Make snapshot: a synonym for resolver:

[snoyberg]

I discussed this already on Twitter. Basic idea: resolver turns out to have not been a great name. That field is used for specifying a snapshot. Let's just call a spade a spade.

Implementation: in both snapshots and stack.yaml files, instead of looking for just resolver, we'll look for both resolver and snapshot. If both are present: it's an error. If one is present, use it. If neither are present, follow through with current behavior for when there's no resolver set.

[DanBurton]

Also: update stack new templates to prefer snapshot.

Does stack have any philosophy regarding deprecation? Should support for resolver eventually be removed?

[snoyberg]

We don't have an official policy. In the past, we've:

• Added a warning on the old syntax
• Left it in for a few versions
• Removed support for the old syntax

[aleksejkozin]

Hi, guys!
I'm a new at Haskell, but already appreciate Stack a lot
I want to help you with this task
Is it free to take?
Is it a good place to start?

[snoyberg]

Yes to both questions! The best place to start would be to grep the src directory for the string "resolver". The most important affected module is Stack.Types.Config.

[aleksejkozin]

Guys, I'm sorry for the delay
For the last two weeks I hadn't had consistent working time due to personal circumstances
I still want to finish this issue, but I need more time, week or two

[snoyberg]

No worries, thanks for the update.

[aleksejkozin]

@snoyberg can you tell me if I'm thinking in the right direction?

I want to add snapshot support into stack.yaml
To achieve it I want to amend a function parseProjectAndConfigMonoid (because it contains "resolver"):

stack/src/Stack/Types/Config.hs

Line 1452 in cf9b94d

parseProjectAndConfigMonoid :: Path Abs Dir -> Value -> Yaml.Parser (WithJSONWarnings (IO ProjectAndConfigMonoid))

My plan is:

• add several unit tests to ConfigSpec.hs
  describe "parseProjectAndConfigMonoid"
it "parses snapshot using 'resolver'"
it "parses snapshot using 'snapshot'"
it "throws if both 'resolver' and 'snapshot' are present"
• write actual code so the tests will pass

For now I'm thinking of how to write the tests:
I want to create a temp predefined stack.yaml and load it with parseProjectAndConfigMonoid
It will give me Project object from which I can get projectResolver :: SnapshotLocation
After that I will check if projectResolver is equal to a correct value

If that is a correct line of thought then I have a question:
My stack.yaml is

 resolver: lts-2.10
 packages: ['.']

How can I do something like

projectResolver `shouldBe` "lts-2.10"

in a test?
SnapshotLocation and String types are incomparable

[snoyberg]

Overall that sounds right. I'm not quite sure what "temp predefined stack.yaml" means.

For the unit test, you're going to have to construct a SnapshotLocation value. You can use the ltsSnapshotLocation and nightlySnapshotLocation functions from pantry for LTS and nightly snapshots, and the SLCompiler data constructor for ghc-8.4.3 style snapshots.

[aleksejkozin]

I'm not quite sure what "temp predefined stack.yaml" means.

I was trying to say that I will copy workflow of loadConfig tests:

• changing working directory on a temp dir using inTempDir
• creating stack.yaml file with content of a string constant defined in ConfigSpec.hs
• loading data from the file and verifying it

For the unit test, you're going to have to construct a SnapshotLocation value. You can use the ltsSnapshotLocation and nightlySnapshotLocation functions from pantry for LTS and nightly snapshots, and the SLCompiler data constructor for ghc-8.4.3 style snapshots.

Thx for your help, it was useful!

[mihaimaruseac]

Closed by #4341