[FileSystem] Add expand_tilde function

[JDevlieghere]

Summary

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.

[JDevlieghere]

Update unit test.

[zturner]

llvm/unittests/Support/Path.cpp

534–536

I don't think we need these lines?

550

Or this line?

[JDevlieghere]

Remove useless copy-pasted lines from unit test.

[sammccall]

Thanks! Only real substantial suggestion is not to require handling an error where none is possible.

llvm/include/llvm/Support/FileSystem.h

352

it'd be worth explicitly stating whether ~user is handled, whether $ENVVAR is handled, and what this does on windows.

355

this can't fail, remove the error_code return?

then it can return its result, which makes it a bit easier to use.

llvm/lib/Support/Unix/Path.inc

554

the much richer alternative on unix is to wrap wordexp(), which more precisely emulates a shell.
I can imagine there are reasons not to do that (e.g. quoting surprises, performance), but it may be worth a comment.

llvm/unittests/Support/Path.cpp

538

is there any reason for this to fail? Maybe assert it instead so the test doesn't silently become a no-op?

540

also test ~/foo?

(would be nice to have a test for ~username on unix, but not sure if it's easy to make that work)

[JDevlieghere]

Thanks for the review Sam!

llvm/lib/Support/Unix/Path.inc

554

I don't know the history/reason for the current implementation so I don't feel confident adding a comment.

llvm/unittests/Support/Path.cpp

538

Added a comment.

llvm/include/llvm/Support/FileSystem.h

 ///
 /// @param path The path to resolve.
 /// @param output The location to store the resolved path.
 /// @param expand_tilde If true, resolves ~ expressions to the user's home
 ///                     directory.
 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.
 /// @returns errc::success if the current path has been stored in result,
 ///          otherwise a platform-specific error_code.
 std::error_code current_path(SmallVectorImpl<char> &result);
 
 /// Set the current path.

llvm/lib/Support/Unix/Path.inc

static void expandTildeExpr(SmallVectorImpl<char> &Path) {
   }
 
   Storage = Remainder;
   Path.clear();
   Path.append(Entry->pw_dir, Entry->pw_dir + strlen(Entry->pw_dir));
   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;
   else if (S_ISREG(Mode))
     return file_type::regular_file;
   else if (S_ISBLK(Mode))
     return file_type::block_file;
   else if (S_ISCHR(Mode))

llvm/lib/Support/Windows/Path.inc

if (!path::home_directory(HomeDir)) {
     return;
   }
 
   // Overwrite the first character and insert the rest.
   Path[0] = HomeDir[0];
   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();
   if (path.isTriviallyEmpty())
     return std::error_code();
 
   if (expand_tilde) {
     SmallString<128> Storage;

llvm/unittests/Support/Path.cpp

TEST_F(FileSystemTest, RealPath) {
   path::native(Twine(RealBase) + "/test1/test2", Expected);
 
   ASSERT_NO_ERROR(fs::real_path(
       Twine(TestDirectory) + "/././test1/../test1/test2/./test3/..", Actual));
 
   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));
     ASSERT_NO_ERROR(fs::real_path("~", Actual, true));
     EXPECT_EQ(Expected, Actual);
     ASSERT_NO_ERROR(fs::real_path("~/", Actual, true));
     EXPECT_EQ(Expected, Actual);
   }
 
   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;
 
   ASSERT_NO_ERROR(
     fs::create_directories(Twine(TestDirectory) + "/noreadperm"));
   ASSERT_TRUE(fs::exists(Twine(TestDirectory) + "/noreadperm"));