[VFS] Skip non existent files from the VFS tree

When the VFS uses a YAML file, the real file path for a
virtual file is described in the "external-contents" field. Example:

  ...
  {
     'type': 'file',
     'name': 'a.h',
     'external-contents': '/a/b/c/a.h'
  }

Currently, when parsing umbrella directories, we use
vfs::recursive_directory_iterator to gather the header files to generate the
equivalent modules for. If the external contents for a header does not exist,
we currently are unable to build a module, since the VFS
vfs::recursive_directory_iterator will fail when it finds an entry without a
reliable real path.

Since the YAML file could be prepared ahead of time and shared among
different compiler invocations, an entry might not yet have a reliable
path in 'external-contents', breaking the iteration.

Give the VFS the capability to skip such entries whenever
'ignore-non-existent-contents' property is set in the YAML file.

rdar://problem/27531549

llvm-svn: 278457

1 files changed, 6 insertions, 0 deletions

diff --git a/clang/test/VFS/Inputs/Bar.framework/Modules/module.modulemap b/clang/test/VFS/Inputs/Bar.framework/Modules/module.modulemap
new file mode 100644
index 00000000000..d5c759aceb7
--- /dev/null
+++ b/clang/test/VFS/Inputs/Bar.framework/Modules/module.modulemap
@@ -0,0 +1,6 @@
+framework module Bar [extern_c] {
+  umbrella "Headers"
+  export *
+  module * { export * }
+}
+