fs::file_info hangs for symlinks of symlinks

[DE0CH]

It seems like fs::is_file('/opt/homebrew/bin/python3') hangs on Mac with homebrew python installed. This doesn't seem to be a Mac specific bug because I was able to reproduce it by recreating the folder structure and symlinks on a linux computer I have.

Steps to reproduce

Create symlinks and folder structure with the script below

mkdir -p opt/homebrew/Cellar/[email protected]/3.11.6_1/Frameworks/Python.framework/Versions/3.11/bin
cd opt/homebrew/Cellar/[email protected]/3.11.6_1/Frameworks/Python.framework/Versions/3.11/bin
echo "#!/bin/sh
echo 'hi'
" > python3.11
chmod +x python3.11
ln -s python3.11 python3
cd ../../../../../../../../../../
mkdir -p opt/homebrew/Cellar/[email protected]/3.11.6_1/bin
cd opt/homebrew/Cellar/[email protected]/3.11.6_1/bin
ln -s ../Frameworks/Python.framework/Versions/3.11/bin/python3 python3
cd ../../../../../../
mkdir -p opt/homebrew/bin
cd opt/homebrew/bin
ln -s ../Cellar/[email protected]/3.11.6_1/bin/python3 python3
cd ../../../

And then run fs::is_file('opt/homebrew/bin/python3') to see it hangs.

Version Information

$ R --version
R version 4.1.2 (2021-11-01) -- "Bird Hippie"
Copyright (C) 2021 The R Foundation for Statistical Computing
Platform: x86_64-pc-linux-gnu (64-bit)

I installed the version of fs from GitHub, which is at 8a84fc9 at the time of writing.

[MLopez-Ibanez]

A pure R reproducer:

library(fs)
file_touch("file")
link_create("file", "link1")
link_create("link1", "link2")
is_file("link2")

It seems the loop that follows symlinks is broken:

fs/R/file.R

Lines 64 to 69 in 8a84fc9

	while(follow && any(is_symlink)) {
	lpath <- link_path(path[is_symlink])
	lpath <- ifelse(is_absolute_path(lpath), lpath, path(path_dir(path[is_symlink]), lpath))
	res[is_symlink, ] <- file_info(lpath, fail = fail, follow = FALSE)
	is_symlink <- !is.na(res$type) & res$type == "symlink"
	}

path is never updated within the loop, so lpath has the same value in the second iteration.

[MLopez-Ibanez]

This is not only on Mac, I am using Ubuntu 20.04.

[MLopez-Ibanez]

And the bug is actually in file_info(), so any function using that is affected.