The option `--follow-symlinks` can't follow relative symlinks

[kkebo]

Description

The subcommands lint and format have the option --follow-symlinks. However, although it can follow absolute symlinks, it can't follow relative symlinks.

Steps to reproduce

$ mkdir symlink-test
$ cd symlink-test/
$ echo 'let foo:Int=0' > .foo.swift
$ ln -s .foo.swift bar.swift
$ swift format dump-configuration > .swift-format
$ cd ..
$ swift format lint -rs --follow-symlinks symlink-test/
<unknown>: error: Unable to open .foo.swift: file is not readable or does not exist

If the current working directory is the symlink's directory, it works.

$ cd symlink-test
$ swift format lint -rs --follow-symlinks .
.foo.swift:1:9: warning: [Spacing] add 1 space
.foo.swift:1:12: warning: [Spacing] add 1 space
.foo.swift:1:13: warning: [Spacing] add 1 space

It's because the following line is using relativeTo: workingDirectory.

swift-format/Sources/SwiftFormat/Utilities/FileIterator.swift

Line 152 in 8068ff7

URL(fileURLWithPath: relativePath, isDirectory: false, relativeTo: workingDirectory)

Environment

• swift-format (bundled in Swift 6.0.1 toolchain)
• Debian 12 (aarch64)

[ahoppen]

Synced to Apple’s issue tracker as rdar://137341926