Unexpected import (implicit) Prelude code lens

[konsumlamm]

Example

I'm not sure if the import (implicit) Prelude code lens itself supposed to be a feature or not, but the import code lens for the module isn't shown. When a newline is added before, this doesn't occur:

GHC version: 9.2.2
HLS version: 1.7.0.0

[fendor]

Thank you for the bug report! Moving to HLS repo where this feature is implemented

[drsooch]

Any extra information on this? HLS version? GHC version? Project details (are you using some non-standard setup)?

I tried to repro with a simple file but didn't see anything.

[konsumlamm]

Sorry, I edited the issue to include the GHC and HLS versions. There is no non-standard setup, just a simple default setup (generated by cabal init).

[drsooch]

Looks like this just affects GHC 9.2.*

[sloorush]

I tried to reproduce the error, and it is reproducible.

The import (implicit) Prelude () text comes up when the import statement is in the first list of the file. Here is a screenshot comparing the two situations:

Testing on ghc-9.2.2, this was not reproducible on ghc-9.0.2

[ChristophHochrainer]

Hey, I could also reproduce it and I believe to have found the culprit.

I believe it is the function minimalImportsRule inside plugins/hls-explicit-imports-plugin/src/Ide/Plugin/ExplicitImports.hs, or more specifically the importsMap.

let importsMap =
        Map.fromList
          [ (realSrcSpanStart l, printOutputable i)
            | L (locA -> RealSrcSpan l _) i <- fromMaybe [] mbMinImports
          ]
      res =
        [ (i, Map.lookup (realSrcSpanStart l) importsMap)
          | i <- imports
          , RealSrcSpan l _ <- [getLoc i]
        ]

This map uses the source location as key and only allows a single value and not a value list. The GHC API always gives the import (implicit) Prelude suggestion in the first line. So every other import in the first line collides with this and gets overridden. A solution to this could be exclude the Prelude code action.