Merge pull request #3918 from apple/revert-3909-cherry-redirecting-with

Revert "[VFS] Add a "redirecting-with" field to overlays"

Author: shahmishal

clang/test/VFS/Inputs/redirect-and-fallthrough.yaml

@@ -12,11 +12,3 @@
 // RUN: not %clang_cc1 -ivfsoverlay %S/Inputs/unknown-value.yaml -fsyntax-only %s 2>&1 | FileCheck -check-prefix=CHECK-UNKNOWN-VALUE %s
 // CHECK-UNKNOWN-VALUE: expected boolean value
 // CHECK-UNKNOWN-VALUE: invalid virtual filesystem overlay file
-
-// RUN: not %clang_cc1 -ivfsoverlay %S/Inputs/unknown-redirect.yaml -fsyntax-only %s 2>&1 | FileCheck -check-prefix=CHECK-REDIRECT %s
-// CHECK-REDIRECT: expected valid redirect kind
-// CHECK-REDIRECT: invalid virtual filesystem overlay file
-
-// RUN: not %clang_cc1 -ivfsoverlay %S/Inputs/redirect-and-fallthrough.yaml -fsyntax-only %s 2>&1 | FileCheck -check-prefix=CHECK-EXCLUSIVE-KEYS %s
-// CHECK-EXCLUSIVE-KEYS: 'fallthrough' and 'redirecting-with' are mutually exclusive
-// CHECK-EXCLUSIVE-KEYS: invalid virtual filesystem overlay file

clang/test/VFS/Inputs/unknown-redirect.yaml

@@ -549,10 +549,7 @@ class RedirectingFileSystemParser;
 ///   'case-sensitive': <boolean, default=(true for Posix, false for Windows)>
 ///   'use-external-names': <boolean, default=true>
 ///   'overlay-relative': <boolean, default=false>
-///   'fallthrough': <boolean, default=true, deprecated - use 'redirecting-with'
-///                   instead>
-///   'redirecting-with': <string, one of 'fallthrough', 'fallback', or
-///                        'redirect-only', default='fallthrough'>
+///   'fallthrough': <boolean, default=true>
 ///
 /// Virtual directories that list their contents are represented as
 /// \verbatim
@@ -623,20 +620,6 @@ class RedirectingFileSystem : public vfs::FileSystem {
   enum EntryKind { EK_Directory, EK_DirectoryRemap, EK_File };
   enum NameKind { NK_NotSet, NK_External, NK_Virtual };
 
-  /// The type of redirection to perform.
-  enum class RedirectKind {
-    /// Lookup the redirected path first (ie. the one specified in
-    /// 'external-contents') and if that fails "fallthrough" to a lookup of the
-    /// originally provided path.
-    Fallthrough,
-    /// Lookup the provided path first and if that fails, "fallback" to a
-    /// lookup of the redirected path.
-    Fallback,
-    /// Only lookup the redirected path, do not lookup the originally provided
-    /// path.
-    RedirectOnly
-  };
-
   /// A single file or directory in the VFS.
   class Entry {
     EntryKind Kind;
@@ -771,11 +754,17 @@ class RedirectingFileSystem : public vfs::FileSystem {
   friend class RedirectingFSDirIterImpl;
   friend class RedirectingFileSystemParser;
 
+  bool shouldUseExternalFS() const { return IsFallthrough; }
+
   /// Canonicalize path by removing ".", "..", "./", components. This is
   /// a VFS request, do not bother about symlinks in the path components
   /// but canonicalize in order to perform the correct entry search.
   std::error_code makeCanonical(SmallVectorImpl<char> &Path) const;
 
+  /// Whether to fall back to the external file system when an operation fails
+  /// with the given error code on a path associated with the provided Entry.
+  bool shouldFallBackToExternalFS(std::error_code EC, Entry *E = nullptr) const;
+
   /// Get the File status, or error, from the underlying external file system.
   /// This returns the status with the originally requested name, while looking
   /// up the entry using the canonical path.
@@ -828,9 +817,9 @@ class RedirectingFileSystem : public vfs::FileSystem {
   /// names of files.  This global value is overridable on a per-file basis.
   bool UseExternalNames = true;
 
-  /// Determines the lookups to perform, as well as their order. See
-  /// \c RedirectKind for details.
-  RedirectKind Redirection = RedirectKind::Fallthrough;
+  /// Whether to attempt a file lookup in external file system after it wasn't
+  /// found in VFS.
+  bool IsFallthrough = true;
   /// @}
 
   RedirectingFileSystem(IntrusiveRefCntPtr<FileSystem> ExternalFS);
@@ -885,12 +874,8 @@ class RedirectingFileSystem : public vfs::FileSystem {
 
   StringRef getExternalContentsPrefixDir() const;
 
-  /// Sets the redirection kind to \c Fallthrough if true or \c RedirectOnly
-  /// otherwise. Will removed in the future, use \c setRedirection instead.
   void setFallthrough(bool Fallthrough);
 
-  void setRedirection(RedirectingFileSystem::RedirectKind Kind);
-
   std::vector<llvm::StringRef> getRoots() const;
 
   void dump(raw_ostream &OS) const;