[FileSystem] Add expand_tilde function

In D54435 there was some discussion about the expand_tilde flag for
real_path that I wanted to expose through the VFS. The consensus is that
these two things should be separate functions. Since we already have the
code for this I went ahead and added a function expand_tilde that does
just that.

Differential revision: https://reviews.llvm.org/D54448

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@346776 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Support/FileSystem.h

@@ -349,6 +349,12 @@ std::error_code create_hard_link(const Twine &to, const Twine &from);
 std::error_code real_path(const Twine &path, SmallVectorImpl<char> &output,
                           bool expand_tilde = false);
 
+/// Expands ~ expressions to the user's home directory. On Unix ~user
+/// directories are resolved as well.
+///
+/// @param path The path to resolve.
+void expand_tilde(const Twine &path, SmallVectorImpl<char> &output);
+
 /// Get the current path.
 ///
 /// @param result Holds the current path on return.

lib/Support/Unix/Path.inc

@@ -550,6 +550,18 @@ static void expandTildeExpr(SmallVectorImpl<char> &Path) {
   llvm::sys::path::append(Path, Storage);
 }
 
+
+void expand_tilde(const Twine &path, SmallVectorImpl<char> &dest) {
+  dest.clear();
+  if (path.isTriviallyEmpty())
+    return;
+
+  path.toVector(dest);
+  expandTildeExpr(dest);
+
+  return;
+}
+
 static file_type typeForMode(mode_t Mode) {
   if (S_ISDIR(Mode))
     return file_type::directory_file;

lib/Support/Windows/Path.inc

@@ -1253,6 +1253,17 @@ static void expandTildeExpr(SmallVectorImpl<char> &Path) {
   Path.insert(Path.begin() + 1, HomeDir.begin() + 1, HomeDir.end());
 }
 
+void expand_tilde(const Twine &path, SmallVectorImpl<char> &dest) {
+  dest.clear();
+  if (path.isTriviallyEmpty())
+    return;
+
+  path.toVector(dest);
+  expandTildeExpr(dest);
+
+  return;
+}
+
 std::error_code real_path(const Twine &path, SmallVectorImpl<char> &dest,
                           bool expand_tilde) {
   dest.clear();

unittests/Support/Path.cpp

@@ -516,6 +516,8 @@ TEST_F(FileSystemTest, RealPath) {
   EXPECT_EQ(Expected, Actual);
 
   SmallString<64> HomeDir;
+
+  // This can fail if $HOME is not set and getpwuid fails.
   bool Result = llvm::sys::path::home_directory(HomeDir);
   if (Result) {
     ASSERT_NO_ERROR(fs::real_path(HomeDir, Expected));
@@ -528,6 +530,25 @@ TEST_F(FileSystemTest, RealPath) {
   ASSERT_NO_ERROR(fs::remove_directories(Twine(TestDirectory) + "/test1"));
 }
 
+TEST_F(FileSystemTest, ExpandTilde) {
+  SmallString<64> Expected;
+  SmallString<64> Actual;
+  SmallString<64> HomeDir;
+
+  // This can fail if $HOME is not set and getpwuid fails.
+  bool Result = llvm::sys::path::home_directory(HomeDir);
+  if (Result) {
+    fs::expand_tilde(HomeDir, Expected);
+
+    fs::expand_tilde("~", Actual);
+    EXPECT_EQ(Expected, Actual);
+
+    path::append(Expected, "foo");
+    fs::expand_tilde("~/foo", Actual);
+    EXPECT_EQ(Expected, Actual);
+  }
+}
+
 #ifdef LLVM_ON_UNIX
 TEST_F(FileSystemTest, RealPathNoReadPerm) {
   SmallString<64> Expanded;