Reapply [VFS] Skip non existent files from the VFS tree

Reapply r278457 with test fixed to not abouse fs case sensitivity.

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: 278543

clang/lib/Basic/VirtualFileSystem.cpp

@@ -1778,29 +1778,47 @@ VFSFromYamlDirIterImpl::VFSFromYamlDirIterImpl(
     RedirectingDirectoryEntry::iterator Begin,
     RedirectingDirectoryEntry::iterator End, std::error_code &EC)
     : Dir(_Path.str()), FS(FS), Current(Begin), End(End) {
-  if (Current != End) {
+  while (Current != End) {
     SmallString<128> PathStr(Dir);
     llvm::sys::path::append(PathStr, (*Current)->getName());
     llvm::ErrorOr<vfs::Status> S = FS.status(PathStr);
-    if (S)
+    if (S) {
       CurrentEntry = *S;
-    else
+      return;
+    }
+    // Skip entries which do not map to a reliable external content.
+    if (FS.ignoreNonExistentContents() &&
+        S.getError() == llvm::errc::no_such_file_or_directory) {
+      ++Current;
+      continue;
+    } else {
       EC = S.getError();
+      break;
+    }
   }
 }
 
 std::error_code VFSFromYamlDirIterImpl::increment() {
   assert(Current != End && "cannot iterate past end");
-  if (++Current != End) {
+  while (++Current != End) {
     SmallString<128> PathStr(Dir);
     llvm::sys::path::append(PathStr, (*Current)->getName());
     llvm::ErrorOr<vfs::Status> S = FS.status(PathStr);
-    if (!S)
-      return S.getError();
+    if (!S) {
+      // Skip entries which do not map to a reliable external content.
+      if (FS.ignoreNonExistentContents() &&
+          S.getError() == llvm::errc::no_such_file_or_directory) {
+        continue;
+      } else {
+        return S.getError();
+      }
+    }
     CurrentEntry = *S;
-  } else {
-    CurrentEntry = Status();
+    break;
   }
+
+  if (Current == End)
+    CurrentEntry = Status();
   return std::error_code();
 }
 

clang/test/VFS/Inputs/Bar.framework/Headers/A.h

@@ -0,0 +1 @@
+// A.h

clang/test/VFS/Inputs/Bar.framework/Headers/B.h

@@ -0,0 +1 @@
+// B.h

clang/test/VFS/Inputs/Bar.framework/Headers/C.h

@@ -0,0 +1 @@
+// C.h

clang/test/VFS/Inputs/Bar.framework/Modules/module.modulemap

@@ -0,0 +1,6 @@
+framework module Bar [extern_c] {
+  umbrella "Headers"
+  export *
+  module * { export * }
+}
+

clang/test/VFS/Inputs/bar-headers.yaml

@@ -0,0 +1,39 @@
+{
+  'version': 0,
+  'case-sensitive': 'false',
+  'ignore-non-existent-contents': 'true',
+  'roots': [
+    {
+      'type': 'directory',
+      'name': "VDIR/Bar.framework/Headers",
+      'contents': [
+        {
+          'type': 'file',
+          'name': "A.h",
+          'external-contents': "OUT_DIR/Bar.framework/Headers/A.h"
+        },
+        {
+          'type': 'file',
+          'name': "B.h",
+          'external-contents': "OUT_DIR/Bar.framework/Headers/B.h"
+        },
+        {
+          'type': 'file',
+          'name': "C.h",
+          'external-contents': "OUT_DIR/Bar.framework/Headers/C.h"
+        }
+      ]
+    },
+    {
+      'type': 'directory',
+      'name': "VDIR/Bar.framework/Modules",
+      'contents': [
+        {
+          'type': 'file',
+          'name': "module.modulemap",
+          'external-contents': "OUT_DIR/Bar.framework/Modules/module.modulemap"
+        }
+      ]
+    },
+  ]
+}

clang/test/VFS/umbrella-framework-import-skipnonexist.m

@@ -0,0 +1,14 @@
+// REQUIRES: crash-recovery, shell
+
+// FIXME: This XFAIL is cargo-culted from crash-report.c. Do we need it?
+// XFAIL: mingw32
+
+// RUN: rm -rf %t
+// RUN: mkdir -p %t/vdir %t/outdir %t/cache
+// RUN: cp -a %S/Inputs/Bar.framework %t/outdir/
+//
+// RUN: sed -e "s:VDIR:%t/vdir:g" -e "s:OUT_DIR:%t/outdir:g" %S/Inputs/bar-headers.yaml > %t/vdir/bar-headers.yaml
+// RUN: rm -f %t/outdir/Bar.framework/Headers/B.h
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t/cache -ivfsoverlay %t/vdir/bar-headers.yaml -F %t/vdir -fsyntax-only %s
+
+@import Bar;