Some further improvemnets to mount error handling

- Correctly handle FileOperationExceptions for the root mount.
 - Remove some checks from MountWrapper: Mount/WritableMount should do
   these already!
 - Normalise file paths, always using a '/'.

projects/core-api/src/main/java/dan200/computercraft/api/filesystem/WritableMount.java

@@ -32,7 +32,8 @@ public interface WritableMount extends Mount {
     void makeDirectory(String path) throws IOException;
 
     /**
-     * Deletes a directory at a given path inside the virtual file system.
+     * Deletes a directory at a given path inside the virtual file system. If the file does not exist, this method
+     * should do nothing.
      *
      * @param path A file path in normalised format, relative to the mount location. ie: "programs/myoldprograms".
      * @throws IOException If the file does not exist or could not be deleted.

projects/core/src/main/java/dan200/computercraft/core/filesystem/FileMount.java

@@ -5,6 +5,7 @@
  */
 package dan200.computercraft.core.filesystem;
 
+import com.google.common.base.Joiner;
 import dan200.computercraft.api.filesystem.FileAttributes;
 import dan200.computercraft.api.filesystem.FileOperationException;
 import dan200.computercraft.api.filesystem.Mount;
@@ -104,7 +105,7 @@ public SeekableByteChannel openForRead(String path) throws FileOperationExceptio
     protected FileOperationException remapException(String fallbackPath, IOException exn) {
         return exn instanceof FileSystemException fsExn
             ? remapException(fallbackPath, fsExn)
-            : new FileOperationException(fallbackPath, exn.getMessage() == null ? "Operation failed" : exn.getMessage());
+            : new FileOperationException(fallbackPath, exn.getMessage() == null ? "Access denied" : exn.getMessage());
     }
 
     /**
@@ -123,7 +124,7 @@ protected FileOperationException remapException(String fallbackPath, FileSystemE
 
         var failedPath = Path.of(failedFile);
         return failedPath.startsWith(root)
-            ? new FileOperationException(root.relativize(failedPath).toString(), reason)
+            ? new FileOperationException(Joiner.on('/').join(root.relativize(failedPath)), reason)
             : new FileOperationException(fallbackPath, reason);
     }
 

projects/core/src/main/java/dan200/computercraft/core/filesystem/MountWrapper.java

@@ -79,7 +79,7 @@ public boolean exists(String path) throws FileSystemException {
     public boolean isDirectory(String path) throws FileSystemException {
         path = toLocal(path);
         try {
-            return mount.exists(path) && mount.isDirectory(path);
+            return mount.isDirectory(path);
         } catch (IOException e) {
             throw localExceptionOf(path, e);
         }
@@ -101,8 +101,7 @@ public void list(String path, List<String> contents) throws FileSystemException
     public long getSize(String path) throws FileSystemException {
         path = toLocal(path);
         try {
-            if (!mount.exists(path)) throw localExceptionOf(path, "No such file");
+            return mount.getSize(path);
-            return mount.isDirectory(path) ? 0 : mount.getSize(path);
         } catch (IOException e) {
             throw localExceptionOf(path, e);
         }
@@ -111,7 +110,6 @@ public long getSize(String path) throws FileSystemException {
     public BasicFileAttributes getAttributes(String path) throws FileSystemException {
         path = toLocal(path);
         try {
-            if (!mount.exists(path)) throw localExceptionOf(path, "No such file");
             return mount.getAttributes(path);
         } catch (IOException e) {
             throw localExceptionOf(path, e);
@@ -121,11 +119,7 @@ public BasicFileAttributes getAttributes(String path) throws FileSystemException
     public SeekableByteChannel openForRead(String path) throws FileSystemException {
         path = toLocal(path);
         try {
-            if (mount.exists(path) && !mount.isDirectory(path)) {
+            return mount.openForRead(path);
-                return mount.openForRead(path);
-            } else {
-                throw localExceptionOf(path, "No such file");
-            }
         } catch (IOException e) {
             throw localExceptionOf(path, e);
         }
@@ -136,11 +130,7 @@ public void makeDirectory(String path) throws FileSystemException {
 
         path = toLocal(path);
         try {
-            if (mount.exists(path)) {
+            writableMount.makeDirectory(path);
-                if (!mount.isDirectory(path)) throw localExceptionOf(path, "File exists");
-            } else {
-                writableMount.makeDirectory(path);
-            }
         } catch (IOException e) {
             throw localExceptionOf(path, e);
         }
@@ -151,9 +141,7 @@ public void delete(String path) throws FileSystemException {
 
         path = toLocal(path);
         try {
-            if (mount.exists(path)) {
+            writableMount.delete(path);
-                writableMount.delete(path);
-            }
         } catch (IOException e) {
             throw localExceptionOf(path, e);
         }
@@ -224,8 +212,8 @@ private String toLocal(String path) {
         return FileSystem.toLocal(path, location);
     }
 
-    private FileSystemException localExceptionOf(@Nullable String localPath, IOException e) {
+    private FileSystemException localExceptionOf(String localPath, IOException e) {
-        if (!location.isEmpty() && e instanceof FileOperationException ex) {
+        if (e instanceof FileOperationException ex) {
             if (ex.getFilename() != null) return localExceptionOf(ex.getFilename(), FileSystemException.getMessage(ex));
         }
 
@@ -233,8 +221,8 @@ private FileSystemException localExceptionOf(@Nullable String localPath, IOExcep
             // This error will contain the absolute path, leaking information about where MC is installed. We drop that,
             // just taking the reason. We assume that the error refers to the input path.
             var message = ex.getReason();
-            if (message == null) message = "Failed";
+            if (message == null) message = "Access denied";
-            return localPath == null ? new FileSystemException(message) : localExceptionOf(localPath, message);
+            return localExceptionOf(localPath, message);
         }
 
         return FileSystemException.of(e);

projects/core/src/main/java/dan200/computercraft/core/filesystem/WritableFileMount.java

@@ -183,7 +183,7 @@ public SeekableByteChannel openForWrite(String path) throws FileOperationExcepti
     }
 
     @Override
-    public SeekableByteChannel openForAppend(String path) throws IOException {
+    public SeekableByteChannel openForAppend(String path) throws FileOperationException {
         create();
 
         var file = resolvePath(path);