REPL command in project requires a target #10684

philderbeast · 2024-12-28T13:20:47Z

Fixes #10527 and #9983. Depend-on: #10688.

Doesn't allow an empty list of targets with a project context.

With a project, the REPL command requires a target. If one is not given then a message is shown explaining this and naming the project if the --project-file option was given (but not when the default 'cabal.project' project name is used implicitly). ~~We're not yet able to list project targets so in the meantime, the messages lists the packages of the project.~~

When the implicit default cabal.project is used:

$ cat cabal.project
packages: pkg-one pkg-two

$ cabal repl
Error: [Cabal-7076]
With a project, the REPL command requires a single target. The packages in this
project are:
 - pkg-one
 - pkg-two

When the --project-file option is used, the file name is included:

$ cat some.project 
packages: pkg-one pkg-two

$ cabal repl --project-file=some.project
...
Error: [Cabal-7076]
With a project, the REPL command requires a single target. The packages in this
project, 'some.project', are:
 - pkg-one
 - pkg-two

When the project has no packages, this is mentioned in the message:

$ cat empty.project

$ cabal repl --project-file=empty.project
...
Error: [Cabal-7076]
There are no packages in 'empty.project'. Please add a package to the project and pick a
single [package:][ctype:]component as target for the REPL command.

Before the fix the message mentioned a fake-package-0. This was confusing:

$ ~/.ghcup/bin/cabal-3.12.1.0 repl --project-file=some.project
...
Error: [Cabal-7076]
Internal error when trying to open a repl for the package fake-package-0. The
package is not in the set of available targets for the project plan, which would
suggest an inconsistency between readTargetSelectors and resolveTargets.

Earlier cabal-install:exe:cabal versions mentioned using all as the target but this won't work for the REPL command:

$ ~/.ghcup/bin/cabal-3.10.3.0 repl --project-file=some.project
Error: cabal-3.10.3.0: No targets given and there is no package in the current
directory. Use the target 'all' for all packages in the project or specify
packages or components by name or location. See 'cabal build --help' for more
details on target options.

Patches conform to the coding conventions.
Any changes that could be relevant to users have been recorded in the changelog.
- Is the change significant? If so, remember to add significance: significant in the changelog file.
The documentation has been updated, if necessary.
Manual QA notes have been included.
Tests have been added.

philderbeast · 2025-06-16T20:04:19Z

This pull request will be easier to review once the cfgVerbosity changes are merged.

geekosaur

Approving despite suggestions because they're not functional changes.

cabal-install/src/Distribution/Client/CmdRepl.hs

changelog.d/pr-10684.md

cabal-install/src/Distribution/Client/CmdRepl.hs

ulysses4ever

Thanks for this patch and the test! I have a couple questions...

@mpickering could you take a brief look at this (it's a small patch)? Especially my comment under the -- NOTE:.

changelog.d/pr-10684.md

cabal-install/src/Distribution/Client/CmdRepl.hs

ulysses4ever · 2025-06-18T17:47:44Z

cabal-install/src/Distribution/Client/CmdRepl.hs

+                    text "There are no packages in"
+                      <+> (project <> char '.')
+                      <+> text "Please add a package to the project and pick a component to use as the target of the REPL command."


the no-packages case is certainly already handled in other places today, right? (people keep forgetting packages:... and get an error message.) Is it possible to not duplicate this logic?

After removing the target string manipulation, the current behaviour (#9983) is bad and doesn't cover this case:

$ ~/.ghcup/bin/cabal --numeric-version 3.14.2.0 $ ~/.ghcup/bin/cabal repl --project-dir=cabal-testsuite/PackageTests/ReplProjectTarget --project-file=empty.project Configuration is affected by the following files: - empty.project Warning: There are no packages or optional-packages in the project Resolving dependencies... Error: [Cabal-7076] Internal error when trying to open a repl for the package fake-package-0. The package is not in the set of available targets for the project plan, which would suggest an inconsistency between readTargetSelectors and resolveTargets.

Also I'd be curious to know how to get better output from a debug build of cabal-install with assertions enabled because that version gives me a poorer error report with no line number:

$ cabal repl --project-dir=cabal-testsuite/PackageTests/ReplProjectTarget --project-file=empty.project Warning: this is a debug build of cabal-install with assertions enabled. Configuration is affected by the following files: - empty.project Warning: There are no packages or optional-packages in the project Resolving dependencies... Assertion failed

Warning: There are no packages or optional-packages in the project

is a different issue, I think, (#8679 probably) so it may be wise to try to avoid solving it here.

assertion failure is bad but also looks like a future work. We're minutes from cutting the 3.16 branch and all backporting will have to go through extra careful consideration (mostly deciding the tradeoff: scarse resource for the release vs profit from performing the backport)

The assertion bothers me. I could cut back on the scope of this pull request or dig in more about the assertion.

the no-packages case is certainly already handled in other places today, right? (people keep forgetting packages:... and get an error message.) Is it possible to not duplicate this logic?

@ulysses4ever, it is handled elsewhere but as a warning:

cabal/cabal-install/src/Distribution/Client/ProjectOrchestration.hs

Lines 312 to 314 in 27593dc

-- https://github.com/haskell/cabal/issues/6013

when (null (projectPackages projectConfig) && null (projectPackagesOptional projectConfig)) $

warn verbosity "There are no packages or optional-packages in the project"

So in the meantime (as I'm not suppressing the warning) we get both a warning and an error:

$ cabal repl --project-file=empty.project Warning: this is a debug build of cabal-install with assertions enabled. Warning: There are no packages or optional-packages in the project Error: [Cabal-7076] There are no packages in 'empty.project'. Please add a package to the project and pick a single [package:][ctype:]component as target for the REPL command.

Given the warning (unless there's already some way to suppress it, shouldn't the error message change to be a follow-on to it?

I'm OK with the warning and then the error. Scolding, I warned you and now look what has happened, an error!

I feel the better way to fix this would be to suppress the warning.

ulysses4ever · 2025-07-29T20:00:36Z

Cool, thanks! Let's see what CI says.

Any chance you could squash some of those commits?

philderbeast · 2025-07-30T11:12:02Z

I missed updating a test. The update in the test output is:

$ git diff
...
 # checking repl command with an 'empty.project' with no packages
 # cabal repl
 Warning: There are no packages or optional-packages in the project
-Resolving dependencies...
+Error: [Cabal-7076]
+There are no packages in 'empty.project'. Please add a package to the project and pick a
+ single [package:][ctype:]component as target for the REPL command.

cabal-testsuite/PackageTests/ReplProjectNoneTarget/cabal.test.hs

cabal-install/src/Distribution/Client/CmdRepl.hs

mpickering · 2025-08-05T09:01:36Z

I'm struggling a bit to do a proper review without diving in and understanding all the details myself. So I am also happy to merge what you have done already (with the error message comment modified) and we can improve it later if necessary.

It seems that there is some awkwardness around the fact that

In a project context you have to specify a target
In other contexts you don't have to specify a target

This leads to passing AcceptNoTargets to withContextAndSelectors, and then having to check whether there are no targets in the ProjectContext case.

Perhaps another design would be to make withContextAndSelectors take a function TargetContext -> AcceptNoTargets? Did you consider doing that?

I suppose resolveTargets is not suitable here since that is dealing with resolving what a target string is referring to (in this case there isn't a target string).

philderbeast · 2025-08-07T20:29:27Z

Sorry @mpickering for roping you in for an premature review. I couldn't see how to cancel a "re-request review". Thanks for the feedback. I sought early feedback given the urgency of #11107.

cabal-install/src/Distribution/Client/CmdRepl.hs

philderbeast · 2025-08-08T01:55:27Z

It seems that there is some awkwardness around the fact that

In a project context you have to specify a target

In other contexts you don't have to specify a target

I'm making one exception here, picking the package as the target when a project has but one package and no targets are given.

- Show packages when no --project-file is given - Handle the case with no packages in the project - Add a changelog - Add tests - Satisfy hlint - Satisfy fourmolu - Don't need a target when there is one package - Adjust target strings for sole package - Add alt.project tests for ReplOptions - Silence the 1st withCtx call's verbosity - Don't repeat configuration is affected by - Satisfy whitespace - Fixups after rebase - Remove punct variable

- Comma with but joining indep' clauses - Use single package Co-Authored-By: brandon s allbery kf8nh <[email protected]>

- Improve test descriptions - Mention [package:][ctype:]component - Don't repeat [package:][ctype:]component - Lift validatedTargets, rename r as replFlags - Don't use -XRecordWildCards for configFlags - Add a one.project one pkg test - Remove target string manipulation - Make reportProjectNoTarget a function - Redo ReplProjectTarget tests - Redo ReplProjectNoneTarget tests - Satisfy fix-whitespace - Error whether or not project has packages - Guard against triggering an assertion if targets are null

ulysses4ever · 2025-09-29T18:48:49Z

@mpickering could you take another look at this? it'd be great to have it in for 3.16.1.0...

philderbeast marked this pull request as draft December 28, 2024 13:20

philderbeast force-pushed the fix/repl-project-null-target branch 4 times, most recently from 09fcf06 to 6dd178f Compare December 28, 2024 16:31

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philderbeast added attention: needs-review cabal-install: cmd/repl labels Dec 28, 2024

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philderbeast mentioned this pull request Jun 16, 2025

Add cfgVerbosity #10688

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make cabal less chatty w.r.t. project files in use #10940

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Review comment changes

e9d4b5a

- Comma with but joining indep' clauses - Use single package Co-Authored-By: brandon s allbery kf8nh <[email protected]>

Skip if Windows

e5107b7

Repl commands mentioning the fake-package

25eb01e

- Don't yet automatically pick only choice

3370f7b

Autopick the one package

1af4c8c

Split ReplProjectTarget test

3eb9d8c

Add tests for repl all target

56540bd

Also hint that the "all" target can be used

ffa5e9c

philderbeast force-pushed the fix/repl-project-null-target branch from a3d1535 to ffa5e9c Compare August 11, 2025 17:45

	-- https://github.com/haskell/cabal/issues/6013
	when (null (projectPackages projectConfig) && null (projectPackagesOptional projectConfig)) $
	warn verbosity "There are no packages or optional-packages in the project"

REPL command in project requires a target #10684

Are you sure you want to change the base?

REPL command in project requires a target #10684

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