[VFS] Implement `RedirectingFileSystem::getRealPath`.

It fixes the case when Objective-C framework is added as a subframework
through a symlink. When parent framework infers a module map and fails
to detect a symlink, it would add a subframework as a submodule. And
when we parse module map for the subframework, we would encounter an
error like

> error: umbrella for module 'WithSubframework.Foo' already covers this directory

By implementing `getRealPath` "an egregious but useful hack" in
`ModuleMap::inferFrameworkModule` works as expected.

LLVM commit is r347009.

rdar://problem/45821279

Reviewers: bruno, benlangmuir, erik.pilkington

Reviewed By: bruno

Subscribers: hiraditya, dexonsmith, JDevlieghere, cfe-commits, llvm-commits

Differential Revision: https://reviews.llvm.org/D54245

llvm-svn: 347012

1 files changed, 23 insertions, 0 deletions

diff --git a/clang/test/VFS/subframework-symlink.m b/clang/test/VFS/subframework-symlink.m
new file mode 100644
index 00000000000..1c6fd064093
--- /dev/null
+++ b/clang/test/VFS/subframework-symlink.m
@@ -0,0 +1,23 @@
+// REQUIRES: shell
+
+// Test that when a subframework is a symlink to another framework, we don't
+// add it as a submodule to the enclosing framework. We also need to make clang
+// to infer module for the enclosing framework. For this we don't have
+// a module map for the framework itself but have it in a parent directory.
+//
+// RUN: rm -rf %t
+// RUN: mkdir %t
+// RUN: echo 'framework module * {}' > %t/module.modulemap
+// RUN: mkdir -p %t/WithSubframework.framework/Headers
+// RUN: echo '#include <Foo/Foo.h>' > %t/WithSubframework.framework/Headers/WithSubframework.h
+// RUN: cp -R %S/Inputs/Foo.framework %t
+// RUN: mkdir -p %t/WithSubframework.framework/Frameworks
+// RUN: ln -s %t/Foo.framework %t/WithSubframework.framework/Frameworks
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t/cache1 -F %t -fsyntax-only %s
+
+// Adding VFS overlay shouldn't change this behavior.
+//
+// RUN: sed -e "s:INPUT_DIR:/InvalidPath:g" -e "s:OUT_DIR:/InvalidPath:g" %S/Inputs/vfsoverlay.yaml > %t/overlay.yaml
+// RUN: %clang_cc1 -fmodules -fimplicit-module-maps -fmodules-cache-path=%t/cache2 -F %t -fsyntax-only %s -ivfsoverlay %t/overlay.yaml
+
+#import <WithSubframework/WithSubframework.h>