Watch.zig: better account for resource cleanup

Author: jayrod246

lib/std/Build/Watch.zig

@@ -266,15 +266,20 @@ const Os = switch (builtin.os.tag) {
                 lpCompletionRoutine: windows.LPOVERLAPPED_COMPLETION_ROUTINE,
             ) callconv(windows.WINAPI) windows.BOOL;
 
-            fn readChanges(self: *@This()) void {
+            fn readChanges(self: *@This()) !void {
                 const notify_filter =
                     windows.FILE_NOTIFY_CHANGE_CREATION |
                     windows.FILE_NOTIFY_CHANGE_DIR_NAME |
                     windows.FILE_NOTIFY_CHANGE_FILE_NAME |
                     windows.FILE_NOTIFY_CHANGE_LAST_WRITE |
                     windows.FILE_NOTIFY_CHANGE_SIZE;
                 const r = ReadDirectoryChangesW(self.handle, @ptrCast(&self.buffer), self.buffer.len, 0, notify_filter, null, &self.overlapped, null);
-                assert(r != 0);
+                if (r == 0) {
+                    switch (windows.GetLastError()) {
+                        .INVALID_FUNCTION => return error.ReadDirectoryChangesUnsupported,
+                        else => |err| return windows.unexpectedError(err),
+                    }
+                }
             }
 
             fn getWaitHandle(self: @This()) windows.HANDLE {
@@ -340,7 +345,7 @@ const Os = switch (builtin.os.tag) {
                 offset += notify.NextEntryOffset;
             }
 
-            dir.readChanges();
+            try dir.readChanges();
             return any_dirty;
         }
 
@@ -408,18 +413,22 @@ const Os = switch (builtin.os.tag) {
                             // directory on the file system.
                             // In such case, we must revert adding this directory, but keep
                             // the additions to the step set.
-                            const dh_gop = try w.os.handle_table.getOrPut(gpa, dir_handle);
+                            const dh_gop = w.os.handle_table.getOrPut(gpa, dir_handle) catch |err| {
+                                windows.CloseHandle(dir_handle);
+                                return err;
+                            };
                             if (dh_gop.found_existing) {
                                 _ = w.dir_table.pop();
                             } else {
                                 assert(dh_gop.index == gop.index);
                                 dh_gop.value_ptr.* = .{};
                                 const dir = try Os.Directory.init(gpa, dir_handle);
+                                errdefer dir.deinit(gpa);
+                                try dir.readChanges();
                                 try w.os.handle_extra.insert(gpa, dh_gop.index, .{
                                     .dir = dir,
                                     .wait_handle = dir.getWaitHandle(),
                                 });
-                                dir.readChanges();
                             }
                             break :rs &w.os.handle_table.values()[dh_gop.index];
                         }