 @@ public ClassProvider.Builder addLibrary(Path path) {
             Path libraryDir;
             if (Files.isDirectory(path)) {
                 libraryDir = path;
-            } else {
+            } else if (Files.isRegularFile(path)) {
                 FileSystem zipFs = FileSystems.newFileSystem(path, (ClassLoader) null);
                 this.fileSystems.add(zipFs);
                 libraryDir = zipFs.getPath("/");
+            } else {
+                // We can't load it (it doesn't exist)
+                return this;
             }
 
             try (Stream<Path> walker = Files.walk(libraryDir)) {