[VFS] Remove 'ignore-non-existent-contents' attribute for YAML-based VFS.

'ignore-non-existent-contents' stopped working after r342232 in a way
that the actual attribute value isn't used and it works as if it is
always `true`.

Common use case for VFS iteration is iterating through files in umbrella
directories for modules. Ability to detect if some VFS entries point to
non-existing files is nice but non-critical. Instead of adding back
support for `'ignore-non-existent-contents': false` I am removing the
attribute, because such scenario isn't used widely enough and stricter
checks don't provide enough value to justify the maintenance.

rdar://problem/45176119

Reviewers: bruno

Reviewed By: bruno

Subscribers: hiraditya, dexonsmith, sammccall, cfe-commits

Differential Revision: https://reviews.llvm.org/D53228

llvm-svn: 345212

clang/lib/Frontend/ModuleDependencyCollector.cpp

@@ -156,10 +156,6 @@ void ModuleDependencyCollector::writeFileMap() {
   // allows crash reproducer scripts to work across machines.
   VFSWriter.setOverlayDir(VFSDir);
 
-  // Do not ignore non existent contents otherwise we might skip something
-  // that should have been collected here.
-  VFSWriter.setIgnoreNonExistentContents(false);
-
   // Explicitly set case sensitivity for the YAML writer. For that, find out
   // the sensitivity at the path where the headers all collected to.
   VFSWriter.setCaseSensitivity(isCaseSensitivePath(VFSDir));

clang/test/Modules/crash-vfs-headermaps.m

@@ -32,7 +32,6 @@
 // CHECKYAML: 'case-sensitive':
 // CHECKYAML-NEXT: 'use-external-names': 'false',
 // CHECKYAML-NEXT: 'overlay-relative': 'true',
-// CHECKYAML-NEXT: 'ignore-non-existent-contents': 'false'
 // CHECKYAML: 'type': 'directory'
 // CHECKYAML: 'name': "/[[PATH:.*]]/Foo.framework/Headers",
 // CHECKYAML-NEXT: 'contents': [

clang/test/Modules/crash-vfs-include-pch.m

@@ -33,7 +33,6 @@ void g() { double x = DBL_MAX; }
 // CHECKYAML: 'case-sensitive':
 // CHECKYAML-NEXT: 'use-external-names': 'false',
 // CHECKYAML-NEXT: 'overlay-relative': 'true',
-// CHECKYAML-NEXT: 'ignore-non-existent-contents': 'false'
 // CHECKYAML: 'type': 'directory'
 // CHECKYAML: 'name': "/[[PATH:.*]]/out",
 // CHECKYAML-NEXT: 'contents': [

clang/test/Modules/crash-vfs-ivfsoverlay.m

@@ -36,7 +36,6 @@
 // CHECKYAML: 'case-sensitive':
 // CHECKYAML-NEXT: 'use-external-names': 'false',
 // CHECKYAML-NEXT: 'overlay-relative': 'true',
-// CHECKYAML-NEXT: 'ignore-non-existent-contents': 'false'
 // CHECKYAML: 'type': 'directory'
 // CHECKYAML: 'name': "/[[PATH:.*]]/example"
 // CHECKYAML: 'contents': [

clang/test/Modules/crash-vfs-relative-incdir.m

@@ -36,7 +36,6 @@
 // CHECKYAML: 'case-sensitive':
 // CHECKYAML-NEXT: 'use-external-names': 'false',
 // CHECKYAML-NEXT: 'overlay-relative': 'true',
-// CHECKYAML-NEXT: 'ignore-non-existent-contents': 'false'
 // CHECKYAML: 'type': 'directory'
 // CHECKYAML: 'name': "/[[PATH:.*]]/Inputs/crash-recovery/usr/include",
 // CHECKYAML-NEXT: 'contents': [

clang/test/Modules/crash-vfs-run-reproducer.m

@@ -36,7 +36,6 @@
 // CHECKYAML: 'case-sensitive':
 // CHECKYAML-NEXT: 'use-external-names': 'false',
 // CHECKYAML-NEXT: 'overlay-relative': 'true',
-// CHECKYAML-NEXT: 'ignore-non-existent-contents': 'false'
 // CHECKYAML: 'type': 'directory'
 // CHECKYAML: 'name': "/[[PATH:.*]]/Inputs/crash-recovery/usr/include",
 // CHECKYAML-NEXT: 'contents': [

clang/test/VFS/Inputs/MissingVFS/vfsoverlay.yaml

@@ -1,6 +1,5 @@
 {
   'version': 0,
-  'ignore-non-existent-contents': false,
   'roots': [
     { 'name': 'INPUT_DIR', 'type': 'directory',
       'contents': [

clang/test/VFS/Inputs/Nonmodular/nonmodular-headers.yaml

@@ -1,7 +1,6 @@
 {
   'version': 0,
   'case-sensitive': 'false',
-  'ignore-non-existent-contents': 'true',
   'roots': [
     {
       'type': 'directory',

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

@@ -1,7 +1,6 @@
 {
   'version': 0,
   'case-sensitive': 'false',
-  'ignore-non-existent-contents': 'true',
   'roots': [
     {
       'type': 'directory',

clang/test/VFS/Inputs/vfsoverlay2.yaml

@@ -1,6 +1,5 @@
 {
   'version': 0,
-  'ignore-non-existent-contents': false,
   'roots': [
     { 'name': 'OUT_DIR', 'type': 'directory',
       'contents': [