Library and utility for processing cabal's plan.json file

LTS Haskell 22.26:
Stackage Nightly 2024-06-18:
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GPL-2.0-or-later licensed by Herbert Valerio Riedel
Maintained by [email protected]
This version can be pinned in stack with:cabal-plan-,5286

Module documentation for

This package provides a library (see Cabal.Plan) for decoding plan.json files as well as the simple tool cabal-plan for extracting and pretty printing the information contained in the plan.json file.

plan.json files are generated by cabal's Nix-style local builds and contain detailed information about the build/install plan computed by the cabal solver.

cabal-plan utility

The cabal-plan executable (enabled via the exe cabal flag) provides various operations:

Show basic report of dependency tree
Dump PlanJson data-structure via Show instance
Show dependency tree as a graph
Diff two install plans
List all binaries
List single binary (useful for scripting, e.g. cabal list-bin exe:cabal-plan)
Print SHA256 sums of dependencies' source tarballs and cabal files
Generate graph of dependencies in .dot format
Print plan topologically sorted
Generate license report for a component (only available when built with license-report flag enabled); see report example for cabal-plan (Pandoc rendered HTML)

See also "New things in Haskell package QA" Blogpost for a description of the topo and dot operations as well as how to enable tab-completion.


Revision history for cabal-plan

  • Use Cabal-syntax-3.12
  • Support GHC-8.6.5…9.10.1

  • Use Cabal-syntax-3.10

  • Fix issue in previous release (license generation didn’t work at all)

  • Use Cabal-syntax-

  • Support Cabal-3.6
  • Support aeson-
  • Drop support for GHC prior 8.2

exe:cabal-plan Executable

  • Use cabal-install-parsers to find and parse ~/cabal/config
  • Fix ascii/unicode output in tred
  • Add flags to hide setup and executable components in dot command
  • Update dependencies (support base16-bytestring-


  • Update dependencies (support base16-bytestring-

exe:cabal-plan Executable

  • Add --ascii / --unicode flags to control output character set
  • Add dot-png command as a version of dot command with different defaults
  • Use cabal-install-parsers, this makes license-report work with non-default configurations

lib:cabal-plan Library

  • Support local+noindex style repositories: New Repo constructor: RepoLocalNoIndex.
  • Support newer versions of dependencies (GHC-8.10, aeson-1.5, optics-core-0.3)

exe:cabal-plan Executable

  • Support Cabal-3.2

lib:cabal-plan Library

  • Add findPlanJson function

exe:cabal-plan Executable

  • Drop process-extras dependency

lib:cabal-plan Library

No changes

exe:cabal-plan Executable

  • dot command got new options

    • --root to limit graph to specific roots
    • --output to write directly to some file
    • --run-dot-png and --run-dot-pdf to run dot for you
  • cabal-plan executable depends on optics-core instead of lens. Therefore is buildable only with GHC-8.0+

lib:cabal-plan Library

  • ExactPath constructor to skip find in findAndDecodePlanJson. (Note: see also decodePlanJson)

exe:cabal-plan Executable

  • --plan-json for exact plan.json location
  • --relative search for project root relative to that directory
  • --colors=auto|never|always flag
  • tred command to print transtive reduction of dependency graph
  • diff command to compare two plans
  • list-bins prints full selector “pkg:type:name”, i.e. includes package name

lib:cabal-plan Library

  • New dispCompNameTarget function for pretty-printing CompNames in cabal’s target-selector syntax.
  • Add support for cabal 2.4’s pkg-src package provenience metadata.
  • Add support for cabal 2.4.1’s pkg-cabal-sha256 package description checksum field.

exe:cabal-plan Executable

  • Add support for including package description checksums in fingerprint output
  • Add support for printing flag selection in topo output
  • Fail gracefully in license-report when metadata cannot be found in index

lib:cabal-plan Library

  • New SearchPlanJson type to specify strategy for locating plan.json
  • Add SearchPlanJson parameter to findAndDecodePlanJson function and change return type
  • Expose separate findProjectRoot operation

exe:cabal-plan Executable

  • New command license-report (requires Cabal flag license-report to be active)

lib:cabal-plan Library

  • Add support for foreign-lib components.
  • Add support for dist-dir plan.json field.
  • Make Sha256 type abstract and add new sha256{To,From}ByteString conversion functions, as well as the new parseSha256 function.
  • Introduce FlagName newtype.
  • Add FromJSONKey/ToJSONKey instances for UnitId, PackageName, and PkgId.

exe:cabal-plan Executable

  • smart completer for list-bin/list-bins pattern
  • new command topo (printing out topographic sorting of install-plan)
  • dot prints component dependency graph. New options:
    • --tred transitive reduction
    • --tred-weights Adjust edge thickness during transitive reduction
    • --path-from pkgA --path-from pkgB Highlight dependency paths from pkgA to pkgB
    • --revdep pkg highlight reverse dependencies of pkg in the install plan

  • Add an optional --builddir argument to all commands and to findAndDecodePlanJson function.
  • Add experimental support for underlining.
  • Reimplement CLI with optparse-applicative.
  • Add new sub-command list-bins and change semantics of existing list-bin sub-cmd.

  • Add cabal-plan fingerprint command for printing sha256 sums of source tarballs.

  • First version. Released on an unsuspecting world.