From: "andrykonchin (Andrew Konchin) via ruby-core" <ruby-core@...>
Date: 2026-07-13T19:00:50+00:00
Subject: [ruby-core:126077] [Ruby Bug#22194] File.realpath and File.realdirpath handle differently path encoding incompatible to a filesystem's one

Issue #22194 has been reported by andrykonchin (Andrew Konchin).

----------------------------------------
Bug #22194: File.realpath and File.realdirpath handle differently path encoding incompatible to a filesystem's one
https://bugs.ruby-lang.org/issues/22194

* Author: andrykonchin (Andrew Konchin)
* Status: Open
* Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN
----------------------------------------
Both `realpath` and `realdirpath` methods accept a `path` parameter and try to return result in the `path`'s encoding.

`realpath`:

```ruby
File.realpath(".rubocop.yml").encoding # => #<Encoding:UTF-8>
File.realpath(".rubocop.yml".encode("US-ASCII")).encoding # => #<Encoding:US-ASCII>
```

`realdirpath`:

```ruby
File.realdirpath("src").encoding # => #<Encoding:UTF-8>
File.realdirpath("src".encode("US-ASCII")).encoding # => #<Encoding:US-ASCII>
```

But it's possible that `path`'s encoding isn't compatible to the filesystem's one (that's is common to be UTF-8 on Linux and macOS), that's converting from the filesystem's encoding to `path`'s encoding fails.

In this case `realpath` and `realdirpath` behaves differently - `realpath` just "forces" encoding to `path`'s one (and as fallback to filesystem's and then to binary if a string becomes broken) and `realdirpath` just returns a string in the filesystem's encoding.

`realpath`:

```ruby
File.realpath(".".encode(Encoding::ISO_8859_1), "test_dir_����").encoding # => #<Encoding:ISO-8859-1>
```

`realdirpath`:

```ruby
File.realdirpath(".".encode(Encoding::ISO_8859_1), "test_dir_����").encoding # => #<Encoding:UTF-8>
```

It makes sense for the methods to handle this edge case consistently.




-- 
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