RFR: 8307105: JFileChooser InvalidPathException when selecting some system folders on Windows [v3]

[Alexey Ivanov]

On Wed, 24 May 2023 14:18:02 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

>> `Files.isSymbolicLink`  takes path as argument to check if its a symbolic link. For certain windows specific files as explained the path won't be exact path, rather a hex values. So directly validating with path is causing an exception. So `fsv.isLink()` is used as a first level validation which uses File to check if its valid. I didn't find any other alternatives to validate the file path, so used `fsv.isLink` as first level validation along with Symbolic Link check.
>
> I understand that, virtual folders don't have a filesystem path, this is why `fsv.isFileSystem(f)` should handle this situation. The implementation of `FileSystemView.isFileSystem` explicitly excludes such files which are both `isLink` and `isDirectory`:
> https://github.com/openjdk/jdk/blob/d7245f70e7bac1236bbcdcd9b25346ca22ab8bb2/src/java.desktop/share/classes/javax/swing/filechooser/FileSystemView.java#L382-L388
> 
> Let's look deeper:
> https://github.com/openjdk/jdk/blob/d7245f70e7bac1236bbcdcd9b25346ca22ab8bb2/src/java.desktop/windows/classes/sun/awt/shell/Win32ShellFolder2.java#L591-L597
> 
> https://github.com/openjdk/jdk/blob/d7245f70e7bac1236bbcdcd9b25346ca22ab8bb2/src/java.desktop/windows/classes/sun/awt/shell/Win32ShellFolder2.java#L860-L866
> 
> The `hasAttribute` method uses `getAttributes0` which calls [`IShellFolder::GetAttributesOf`](https://learn.microsoft.com/en-us/windows/win32/api/shobjidl_core/nf-shobjidl_core-ishellfolder-getattributesof) which returns [`SFGAO`](https://learn.microsoft.com/en-us/windows/win32/shell/sfgao). The attribute `SFGAO_LINK` which corresponds to `ATTRIB_LINK` in Java is described as _“The specified items are shortcuts.”_ That is it is a shell folder shortcut with `.lnk` file extension, which used to be the case.
> 
> However, now this attribute is set for both [_symbolic links_](https://learn.microsoft.com/en-us/windows/win32/fileio/creating-symbolic-links) and [_junctions_](https://learn.microsoft.com/en-us/windows/win32/fileio/hard-links-and-junctions#junctions).
> 
> Here's what different methods return:
> 
> file: C:\test\symbolic-links\jdk - junction
> 	isFileSystem   false
> 	isLink         true
> 	isDirectory    true
> 	isSymbolicLink false
> Absolute Path : null
> 
> file: C:\test\symbolic-links\jdk - symbolic
> 	isFileSystem   false
> 	isLink         true
> 	isDirectory    true
> 	isSymbolicLink true
> Absolute Path : C:\test\symbolic-links\jdk - symbolic
> 
> file: C:\test\symbolic-links\jdk - shortcut.lnk
> 	isFileSystem   false
> 	isLink         true
> 	isDirectory    true
> 	isSymbolicLink false
> Absolute Path : null
> 
> 
> In the three cases above, `isFileSystem` returns `false` even though all the three objects point to a filesystem directory, the first two are fully transparent for apps whereas the `.lnk` shortcut needs special handling.
> 
> If `JFileChooser` is in directory-only mode, selecting a junction or `.lnk` file results in selected file being to `null`; symbolic links are supported with your fix.
> 
> So, **I propose mod...

Handling `.lnk` files on Windows doesn't seem right: `JFileChooser` allows selecting such a file.

* If it's a shortcut to a directory, clicking Open in the file chooser or double-clicking it in the list navigates to the target.
* If it's a shortcut to a regular file, `JFileChooser` returns this file which isn't helpful, it's not what the user usually wants, the target of the shortcut should be returned. This is what happens if the user selects a shortcut file (`.lnk`) in the native file chooser.

In addition to that, the shortcuts are filtered based on the file types. For example, if select the *Open* command in Notepad, the file chooser shows only shortcuts to `.txt` files (as well as `.txt` files), it hides shortcuts to other file types.

But `JFileChooser` doesn't show `.lnk` files at all if an extension filter is set.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13998#discussion_r1204423861