Don't destroy buffer when underlying file is deleted.

[iolsen]

WIP toward fixing atom/tabs#306.

I actually feel the existing behavior is crazytown and the people complaining in the issue above are 100% right. IMHO there shouldn't even be an option to maintain this anti-social, silently destructive behavior. 😜

But I see there were actually quite a few people advocating for it in atom/tabs#160 so, fine. Option it is.

However I do feel strongly that reverting the default is The Right Thing because the current behavior can cause lost data in a totally unexpected way. So people who want their tabs silently closing, as they do now, will have to go change an option.

With this change a buffer whose underlying file has been deleted is essentially treated as a new, unsaved file:

• When opened in the scope of a project its state will be saved until it's explicitly saved to a real file.
• When opened without a project (in tandem with the fix in Fix for #10474 atom#12922) there will be a prompt to save or discard.
• When closing the tab there will be a prompt to save or discard.

Still TODO:

• Fix the explicit file delete command within Atom to close the buffer as it does before this change (Manually close editors for files deleted from tree view tree-view#1026)
• Add a setting to auto-close on delete (Add option for closing deleted file tabs atom#13657)
• Tests

[vjeux]

That would be super useful! @kyldvs made it work as an init.js script while this is getting merged in and released.

let updatedPrototype = false;
atom.workspace.observeTextEditors(function (editor) {
  if (updatedPrototype) {
    return;
  }

  const TextBuffer = editor.buffer.constructor;

  let inSubscribeToFile = false;
  const subscribeToFile = TextBuffer.prototype.subscribeToFile;
  TextBuffer.prototype.subscribeToFile = function () {
    inSubscribeToFile = true;
    const ret = subscribeToFile.apply(this, arguments);
    inSubscribeToFile = false;
    return ret;
  };

  const File = editor.buffer.file.constructor;

  let inOnDidDeleteCallback = false;
  const onDidDelete = File.prototype.onDidDelete;
  File.prototype.onDidDelete = function () {
    let fn = arguments[0]; // Should be a function.
    if (inSubscribeToFile) {
      const ogFn = fn;
      fn = function () {
        inOnDidDeleteCallback = true;
        const ret = ogFn.apply(this, arguments);
        inOnDidDeleteCallback = false;
        return ret;
      };
    }
    return onDidDelete.apply(this, [fn]);
  };

  const destroy = TextBuffer.prototype.destroy;
  TextBuffer.prototype.destroy = function() {
    if (inOnDidDeleteCallback) {
      // Don't destroy it.
    } else {
      destroy.apply(this, arguments);
    }
  }

  updatedPrototype = true;
});

[iolsen]

@nathansobo I don't love this, but it works so I went ahead and pushed it anyway for discussion. See also atom/atom#13657.

[nathansobo]

This approach seems fine to me other than the interface for assigning the callback.

[nathansobo]

What about using a constructor parameter named shouldDestroyOnFileDelete instead?

[nathansobo]

👍

[nathansobo]

⚡