[REPL] Fix shell completion error on unreadable symlink (JuliaLang#51851

)

In macOS there is a file, `/usr/sbin/weakpass_edit` that is a symlink to
a directory that is only readable by `root`. Our REPL shell completion
attempts to call `isfile()` when entering the shell mode and pressing
`w`, throwing an ugly error into the REPL.

This PR fixes the root cause (skipping files that fail the `isfile()`
condition) and adds a test that synthesizes an analogous condition.

stdlib/REPL/src/REPLCompletions.jl

@@ -329,8 +329,19 @@ function complete_path(path::AbstractString, pos::Int;
  for file in filesinpath
  # In a perfect world, we would filter on whether the file is executable
  # here, or even on whether the current user can execute the file in question.
- if startswith(file, prefix) && isfile(joinpath(pathdir, file))
- push!(matches, file)
+ try
+ if startswith(file, prefix) && isfile(joinpath(pathdir, file))
+ push!(matches, file)
+ end
+ catch e
+ # `isfile()` can throw in rare cases such as when probing a
+ # symlink that points to a file within a directory we do not
+ # have read access to.
+ if isa(e, Base.IOError)
+ continue
+ else
+ rethrow()
+ end
  end
  end
  end

stdlib/REPL/test/replcompletions.jl

@@ -1119,28 +1119,35 @@ let s, c, r
  end
 
  # Tests detecting of files in the env path (in shell mode)
- let path, file
- path = tempdir()
- unreadable = joinpath(tempdir(), "replcompletion-unreadable")
+ mktempdir() do path
+ unreadable = joinpath(path, "replcompletion-unreadable")
+ file = joinpath(path, "tmp-executable")
+ touch(file)
+ chmod(file, 0o755)
+ mkdir(unreadable)
+ hidden_file = joinpath(unreadable, "hidden")
+ touch(hidden_file)
 
- try
- file = joinpath(path, "tmp-executable")
- touch(file)
- chmod(file, 0o755)
- mkdir(unreadable)
- chmod(unreadable, 0o000)
+ # Create symlink to a file that is in an unreadable directory
+ chmod(hidden_file, 0o755)
+ chmod(unreadable, 0o000)
+ symlink(hidden_file, joinpath(path, "replcompletions-link"))
 
+ try
  # PATH can also contain folders which we aren't actually allowed to read.
  withenv("PATH" => string(path, ":", unreadable)) do
  s = "tmp-execu"
  c,r = test_scomplete(s)
  @test "tmp-executable" in c
  @test r == 1:9
  @test s[r] == "tmp-execu"
+
+ c,r = test_scomplete("replcompletions-link")
+ @test isempty(c)
  end
  finally
- rm(file)
- rm(unreadable)
+ # If we don't fix the permissions here, our cleanup fails.
+ chmod(unreadable, 0o700)
  end
  end