stack new requires network to work

[vincenthz]

General summary/comments (optional)

without a network connection, stack new just fails to download a template, even though the template already exists in the template directory.

Expected

stack new try to download (update ? refresh cache ?) the template, but fallback to the existing template

 ls ~/.stack/templates/ -lh
total 8.0K
-rw-------. 1 user user 3.8K Feb  5 18:58 new-template.hsfiles
-rw-------. 1 user user   42 Feb  5 18:58 new-template.hsfiles.etag

Actual

$ stack new bla
Downloading template "new-template" to create project "bla" in bla/ ...

Warning: Retry number 0 after a total delay of 0 us
....
Warning: Retry number 3 after a total delay of 300000 us
         If you see this warning and stack fails to download, but running the command again solves the problem, please report here:
         https://github.com/commercialhaskell/stack/issues/3510
HttpExceptionRequest Request {
  host                 = "raw.githubusercontent.com"
  port                 = 443
  secure               = True
  requestHeaders       = [("If-None-Match","\"20199ac22a46c1b88a1e7e93f6555f4243430c44\"")]
  path                 = "/commercialhaskell/stack-templates/master/new-template.hsfiles"
  queryString          = ""
  method               = "GET"
  proxy                = Nothing
  rawBody              = False
  redirectCount        = 10
  responseTimeout      = ResponseTimeoutDefault
  requestVersion       = HTTP/1.1
}
 (ConnectionFailure Network.Socket.getAddrInfo: does not exist (Try again))

Stack version

$ stack --version
Version 1.6.3, Git revision b27e629b8c4ce369e3b8273f04db193b060000db (5454 commits) x86_64 hpack-0.20.0

[mgsloan]

👍 Agreed!

[sudsj]

Hi, I'm sort of a beginner to Haskell and since this issue was marked newcomer friendly I hope I can contribute. Can you @mgsloan @vincenthz give an overview of what has to be done, it would be helpful.

[mgsloan]

@sudsj Hi, sounds good! There are a few ways this could be implemented. I think it would be best to have it do the following:

• When downloading templates, always store in $STACK_ROOT/templates-cache. Should use Network.HTTP.Download.redownload. Then, load from the stored file.

• If that function throws RedownloadFailed, then display a message to the user that the download failed and the template might not be up-to-date. Then proceed to load it anyway from the stored file if one exists.

An alternative approach might be to have it clone the templates repo and attempt to do a fetch. This has some nice benefits, but would probably be more complicated. Up to you which approach is taken!

[BraulioVM]

Should this issue be closed now that #4173 got merged?

[mihaimaruseac]

That's true, closing. Thanks.