Make snapshot: a synonym for resolver

[aleksejkozin]

• Any changes that could be relevant to users have been recorded in the ChangeLog.md
• The documentation has been updated, if necessary.

Fixing #4256

[aleksejkozin]

At this point I've added unit test

[aleksejkozin]

@snoyberg can you review my current code?

[mihaimaruseac]

Looks good. Add a line to documentation and then it's ready to merge.
thanks

[snoyberg]

Agreed with @mihaimaruseac, thanks!

[aleksejkozin]

@snoyberg as you mentioned in #4256

Implementation: in both snapshots and stack.yaml files

I'm not quite sure what the snapshots file is and how to use it. Could you please point me on a piece of documentation or code?

Also, there are multiple mentions of "resolver" in the source that I've missed before:

Config.hs

stack/src/Stack/Types/Config.hs

Line 625 in cc7e6cb

, ["resolver" .= resolver]

I'm not sure that if I rename it to "snapshot" everything will work fine. I can delete it without any test fail
What should I do?

Other files

ConfigCmd.hs
Freeze.hs
Init.hs
Options/ResolverParser.hs
Curator/Unpack.hs
Pantry/Types.hs

What should I do with them?

[snoyberg]

For snapshots files, this is what's known as "custom snapshots" and lives in the pantry part of the codebase. See:

https://github.com/commercialhaskell/stack/blob/master/doc/pantry.md

I believe that, for now, we should continue to use resolver when generating these files to keep better backwards compatibility. Therefore

• ConfigCmd: leave as-is
• Freeze: leave as-is
• Init: leave as-is
• ResolverParser: support --snapshot as well
• Unpack.hs: don't worry about the entire subs/curator subdir for now
• Pantry/Types: modify the FromJSON instance, but not the ToJSON instance

Does that make sense?

[aleksejkozin]

Does that make sense?

Partially, I still have a lot of questions 😃

1. I'm not sure what you meant by "ResolverParser: support --snapshot as well"
   Should I add the --snapshot support? If so, I don't know how to add a synonym to abstractResolverOptsParser, I think I should fix GlobalOptsMonoid but I don't know how
2. I don't know what to write about the FromJSON SnapshotLayer fix into ChangeLog.md
3. I'm not sure what to write into yaml_configuration.md
4. "resolver" mentions are scattered across all the documentation in different examples. Should I fix all if i? Make a search for resolver: in all .md files and replace mentions

[snoyberg]

1. Let's punt on this for now, we can figure it out later. It's definitely not needed immediately. For the record: I think you can use the alternative instance for the CLI parser to add support for "resolver" and "snapshot".
2. No changelog entries necessary in pantry, it's never been released. The changelog in Stack itself should be sufficient.
3. I can update the docs for you if you'd like, but it would be something like "Starting with Stack 2.0, snapshot is accepted as a synonym for resolver. Only one of these fields is permitted, not both."
4. Not yet, I'd say after some period of time of snapshot being supported we would take a pass at updating the docs.

[aleksejkozin]

Both Travis and AppVeyor builds has failed due to timeout, I don't know how to fix the issue

[snoyberg]

Looks like it passed this time. Even the Travis job that "failed" actually succeeded, it just didn't complete the cache upload. So I believe this is ready for final review. @mihaimaruseac did you want to do that, or would you like me to?

[mihaimaruseac]

Thanks

[aleksejkozin]

@mihaimaruseac thx for the reviews

This was my first code contribution to an open source project ever, I'm proud of myself 😄

I would be able to write better code for Stack if you guys would point on some of my weak points so I could work on them.
If you have some free time could you please answer:

• What one thing in the code I could write better?
• Were there any issues in our communication?

Thx!

[snoyberg]

I've never actually received that question on open source work before, I really appreciate your interest.

I'll give you a big communication strength: you pointed out when you were delayed, and then quite clearly pointed out problems you were having. It made it very easy to assist you.

I'm honestly very impressed with the code, and the fact that you included tests: many contributors don't do that. The only thing I'd recommend looking into is applicative parsers for CLI flags, so that you could more easily add --snapshot support on the command line on the future if desired.

I'd be very happy if you're interested in working on more issues. If you want any recommendations of good ones to onboard with, let me know.

[mihaimaruseac]

I second @snoyberg, this is the first time I see this, congrats.

From my point of view, all went perfect in handling this