Add tests for using file operations on directories

lib/std/fs.zig

@@ -1110,10 +1110,18 @@ pub const Dir = struct {
     /// Delete a file name and possibly the file it refers to, based on an open directory handle.
     /// Asserts that the path parameter has no null bytes.
     pub fn deleteFile(self: Dir, sub_path: []const u8) DeleteFileError!void {
-        os.unlinkat(self.fd, sub_path, 0) catch |err| switch (err) {
-            error.DirNotEmpty => unreachable, // not passing AT_REMOVEDIR
-            else => |e| return e,
-        };
+        if (builtin.os.tag == .windows) {
+            const sub_path_w = try os.windows.sliceToPrefixedFileW(sub_path);
+            return self.deleteFileW(sub_path_w.span().ptr);
+        } else if (builtin.os.tag == .wasi) {
+            os.unlinkatWasi(self.fd, sub_path, 0) catch |err| switch (err) {
+                error.DirNotEmpty => unreachable, // not passing AT_REMOVEDIR
+                else => |e| return e,
+            };
+        } else {
+            const sub_path_c = try os.toPosixPath(sub_path);
+            return self.deleteFileZ(&sub_path_c);
+        }
     }
 
     pub const deleteFileC = @compileError("deprecated: renamed to deleteFileZ");
@@ -1122,6 +1130,17 @@ pub const Dir = struct {
     pub fn deleteFileZ(self: Dir, sub_path_c: [*:0]const u8) DeleteFileError!void {
         os.unlinkatZ(self.fd, sub_path_c, 0) catch |err| switch (err) {
             error.DirNotEmpty => unreachable, // not passing AT_REMOVEDIR
+            error.AccessDenied => |e| switch (builtin.os.tag) {
+                // non-Linux POSIX systems return EPERM when trying to delete a directory, so
+                // we need to handle that case specifically and translate the error
+                .macosx, .ios, .freebsd, .netbsd, .dragonfly => {
+                    // Don't follow symlinks to match unlinkat (which acts on symlinks rather than follows them)
+                    const fstat = os.fstatatZ(self.fd, sub_path_c, os.AT_SYMLINK_NOFOLLOW) catch return e;
+                    const is_dir = fstat.mode & os.S_IFMT == os.S_IFDIR;
+                    return if (is_dir) error.IsDir else e;
+                },
+                else => return e,
+            },
             else => |e| return e,
         };
     }

lib/std/fs/test.zig

@@ -73,6 +73,43 @@ test "directory operations on files" {
     file.close();
 }
 
+test "file operations on directories" {
+    var tmp_dir = tmpDir(.{});
+    defer tmp_dir.cleanup();
+
+    const test_dir_name = "test_dir";
+
+    try tmp_dir.dir.makeDir(test_dir_name);
+
+    testing.expectError(error.IsDir, tmp_dir.dir.createFile(test_dir_name, .{}));
+    testing.expectError(error.IsDir, tmp_dir.dir.deleteFile(test_dir_name));
+    // Currently, WASI will return error.Unexpected (via ENOTCAPABLE) when attempting fd_read on a directory handle.
+    // TODO: Re-enable on WASI once https://github.com/bytecodealliance/wasmtime/issues/1935 is resolved.
+    if (builtin.os.tag != .wasi) {
+        testing.expectError(error.IsDir, tmp_dir.dir.readFileAlloc(testing.allocator, test_dir_name, std.math.maxInt(usize)));
+    }
+    // Note: The `.write = true` is necessary to ensure the error occurs on all platforms.
+    // TODO: Add a read-only test as well, see https://github.com/ziglang/zig/issues/5732
+    testing.expectError(error.IsDir, tmp_dir.dir.openFile(test_dir_name, .{ .write = true }));
+
+    if (builtin.os.tag != .wasi) {
+        // TODO: use Dir's realpath function once that exists
+        const absolute_path = blk: {
+            const relative_path = try fs.path.join(testing.allocator, &[_][]const u8{ "zig-cache", "tmp", tmp_dir.sub_path[0..], test_dir_name });
+            defer testing.allocator.free(relative_path);
+            break :blk try fs.realpathAlloc(testing.allocator, relative_path);
+        };
+        defer testing.allocator.free(absolute_path);
+
+        testing.expectError(error.IsDir, fs.createFileAbsolute(absolute_path, .{}));
+        testing.expectError(error.IsDir, fs.deleteFileAbsolute(absolute_path));
+    }
+
+    // ensure the directory still exists as a sanity check
+    var dir = try tmp_dir.dir.openDir(test_dir_name, .{});
+    dir.close();
+}
+
 test "openSelfExe" {
     if (builtin.os.tag == .wasi) return error.SkipZigTest;