[PATCH] D94844: [VFS] Add support to RedirectingFileSystem for mapping a virtual directory to one in the external FS.

[Nathan Hawes via Phabricator via llvm-commits]

nathawes created this revision.
nathawes added a reviewer: JDevlieghere.
Herald added subscribers: dexonsmith, hiraditya.
nathawes requested review of this revision.
Herald added projects: clang, LLVM.
Herald added subscribers: llvm-commits, cfe-commits.

Previously file entries in the -ivfsoverlay yaml could map to a file in the external file system (specified via the 'external-contents' property, taking a path), but directories had to list their contents in the form of other file or directory entries (via the 'contents' property, taking an array). Allowing directory entries to map to a directory in the external file system (via the same 'external-contents' property as file entries) makes it possible to present an external directory's contents in a different location and, in combination with the 'fallthrough' option, overlay one directory's contents on top of another.

As an example, with the yaml below:

  { 'roots': [
    {
      'type': 'directory',
      'name': '//root/',
      'contents': [
        {
          'type': 'directory',
          'name': 'mappeddir',
          'external-contents': '//root/foo/bar'
        }
      ]
    }
  ]}

The path '//root/mappeddir/somefile' would map to '//root/foo/bar/somefile' in the external file system. If that file wasn't found in the external file system and the 'fallthrough' configuration option is true, it would fall back to checking for '//root/mappeddir/somefile' in the external file system. This effectively overlays the contents of //root/foo/bar/ on top of //root/mappeddir.

      

This patch also refactors OverlayFileSystem's directory iterator implementation (OverlayFSDirIterImpl) and VFSFromYamlDirIterImpl into a single implementation, addressing a FIXME about their conceptual similarity.

Resolves rdar://problem/72485443


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D94844

Files:
  clang/test/VFS/Inputs/vfsoverlay-directory-relative.yaml
  clang/test/VFS/Inputs/vfsoverlay-directory.yaml
  clang/test/VFS/directory.c
  llvm/include/llvm/Support/VirtualFileSystem.h
  llvm/lib/Support/VirtualFileSystem.cpp
  llvm/unittests/Support/VirtualFileSystemTest.cpp

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