Handle missing file metadata on zip files

- Return EPOCH if a zip entry's creation/modification/access time is
   missing.
 - If a BasicFileAttributes.*Time method returns null, use 0 as our
   time. This shouldn't happen, but is a good sanity check.

Fixes #371

src/main/java/dan200/computercraft/core/apis/FSAPI.java

@@ -23,6 +23,7 @@ import java.io.BufferedWriter;
 import java.nio.channels.ReadableByteChannel;
 import java.nio.channels.WritableByteChannel;
 import java.nio.file.attribute.BasicFileAttributes;
+import java.nio.file.attribute.FileTime;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.OptionalLong;
@@ -359,8 +360,8 @@ public class FSAPI implements ILuaAPI
                 {
                     BasicFileAttributes attributes = m_fileSystem.getAttributes( path );
                     Map<String, Object> result = new HashMap<>();
-                    result.put( "modification", attributes.lastModifiedTime().toMillis() );
-                    result.put( "created", attributes.creationTime().toMillis() );
+                    result.put( "modification", getFileTime( attributes.lastModifiedTime() ) );
+                    result.put( "created", getFileTime( attributes.creationTime() ) );
                     result.put( "size", attributes.isDirectory() ? 0 : attributes.size() );
                     result.put( "isDir", attributes.isDirectory() );
                     return new Object[] { result };
@@ -375,4 +376,9 @@ public class FSAPI implements ILuaAPI
                 return null;
         }
     }
+
+    private static long getFileTime( FileTime time )
+    {
+        return time == null ? 0 : time.toMillis();
+    }
 }

src/main/java/dan200/computercraft/core/filesystem/JarMount.java

@@ -25,6 +25,7 @@ import java.nio.channels.Channels;
 import java.nio.channels.ReadableByteChannel;
 import java.nio.file.attribute.BasicFileAttributes;
 import java.nio.file.attribute.FileTime;
+import java.time.Instant;
 import java.util.Enumeration;
 import java.util.HashMap;
 import java.util.List;
@@ -290,19 +291,20 @@ public class JarMount implements IMount
         @Override
         public FileTime lastModifiedTime()
         {
-            return entry.getLastModifiedTime();
+            return orEpoch( entry.getLastModifiedTime() );
         }
 
         @Override
         public FileTime lastAccessTime()
         {
-            return entry.getLastAccessTime();
+            return orEpoch( entry.getLastAccessTime() );
         }
 
         @Override
         public FileTime creationTime()
         {
-            return entry.getCreationTime();
+            FileTime time = entry.getCreationTime();
+            return time == null ? lastModifiedTime() : time;
         }
 
         @Override
@@ -340,5 +342,12 @@ public class JarMount implements IMount
         {
             return null;
         }
+
+        private static final FileTime EPOCH = FileTime.from( Instant.EPOCH );
+
+        private static FileTime orEpoch( FileTime time )
+        {
+            return time == null ? EPOCH : time;
+        }
     }
 }

src/test/java/dan200/computercraft/core/filesystem/JarMountTest.java

@@ -15,20 +15,24 @@ import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.charset.StandardCharsets;
+import java.nio.file.attribute.BasicFileAttributes;
+import java.nio.file.attribute.FileTime;
+import java.time.Instant;
+import java.time.temporal.ChronoUnit;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipOutputStream;
 
 import static org.junit.jupiter.api.Assertions.*;
 
-@SuppressWarnings( "deprecation" )
 public class JarMountTest
 {
     private static final File ZIP_FILE = new File( "test-files/jar-mount.zip" );
 
+    private static final FileTime MODIFY_TIME = FileTime.from( Instant.EPOCH.plus( 2, ChronoUnit.DAYS ) );
+
     @BeforeAll
     public static void before() throws IOException
     {
-        if( ZIP_FILE.exists() ) return;
         ZIP_FILE.getParentFile().mkdirs();
 
         try( ZipOutputStream stream = new ZipOutputStream( new FileOutputStream( ZIP_FILE ) ) )
@@ -36,7 +40,7 @@ public class JarMountTest
             stream.putNextEntry( new ZipEntry( "dir/" ) );
             stream.closeEntry();
 
-            stream.putNextEntry( new ZipEntry( "dir/file.lua" ) );
+            stream.putNextEntry( new ZipEntry( "dir/file.lua" ).setLastModifiedTime( MODIFY_TIME ) );
             stream.write( "print('testing')".getBytes( StandardCharsets.UTF_8 ) );
             stream.closeEntry();
         }
@@ -63,7 +67,7 @@ public class JarMountTest
     {
         IMount mount = new JarMount( ZIP_FILE, "dir/file.lua" );
         byte[] contents;
-        try( InputStream stream = mount.openForRead( "" ) )
+        try( @SuppressWarnings( "deprecation" ) InputStream stream = mount.openForRead( "" ) )
         {
             contents = ByteStreams.toByteArray( stream );
         }
@@ -76,11 +80,28 @@ public class JarMountTest
     {
         IMount mount = new JarMount( ZIP_FILE, "dir" );
         byte[] contents;
-        try( InputStream stream = mount.openForRead( "file.lua" ) )
+        try( @SuppressWarnings( "deprecation" ) InputStream stream = mount.openForRead( "file.lua" ) )
         {
             contents = ByteStreams.toByteArray( stream );
         }
 
         assertEquals( new String( contents, StandardCharsets.UTF_8 ), "print('testing')" );
     }
+
+    @Test
+    public void fileAttributes() throws IOException
+    {
+        BasicFileAttributes attributes = new JarMount( ZIP_FILE, "dir" ).getAttributes( "file.lua" );
+        assertFalse( attributes.isDirectory() );
+        assertEquals( "print('testing')".length(), attributes.size() );
+        assertEquals( MODIFY_TIME, attributes.lastModifiedTime() );
+    }
+
+    @Test
+    public void directoryAttributes() throws IOException
+    {
+        BasicFileAttributes attributes = new JarMount( ZIP_FILE, "dir" ).getAttributes( "" );
+        assertTrue( attributes.isDirectory() );
+        assertEquals( 0, attributes.size() );
+    }
 }