Precompilation fails when STDOUT is an IOStream

[garrison]

Consider the following very simple test.jl:

@show typeof(STDOUT)
using Compat

If run such that STDOUT is a tty, the precompilation succeeds. However, if STDOUT is not a tty, it fails:

$ rm -f ~/.julia/lib/v0.4/Compat.ji
$ julia test.jl > /tmp/outfile
ERROR: LoadError: MethodError: `open` has no method matching open(::Cmd, ::ASCIIString, ::IOStream)
Closest candidates are:
  open(!Matched::Function, ::Any...)
  open(::Base.AbstractCmd, ::AbstractString)
  open(::Base.AbstractCmd, ::AbstractString, !Matched::Base.AsyncStream)
  ...
 in create_expr_cache at loading.jl:303
 in compilecache at loading.jl:349
 in require at ./loading.jl:217
 in include at ./boot.jl:260
 in include_from_node1 at ./loading.jl:271
 in process_options at ./client.jl:308
 in _start at ./client.jl:411
while loading /tmp/test.jl, in expression starting on line 5

Possibly (?) related: #12941

[vtjnash]

fixed by #12839

[garrison]

One annoying thing about this bug is that you can establish a workflow that seems to work reliably, but fails as soon as you run Pkg.update() and things need to be re-precompiled. This could be an unwelcome surprise to anyone using julia in production (if their workflow involves directing stdout to a file) if this is not fixed before 0.4 final.

(In other words, if #12839 is not going to make it into release-0.4, I think some fix should.)

[garrison]

I'm going to add this to the 0.4.0 milestone because it is a regression in behavior from 0.3. Feel free to move to a later milestone if you don't think this bug should hold up the release.

[garrison]

To be clear, this issue is fixed on master with #12839. The remaining question is how to backport a fix for 0.4. Since #12839 no longer renames AsyncStream, is it possible/nonbreaking to do a straightforward backport to 0.4?

[tkelman]

I'll try putting it on a backport branch (probably after rc3 to avoid pushing that back any further) and evaluate whether it breaks anything via pkgeval

[garrison]

Sounds like a great plan. Thanks @tkelman!

[garrison]

Fixed in v0.4.0-rc4.