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The Stack 2 release represents a series of significant changes to how Stack works internally. For the vast majority of cases, these changes are backwards compatible, in that existing projects will continue to build in the same way with Stack 2 as they did with Stack 1. The large version bump is due to the fundamental internal changes to cache handling, database storage (using SQLite in place of binary files), implicit snapshots (which greatly improve the precompiled cache), and moving to Pantry. We have also removed some less used features, as listed in the release notes below.

See for installation and upgrade instructions.

Changes since v1.9.3

Major changes:

  • Switch over to pantry for managing packages. This is a major change
    to Stack's internals, and affects user-visible behavior in a few
    places. Some highlights:
    • Drop support for multiple package indices and legacy
      00-index.tar style indices. See
    • Support for archives and repos in the packages section has
      been removed. Instead, you must use extra-deps for such
      dependencies. packages now only supports local filepaths.
    • Add support for Git repositories containing (recursive) submodules.
    • Addition of new configuration options for specifying a "pantry
      tree" key, which provides more reproducibility around builds,
      and (in the future) will be used for more efficient package
      content downloads. You can also specify package name and version
      for more efficient config parsing.
      * NOTE The new stack freeze command provides support
      for automatically generating this additional
    • Package contents and metadata are stored in an SQLite database
      in place of files on the filesystem. The pantry library can be
      used for interacting with these contents.
    • Internally, Stack has changed many datatypes, including moving
      to Cabal's definition of many data types. As a result of such
      changes, existing cache files will in general be invalidated,
      resulting in Stack needing to rebuild many previously cached
      builds in the new version. Sorry :(.
    • A new command, stack freeze has been added which outputs
      project and snapshot definitions with dependencies pinned to
      their exact versions.
    • The ignore-revision-mismatch setting is no longer needed, and
      has been removed.
    • Overriding GHC boot packages results in any other GHC boot
      packages depending on it being no longer available as a dependency,
      such packages need to be added explicitly when needed. See
      [#4510] (#4510).
    • Cabal solver integration was not updated to support newer
      cabal-install versions so stack solver command was removed as
      well as a related option --solver from stack new and
      stack init.
  • Upgrade to Cabal 2.4
    • Note that, in this process, the behavior of file globbing has
      been modified to match that of Cabal. In particular, this means
      that for Cabal spec versions less than 2.4, *.txt will
      match foo.txt, but not foo.2.txt.
  • Remove the stack image command. With the advent of Docker multistage
    builds, this functionality is no longer useful. For an example, please see
    Building Haskell Apps with
  • Support building GHC from source (experimental)
    • Stack now supports building and installing GHC from source. The built GHC
      is uniquely identified by a commit id and an Hadrian "flavour" (Hadrian is
      the newer GHC build system), hence compiler can be set to use a GHC
      built from source with ghc-git-COMMIT-FLAVOUR
  • stack.yaml now supports a configure-options, which are passed directly to
    the configure step in the Cabal build process. See
  • Remove support for building GHCJS itself. Future releases of Stack
    may remove GHCJS support entirely.
  • Support for lock files for pinning exact project dependency versions

Behavior changes:

  • stack.yaml now supports snapshot: a synonym for resolver. See
  • stack script now passes -i -idir in to the ghc
    invocation. This makes it so that the script can import local
    modules, and fixes an issue where .hs files in the current
    directory could affect interpretation of the script. See
  • When using stack script, custom snapshot files will be resolved
    relative to the directory containing the script.
  • Remove the deprecated --upgrade-cabal flag to stack setup.
  • Support the drop-packages field in stack.yaml
  • Remove the GPG signing code during uploads. The GPG signatures have
    never been used yet, and there are no plans to implement signature
  • Remove the --plain option for the exec family of commands
  • Always use the --exact-configuration Cabal configuration option when
    building (should mostly be a non-user-visible enhancement).
  • No longer supports Cabal versions older than 1.19.2. This means
    projects using snapshots earlier than lts-3.0 or
    nightly-2015-05-05 will no longer build.
  • Remove the stack docker cleanup command. Docker itself now has
    docker image prune
    docker container prune,
    which you can use instead.
  • Interleaved output is now turned on by default, see
    #4702. In
    addition, the packagename> prefix is no longer included in
    interelaved mode when only building a single target.
  • The -fhide-source-paths GHC option is now enabled by default and
    can be disabled via the hide-source-paths configuration option in
    stack.yaml. See #3784
  • Stack will reconfigure a package if you modify your PATH environment
    variable. See
  • For GHC 8.4 and later, disable the "shadowed dependencies" workaround. This
    means that Stack will no longer have to force reconfigures as often. See
  • When building a package, Stack takes a lock on the dist directory in
    use to avoid multiple runs of Stack from trampling each others'
    files. See
  • Stack will check occassionally if there is a new version available and prompt
    the user to upgrade. This will not incur any additional network traffic, as
    it will piggy-back on the existing Hackage index updates. You can set
    recommend-stack-upgrade: false to bypass this. See
  • stack list-dependencies has been removed in favour of stack ls dependencies.
  • The new default for --docker-auto-pull is enabled. See

Other enhancements:

  • Support MX Linux in Fixes
  • Defer loading up of files for local packages. This allows us to get
    plan construction errors much faster, and avoid some unnecessary
    work when only building a subset of packages. This is especially
    useful for the curator use case.
  • Existing global option --color=WHEN is now also available as a
    non-project-specific yaml configuration parameter color:.
  • Adopt the standard proposed at, that color should not be
    added by default if the NO_COLOR environment variable is present.
  • New command stack ls stack-colors lists the styles and the associated 'ANSI'
    control character sequences that stack uses to color some of its output. See
    stack ls stack-colors --help for more information.
  • New global option --stack-colors=STYLES, also available as a
    non-project-specific yaml configuration parameter, allows a stack user to
    redefine the default styles that stack uses to color some of its output. See
    stack --help for more information.
  • British English spelling of 'color' (colour) accepted as an alias for
    --color, --stack-colors, stack ls stack-colors at the command line and
    for color: and stack-colors: in yaml configuration files.
  • New build option --ddump-dir. (See
  • Stack parses and respects the preferred-versions information from
    Hackage for choosing latest version of a package in some cases,
    e.g. stack unpack packagename.
  • The components output in the The main module to load is ambiguous message
    now include package names so they can be more easily copy-pasted.
  • Git repos are shared across multiple projects. See
  • Use en_US.UTF-8 locale by default in pure Nix mode so programs won't
    crash because of Unicode in their output
  • Add --tree to ls dependencies to list dependencies as tree.
  • Add --pedantic to ghci to run with -Wall and -Werror
  • Add --cabal-files flag to stack ide targets command.
  • Add --stdout flag to all stack ide subcommands.
  • Use batches when unregistering packages with ghc-pkg.
    (See #2662)
  • get-stack script now works on Windows CI machines of Appveyor,
    Travis and Azure Pipelines. See
  • Show snapshot being used when stack ghci is invoked outside of a project
    directory. See
  • The script interpreter now accepts a --extra-dep flag for adding
    packages not present in the snapshot. Currently, this only works
    with packages from Hackage, not Git repos or archives.
  • When using the script interpreter with --optimize or --compile,
    Stack will perform an optimization of checking whether a newer
    executable exists, making reruns significantly faster. There's a
    downside to this, however: if you have a multifile script, and
    change one of the dependency modules, Stack will not automatically
    detect and recompile.
  • stack clean will delete the entire .stack-work/dist directory,
    not just the relevant subdirectory for the current GHC version. See
  • Add stack purge as a shortcut for stack clean --full. See
  • Both stack dot and stack ls dependencies accept a
    --global-hints flag to bypass the need for an installed GHC. See
  • Add the stack config env command for getting shell script environment
    variables. See #620.
  • Less verbose output from stack setup on Windows. See
  • Add an optional ignore-expiry flag to the hackage-security
    section of the ~/.stack/config.yaml. It allows to disable timestamp
    expiration verification just like cabal --ignore-expiry does.
    The flag is not enabled by default so that the default functionality
    is not changed.
  • Include default values for most command line flags in the --help
    output. See
  • Set the GHC_ENVIRONMENT environment variable to specify dependency
    packages explicitly when running test. This is done to prevent
    ambiguous module name errors in doctest tests.
  • get-stack script now works on Windows CI machines of Appveyor,
    Travis and Azure Pipelines. See
  • Warn when a Docker image does not include a PATH environment
    variable. See
  • When using system-ghc: true, Stack will now find the appropriate GHC
    installation based on the version suffix, allowing you to more easily switch
    between various system-installed GHCs. See
  • stack init will now support create a stack.yaml file without any local
    packages. See #2465
  • Store caches in SQLite database instead of files.
  • No longer use "global" Docker image database (docker.db).
  • User config files are respected for the script command. See
  • Set the GHC_ENVIRONMENT environment variable to - to tell GHC to
    ignore any such files when GHC is new enough (>= 8.4.4), otherwise
    simply unset the variable. This allows Stack to have control of
    package databases when running commands like stack exec ghci, even
    in the presence of implicit environment files created by cabal new-build. See
  • Use a database cache table to speed up discovery of installed GHCs
  • You can specify multiple --test-arguments options. See
  • Windows terminal width detection is now done. See
  • On Windows, informs users if the 'programs' path contains a space character
    and further warns users if that path does not have an alternative short
    ('8 dot 3') name, referencing the local-programs-path configuration option.
    See #4726
  • Add --docker-mount-mode option to set the Docker volume mount mode
    for performance tuning on macOS.

Bug fixes:

  • Ignore duplicate files for a single module when a Haskell module was
    generated from a preprocessor file. See
  • Only track down components in current directory if there are no
    hs-source-dirs found. This eliminates a number of false-positive
    warnings, similar to
  • Handle a change in GHC's hi-dump format around addDependentFile,
    which now includes a hash. See
  • Fix subdirs for git repos in extra-deps to match whole directory names.
    Also fixes for subdirs: .. See
  • Fix for git packages to update submodules to the correct state. See
  • Add --cabal-files flag to stack ide targets command.
  • Don't download ghc when using stack clean.
  • Support loading in GHCi definitions from symlinked C files. Without this
    patch, Stack will try to find object files in the directory pointed to
    by symlinks, while GCC will produce the object files in the original
    directory. See
  • Fix handling of GitHub and URL templates on Windows. See
  • Fix --file-watch not responding to file modifications when running
    inside docker on Mac. See
  • Using --ghc-options with stack script --compile now works.
  • Ensure the detailed-0.9 type tests work.
    See #4453.
  • Extra include and lib dirs are now order-dependent. See
  • Apply GHC options when building a Setup.hs file. See
  • Stack handles ABI changes in FreeBSD 12 by differentiating that version from
  • Help text for the templates subcommand now reflects behaviour in stack 1.9
    — that it downloads and shows a help file, rather than listing available
  • Fix detection of aarch64 platform (this broke when we upgraded to a newer
    Cabal version).
  • Docker: fix detecting and pulling missing images with --docker-auto-pull, see
  • Hackage credentials are not world-readable. See
  • Warnings are dumped from logs even when color is enabled. See
  • stack init will now work for cabal files with sublibraries. See
  • When the Cabal spec version is newer than the global Cabal version, build
    against the snapshot's Cabal library. See
  • Docker: fix detection of expected subprocess failures. This fixes
    downloading a compatible stack executable when the host stack is not
    compatible with the Docker image (on Linux), and doesn't show an unnecessary
    extra error when the in-container re-exec'ed stack exits with failure.
  • The stack ghci command's --ghc-options flag now parses multiple options.
    See #3315.

Thanks to all our contributors for this release:

  • Adam Bergmark
  • Akshay Mankar
  • Aleksey Kozin
  • ALeX Kazik
  • Alexey Kozin
  • Alexey Kuleshevich
  • Anders Kaseorg
  • Anders Kiel Hovgaard
  • Artyom Kazak
  • Bastian Krol
  • Björn Gohla
  • Brad Neimann
  • Brandon Chinn
  • Colin Woodbury
  • Cthulhu.Den
  • dadepo
  • Daniel Gröber
  • David Baynard
  • David Spies
  • David Vollbracht
  • dbaynard
  • Emanuel Borsboom
  • favonia
  • flip111
  • Florjan Bartol
  • Gleb Popov
  • Hussein Ait-Lahcen
  • Isumi Feng
  • Janfel
  • Jurijs Oniscuks
  • Kayla Ngan
  • Kirill Zaborsky
  • Magicloud
  • Matt Audesse
  • Mauricio Fierro
  • Michael Sloan
  • Michael Snoyman
  • Mihai Maruseac
  • Mike Pilgrem
  • Neil Mitchell
  • NeonGraal
  • Niklas Hambüchen
  • penteract
  • Phil de Joux
  • Raghu Kaippully
  • Sibi
  • Sibi Prabakaran
  • Simon Hengel
  • skapazzo
  • Sylvain HENRY
  • Sylvain Henry
  • Taekyung
  • Timothy Clem
  • Tom Sydney Kerckhove
  • Valery V. Vorotyntsev
  • Vance Palacio
  • waddlaw
  • 欧阳泽