Idea Plugin Dev - File and File System (Virtual)

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1 - About

A virtual file com.intellij.openapi.vfs.VirtualFile is the Idea’s representation of a file in a file system (a Virtual File System).

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3 - Management

3.1 - File System (VFS)

3.1.1 - Virtual file system implementation

Most commonly, a virtual file is a file in your local file system. However, the IntelliJ Platform supports multiple pluggable file system implementations, so virtual files can also represent:

  • classes in a JAR file,
  • old revisions of files loaded from a version control repository,
  • and so on.

To provide an alternative file system implementation (for example, an FTP file system):

  • implement the VirtualFileSystem class
  • implement the VirtualFile
  • register your implementation as an application component.

3.1.2 - Build / Refresh

The VFS is built incrementally, by scanning the file system up and down starting from the project root.

New files appearing in the file system are detected by VFS refreshes. A refresh operation can be initiated programmatically using:

  • VirtualFileManager.getInstance().refresh()
  • or VirtualFile.refresh().

VFS refreshes are also triggered whenever file system watchers receive file system change notifications (available on the Windows and Mac operating systems).

As a plugin developer, you may want to invoke a VFS refresh if you need to access a file that has just been created by an external tool through the IntelliJ Platform APIs.

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3.1.3 - Persistence

A particular file on disk is represented by equal VirtualFile instances for the entire lifetime of the IDEA process. There may be several instances corresponding to the same file, and they can be garbage-collected. The file is a UserDataHolder, and the user data is shared between those equal instances. If a file is deleted, its corresponding VirtualFile instance becomes invalid (the isValid() method returns false and operations cause exceptions).

3.1.4 - Extension Point

To hook into operations performed in the local file system (for example, if you are developing a version control system integration that needs custom rename/move handling):

  • implement the LocalFileOperationsHandler interface
  • register it through the LocalFileSystem.registerAuxiliaryFileOperationsHandler method.

3.1.5 - Change Notification

The VirtualFileManager.addVirtualFileListener() method allows you to receive notifications about all changes in the VFS.

3.2 - Directory Tree

3.2.1 - Recursive Operations

Recursive iteration should be performed using VfsUtilCore.iterateChildrenRecursively to prevent endless loops caused by recursive symlinks.

3.3 - File

3.3.1 - Content

The VFS level deals only with binary content. You can get or set the contents of a VirtualFile as a stream of bytes, but concepts like encodings and line separators are handled on higher system levels.

See document which typically corresponds to the text contents of a virtual file.

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3.3.2 - Get

To get a file:

  • From an action: e.getData(PlatformDataKeys.VIRTUAL_FILE). If you are interested in multiple selection, you can also use e.getData(PlatformDataKeys.VIRTUAL_FILE_ARRAY)
  • From a path in the local file system: LocalFileSystem.getInstance().findFileByIoFile()
  • From a PSI file: psiFile.getVirtualFile() (may return null if the PSI file exists only in memory)
  • From a document: FileDocumentManager.getInstance().getFile()

3.3.3 - Creation

3.3.3.1 - Without VFS / External Tool

Usually you don’t create a file through VFS. As a rule, files are created either:

  • through the PSI API
  • or through the regular java/io/File API.

As a plugin developer, you may want to invoke a VFS refresh if you need to access a file that has just been created by an external tool through the IntelliJ Platform APIs.

3.3.3.2 - Through VFS

If you do need to create a file through VFS, you can use the VirtualFile.createChildData() method to create a VirtualFile instance and the VirtualFile.setBinaryContent() method to write some data to the file.

3.3.4 - Scope

A file has an application scope (even if multiple projects are open, each file is represented by the same VirtualFile instance).

4 - Documentation / Reference