During the last weeks I have got  a few questions about rename refactoring and some users also complain to me that the refactoring in NetBeans 6.x was much faster. So I would like to explain the situation.

For some people, who don't know, Instant Rename action and Rename Refactoring  can look like one action. But it's not true, even if  both actions use the same shortcut (CTRL + R). NetBeans 6.x contained only Instant Rename action (speaking about PHP support), which we can mark as very simple rename refactoring through one file.

From NetBeans 7.0 the Instant Rename action works only in "non public" context. It means that this action is used for fast renaming variables that has local context like inside a method, or for renaming private methods and fields that can not be used outside of the scope, where they are declared.

From user point of view these two action can be simply recognized. When is after CTRL+R called Instant Rename action, then the identifier is surrounded with rectangle and you can rename it directly in the file. It's fast and simple, also the usages of this identifier are renamed in the same time as you write.

The picture below shows Instant Rename action for $message identifier, that is visible only in the print_test method and due this after CTRL+R is called Instant Rename.

In NetBeans 7.0, there was added Rename Refactoring that is called for public identifiers. It means for identifiers that could be used in other files. If you press CTRL+R shortcut when the caret is inside $hello identifier from the picture above, NetBeans recognizes that $hello is declared / used in a global context and calls the Rename Refactoring that brings a dialog to change the name of the identifier. From this dialog you have to preview suggested changes, through pressing Preview button and then execute the refactoring through Do Refactoring button.

Yes, it's more complicated from user point of view than Instant Rename, but in Rename Refactoring NetBeans can change more files at once. It should be  the developer responsibility to decide whether the suggested changes are right and the refactoring can be executed or in some files original name should be kept.

Someone can argue that he doesn't use $hello variable in any other file so Instant Rename could be used in such case. Yes it's true, but in such case NetBeans has to know all usages of all identifiers and keep this informations up to date during editing a file. I'm sure that this is not possible due to the performance problems, mainly for big projects. So the usages are computed after pressing the Preview button.

And why is the Refactor button always disabled in the Rename dialog and user has to always go through the preview phase? NetBeans has API and SPI for implementing refactoring actions and this dialog is a part of this infrastructure. If you rename an identifier for example in Java, the Refactor buttons is enabled, but Java is strongly type language and you can be almost in 99% sure that the IDE will suggest the right results. In PHP as a dynamic language, we can not be sure, what NetBeans finds is only a "guess". This is why NetBeans pushes developers to preview the changes for PHP rename.

I hope that I have explain it clearly. I'm open to any discussion. What I have described above is situation in NetBeans 7.0, 7.0.1 and probably it will be also in NetBeans 7.1, because there is no plan to change it. Please write your opinion here.