stack query generates a .cabal file as side effect #6780

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1. mpilgrem commented on Aug 7, 2025

   

   mpilgrem

   on Aug 7, 2025

   Last edited by mpilgrem

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   Yes, that is correct. stack query runs within a withBuildConfig withEnvConfig and like other similar Stack commands (for example stack build --dry-run) that involves configuring the build environment.

   Stepping back, what information is being sought? If it is not build information, then there may be a better 'home' for that functionality than stack query.
2. andreasabel commented on Aug 8, 2025

   

   andreasabel

   on Aug 8, 2025

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   Stepping back, what information is being sought?

   Yeah, I don't really know. This Powerlevel 10k prompt displays all kinds of useful information on the environment of the current directory (git branch name etc.), so I guess they thought, why not print the GHC version if there is a stack.yaml present in the project?

   That a command named query writes new files to the local directory must be very surprising to anyone who is not an implementer of stack.
   So I think there should be prominent alerts in the documentation and also in the help text:

   $ stack query --help                                                       
   Usage: stack query [SELECTOR...] [--setup-info-yaml URL] 
                      [--snapshot-location-base URL]
   
     Query general build information (experimental).
   
   Available options: ...
   

   The expected behavior of stack query compiler would be that it extracts the resolver/snapshot from the stack.yaml file, computes the ghc version from this and prints it.
   Apparently just a stack.yaml is not enough:

   $ stack query compiler                                                                                         
   
   Error: [S-636]
          Stack looks for packages in the directories configured in the packages and extra-deps fields defined in its project-level configuration file (usually
          stack.yaml). The current entry points to /Users/abela/tmp/stack-query-compiler-no-package-yaml/ but no Cabal file or package.yaml could be found there.
   

   I think at this point it might be enough to add the alert to the documentation, to make potential users of the stack query command aware of the consequences.
   I suppose the authors of the shell prompt would have refrained from adding a hook for stack if they had known about the consequences of running stack query.
3. mpilgrem commented on Aug 8, 2025

   

   mpilgrem

   on Aug 8, 2025

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   @andreasabel, there is a nuance to 'compiler' information: 'wanted' versus 'actual'. 'Wanted' is what is specified in the project-level configuration file and at the command line. 'Actual' is what is used. They can differ because of compiler-check options.

   A BuildConfig value has information about 'wanted' (via its smWanted field).

   A EnvConfig value also has information about 'actual' (via its sourceMap field).

   I think it would be straightforward to add a stack ls compiler command that output the 'wanted' compiler but did not configure the build environment.

   👍React with 👍1Reacted by Andreas Abel
4. andreasabel commented on Aug 9, 2025

   

   andreasabel

   on Aug 9, 2025

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   I think it would be straightforward to add a stack ls compiler command that output the 'wanted' compiler but did not configure the build environment.

   Good.
   I am not in a position to request this feature, though, as I do not have an application for it right now, and the "Powerlevel 10k" folks might not be actively developing their product anymore, given the disclaimer on their github repo.