YAML Configuration

This page is intended to fully document all configuration options available in the stack.yaml file. Note that this page is likely to be both incomplete and sometimes inaccurate. If you see such cases, please update the page, and if you're not sure how, open an issue labeled "question".

The stack.yaml configuration options break down into project-specific options in:

  • <project dir>/stack.yaml

and non-project-specific options in:

  • /etc/stack/config.yaml -- for system global non-project default options
  • ~/.stack/config.yaml -- for user non-project default options
  • The project file itself may also contain non-project specific options

Note: When stack is invoked outside a stack project it will source project specific options from ~/.stack/global/stack.yaml. Options in this file will be ignored for a project with its own <project dir>/stack.yaml.

Project-specific config

Project-specific options are only valid in the stack.yaml file local to a project, not in the user or global config files.

Note: We define project to mean a directory that contains a stack.yaml file, which specifies how to build a set of packages. We define package to be a package with a .cabal file.

In your project-specific options, you specify both which local packages to build and which dependencies to use when building these packages. Unlike the user's local packages, these dependencies aren't built by default. They only get built when needed.

Shadowing semantics, described here, are applied to your configuration. So, if you add a package to your packages list, it will be used even if you're using a snapshot that specifies a particular version. Similarly, extra-deps will shadow the version specified in the resolver.

packages

The packages section lists all local (project) packages. The term local package should be differentiated from a dependency package. A local package is something that you are developing as part of the project. Whereas a dependency package is an external package that your project depends on.

In its simplest usage, it will be a list of directories or HTTP(S) URLs to a tarball or a zip. For example:

packages:
  - .
  - dir1/dir2
  - https://example.com/foo/bar/baz-0.0.2.tar.gz

Each package directory or location specified must have a valid cabal file present. Note that the subdirectories of the directory are not searched for cabal files. Subdirectories will have to be specified as independent items in the list of packages.

When the packages field is not present, it defaults to looking for a package in the project's root directory:

packages:
  - .

Complex package locations (location)

More complex package locations can be specified in a key-value format with location as a mandatory key. In addition to location some optional key-value pairs can be specified to include specific subdirectories or to specify package attributes as descibed later in this section.

In its simplest form a location key can have a single value in the same way as described above for single value items. Alternativel it can have key-value pairs as subfields to describe a git or mercurial repository location. For example:

packages:
- location: .
- location: dir1/dir2
- location: https://example.com/foo/bar/baz-0.0.2.tar.gz
- location: http://github.com/yesodweb/wai/archive/2f8a8e1b771829f4a8a77c0111352ce45a14c30f.zip
- location:
    git: git@github.com:commercialhaskell/stack.git
    commit: 6a86ee32e5b869a877151f74064572225e1a0398
- location:
    hg: https://example.com/hg/repo
    commit: da39a3ee5e6b4b0d3255bfef95601890afd80709

Note: it is highly recommended that you only use SHA1 values for a Git or Mercurial commit. Other values may work, but they are not officially supported, and may result in unexpected behavior (namely, stack will not automatically pull to update to new versions).

A location key can be accompanied by a subdirs key to look for cabal files in a list of subdirectories as well in addition to the top level directory.

This could be useful for mega-repos like wai or digestive-functors.

The subdirs key can have multiple nested series items specifying a list of subdirectories. For example:

packages:
- location: .
  subdirs:
  - subdir1
  - subdir2
- location:
    git: git@github.com:yesodweb/wai
    commit: 2f8a8e1b771829f4a8a77c0111352ce45a14c30f
  subdirs:
  - auto-update
  - wai
- location: http://github.com/yesodweb/wai/archive/2f8a8e1b771829f4a8a77c0111352ce45a14c30f.zip
  subdirs:
  - auto-update
  - wai

Local dependency packages (extra-dep)

A location key can be accompanied by an extra-dep key. When the extra-dep key is set to true it indicates that the package should be treated in the same way as a dependency package and not as part of the project. This means the following: A dependency package is built only if a user package or its dependencies depend on it. Note that a regular project package is built anyway even if no other package depends on it. Its test suites and benchmarks will not be run. * It will not be directly loaded in ghci when stack ghci is run. This is important because if you specify huge dependencies as project packages then ghci will have a nightmare loading everything.

This is especially useful when you are tweaking upstream packages or want to use latest versions of the upstream packages which are not yet on Hackage or Stackage.

For example:

packages:
- location: .
- location: vendor/binary
  extra-dep: true
- location:
    git: git@github.com:yesodweb/wai
    commit: 2f8a8e1b771829f4a8a77c0111352ce45a14c30f
  subdirs:
  - auto-update
  - wai
  extra-dep: true

extra-deps

This is a list of package identifiers for additional packages from upstream to be included. This is usually used to augment an LTS Haskell or Stackage Nightly snapshot with a package that is not present or is at an different version than you wish to use.

extra-deps:
- acme-missiles-0.3

Note that the extra-dep attribute in the packages section as described in an earlier section is used for non-index local or remote packages while the extra-deps section is for packages to be automatically pulled from an index like Hackage.

resolver

Specifies how dependencies are resolved. There are currently four resolver types:

  • LTS Haskell snapshots, e.g. resolver: lts-2.14
  • Stackage Nightly snapshot, e.g. resolver: nightly-2015-06-16
  • No snapshot, just use packages shipped with the compiler
    • For GHC this looks like resolver: ghc-7.10.2
    • For GHCJS this looks like resolver: ghcjs-0.1.0_ghc-7.10.2.
  • Custom snapshot

Each of these resolvers will also determine what constraints are placed on the compiler version. See the compiler-check option for some additional control over compiler version.

flags

Flags can be set for each package separately, e.g.

flags:
  package-name:
    flag-name: true

Flags will only affect packages in your packages and extra-deps settings. Packages that come from the snapshot global database are not affected.

image

The image settings are used for the creation of container images using stack image container, e.g.

image:
  containers:
    - base: "fpco/stack-build"
      add:
        static: /data/static

base is the docker image that will be used to built upon. The add lines allow you to add additional directories to your image. You can specify the name of the image using name (otherwise it defaults to the same as your project). You can also specify entrypoints. By default all your executables are placed in /usr/local/bin, but you can specify a list using executables to only add some.

When you specify entrypoints, multiple containers will be built: a project container, and one container for each entrypoint.

For example the following configuration:

image:
  containers:
  - name: myproject
    base: fpco/stack-run
    add:
      production/app-backend/conf/: /etc/app-backend
    entrypoints:
    - app-backend

will build one container tagged myproject:latest which contains the project including the /etc/app-backend configuration data.

Another container tagged myproject-app-backend:latest based on the myproject:latest will additionally contain the logic for starting the app-backend entrypoint.

user-message

A user-message is inserted by stack init when it omits packages or adds external dependencies. For example:

user-message: ! 'Warning: Some packages were found to be incompatible with the resolver
  and have been left commented out in the packages section.

  Warning: Specified resolver could not satisfy all dependencies. Some external packages
  have been added as dependencies.

  You can suppress this message by removing it from stack.yaml

'

This messages is displayed every time the config is loaded by stack and serves as a reminder for the user to review the configuration and make any changes if needed. The user can delete this message if the generated configuration is acceptable.

Non-project-specific config

Non-project config options may go in the global config (/etc/stack/config.yaml) or the user config (~/.stack/config.yaml).

docker

See Docker integration.

nix

(since 0.1.10.0)

See Nix integration.

connection-count

Integer indicating how many simultaneous downloads are allowed to happen

Default: 8

hide-th-loading

Strip out the "Loading ..." lines from GHC build output, produced when using Template Haskell

Default: true

latest-snapshot-url

URL providing a JSON with information on the latest LTS and Nightly snapshots, used for automatic project configuration.

Default: https://www.stackage.org/download/snapshots.json

local-bin-path

Target directory for stack install and stack build --copy-bins.

Default: ~/.local/bin

package-indices

package-indices:
- name: Hackage
  download-prefix: https://s3.amazonaws.com/hackage.fpcomplete.com/package/

  # at least one of the following must be present
  git: https://github.com/commercialhaskell/all-cabal-hashes.git
  http: https://s3.amazonaws.com/hackage.fpcomplete.com/00-index.tar.gz

  # optional fields, both default to false
  gpg-verify: false
  require-hashes: false

One thing you should be aware of: if you change the contents of package-version combination by setting a different package index, this can have an effect on other projects by installing into your shared snapshot database.

system-ghc

Enables or disables using the GHC available on the PATH. Useful to enable if you want to save the time, bandwidth or storage space needed to setup an isolated GHC. Default is false unless the Docker or Nix integration is enabled. In a Nix-enabled configuration, stack is incompatible with system-ghc: false.

# Turn on system GHC
system-ghc: true

install-ghc

Whether or not to automatically install GHC when necessary. Default is false, which means stack will prompt you to run stack setup as needed.

skip-ghc-check

Should we skip the check to confirm that your system GHC version (on the PATH) matches what your project expects? Default is false.

require-stack-version

Require a version of stack within the specified range (cabal-style) to be used for this project. Example: require-stack-version: "== 0.1.*"

Default: "-any"

arch/os

Set the architecture and operating system for GHC, build directories, etc. Values are those recognized by Cabal, e.g.:

arch: i386, x86_64
os: windows, linux

You likely only ever want to change the arch value. This can also be set via the command line.

extra-include-dirs/extra-lib-dirs

A list of extra paths to be searched for header files and libraries, respectively. Paths should be absolute

extra-include-dirs:
- /opt/foo/include
extra-lib-dirs:
- /opt/foo/lib

with-gcc

Specify a path to gcc explicitly, rather than relying on the normal path resolution.

with-gcc: /usr/local/bin/gcc-5

compiler-check

(Since 0.1.4)

Specifies how the compiler version in the resolver is matched against concrete versions. Valid values:

  • match-minor: make sure that the first three components match, but allow patch-level differences. For example< 7.8.4.1 and 7.8.4.2 would both match 7.8.4. This is useful to allow for custom patch levels of a compiler. This is the default
  • match-exact: the entire version number must match precisely
  • newer-minor: the third component can be increased, e.g. if your resolver is ghc-7.10.1, then 7.10.2 will also be allowed. This was the default up through stack 0.1.3

compiler

(Since 0.1.7)

Overrides the compiler version in the resolver. Note that the compiler-check flag also applies to the version numbers. This uses the same syntax as compiler resolvers like ghc-7.10.2 or ghcjs-0.1.0.20150924_ghc-7.10.2 (version used for the 'old-base' version of GHCJS). While it's useful to override the compiler for a variety of reasons, the main usecase is to use GHCJS with a stackage snapshot, like this:

resolver: lts-3.10
compiler: ghcjs-0.1.0.20150924_ghc-7.10.2
compiler-check: match-exact

ghc-options

(Since 0.1.4)

Allows specifying per-package and global GHC options:

ghc-options:
    # All packages
    "*": -Wall
    some-package: -DSOME_CPP_FLAG

Caveat emptor: setting options like this will affect your snapshot packages, which can lead to unpredictable behavior versus official Stackage snapshots. This is in contrast to the ghc-options command line flag, which will only affect the packages specified by the apply-ghc-options option.

apply-ghc-options

(Since 0.1.6)

Which packages do ghc-options on the command line get applied to? Before 0.1.6, the default value was targets

apply-ghc-options: locals # all local packages, the default
# apply-ghc-options: targets # all local packages that are targets
# apply-ghc-options: everything # applied even to snapshot and extra-deps

Note that everything is a slightly dangerous value, as it can break invariants about your snapshot database.

rebuild-ghc-options

(Since 0.1.6)

Should we rebuild a package when its GHC options change? Before 0.1.6, this was a non-configurable true. However, in most cases, the flag is used to affect optimization levels and warning behavior, for which GHC itself doesn't actually recompile the modules anyway. Therefore, the new behavior is to not recompile on an options change, but this behavior can be changed back with the following:

rebuild-ghc-options: true

ghc-variant

(Since 0.1.5)

Specify a variant binary distribution of GHC to use. Known values:

  • standard: This is the default, uses the standard GHC binary distribution
  • integersimple: Use a GHC bindist that uses integer-simple instead of GMP
  • any other value: Use a custom GHC bindist. You should specify setup-info so stack setup knows where to download it, or pass the stack setup --ghc-bindist argument on the command-line

This option is incompatible with system-ghc: true.

ghc-build

(Since 1.3.0)

Specify a specialized architecture bindist to use. Normally this is determined automatically, but you can override the autodetected value here. Possible arguments include standard, gmp4, tinfo6, and nopie.

setup-info

(Since 0.1.5)

Allows overriding from where tools like GHC and msys2 (on Windows) are downloaded. Most useful for specifying locations of custom GHC binary distributions (for use with the ghc-variant option):

setup-info:
  ghc:
    windows32-custom-foo:
      7.10.2:
        url: "https://example.com/ghc-7.10.2-i386-unknown-mingw32-foo.tar.xz"

Or without using ghc-variant:

setup-info: "https://raw.githubusercontent.com/fpco/stackage-content/master/stack/stack-setup-2.yaml"

url may be either URL or (since 1.2.0) absolute file path.

pvp-bounds

(Since 0.1.5)

When using the sdist and upload commands, this setting determines whether the cabal file's dependencies should be modified to reflect PVP lower and upper bounds. Values are none (unchanged), upper (add upper bounds), lower (add lower bounds), and both (and upper and lower bounds). The algorithm it follows is:

  • If an upper or lower bound already exists on a dependency, it's left alone
  • When adding a lower bound, we look at the current version specified by stack.yaml, and set it as the lower bound (e.g., foo >= 1.2.3)
  • When adding an upper bound, we require less than the next major version (e.g., foo < 1.3)
pvp-bounds: none

For more information, see the announcement blog post.

modify-code-page

(Since 0.1.6)

Modify the code page for UTF-8 output when running on Windows. Default behavior is to modify.

modify-code-page: false

explicit-setup-deps

(Since 0.1.6)

Decide whether a custom Setup.hs script should be run with an explicit list of dependencies, based on the dependencies of the package itself. It associates the name of a local package with a boolean. When it's true, the Setup.hs script is built with an explicit list of packages. When it's false (default), the Setup.hs script is built without access to the local DB, but can access any package in the snapshot / global DB.

Note that in the future, this will be unnecessary, once Cabal provides full support for explicit Setup.hs dependencies.

explicit-setup-deps:
    "*": true # change the default
    entropy: false # override the new default for one package

allow-newer

(Since 0.1.7)

Ignore version bounds in .cabal files. Default is false.

allow-newer: true

Note that this also ignores lower bounds. The name "allow-newer" is chosen to match the commonly used cabal option.

allow-different-user

(Since 1.0.1)

Allow users other than the owner of the stack root directory (typically ~/.stack) to use the stack installation. The default is false. POSIX systems only.

allow-different-user: true

The intention of this option is to prevent file permission problems, for example as the result of a stack command executed under sudo.

The option is automatically enabled when stack is re-spawned in a Docker process.

build

(Since 1.1.0)

Allows setting build options which are usually specified on the CLI. Here are the settings with their defaults:

build:
  library-profiling: false
  executable-profiling: false
  copy-bins: false
  prefetch: false
  keep-going: false

  # NOTE: global usage of haddock can cause build failures when documentation is
  # incorrectly formatted.  This could also affect scripts which use stack.
  haddock: false
  haddock-arguments:
    haddock-args: []      # Additional arguments passed to haddock, --haddock-arguments
    # haddock-args:
    # - "--css=/home/user/my-css"
  open-haddocks: false    # --open
  haddock-deps: false     # if unspecified, defaults to true if haddock is set
  haddock-internal: false

  # These are inadvisable to use in your global configuration, as they make the
  # stack build CLI behave quite differently.
  test: false
  test-arguments:
    rerun-tests: true   # Rerun successful tests
    additional-args: [] # --test-arguments
    # additional-args:
    # - "--fail-fast"
    coverage: false
    no-run-tests: false
  bench: false
  benchmark-opts:
    benchmark-arguments: ""
    # benchmark-arguments: "--csv bench.csv"
    no-run-benchmarks: false
  force-dirty: false
  reconfigure: false
  cabal-verbose: false
  split-objs: false

The meanings of these settings correspond directly with the CLI flags of the same name. See the build command docs and the users guide for more info.

dump-logs

(Since 1.3.0)

Control which log output from local non-dependency packages to print to the console. By default, Stack will only do this when building a single target package or if the log contains warnings, to avoid generating unnecessarily verbose output.

dump-logs: none      # don't dump logs even if they contain warnings
dump-logs: warning   # default: dump logs that contain warnings
dump-logs: all       # dump all logs for local non-dependency packages

templates

Templates used with stack new have a number of parameters that affect the generated code. These can be set for all new projects you create. The result of them can be observed in the generated LICENSE and cabal files.

The 5 parameters are: author-email, author-name, category, copyright and github-username.

  • author-email - sets the maintainer property in cabal
  • author-name - sets the author property in cabal and the name used in LICENSE
  • category - sets the category property in cabal. This is used in Hackage. For examples of categories see Packages by category. It makes sense for category to be set on a per project basis because it is uncommon for all projects a user creates to belong to the same category. The category can be set per project by passing -p "category:value" to the stack new command.
  • copyright - sets the copyright property in cabal. It is typically the name of the holder of the copyright on the package and the year(s) from which copyright is claimed. For example: Copyright: (c) 2006-2007 Joe Bloggs
  • github-username - used to generate homepage and source-repository in cabal. For instance github-username: myusername and stack new my-project new-template would result:
homepage: http://github.com/myusername/my-project#readme

source-repository head
  type: git
  location: https://github.com/myusername/my-project

These properties can be set in config.yaml as follows:

templates:
  params:
    author-name: Your Name
    author-email: youremail@example.com
    category: Your Projects Category
    copyright: 'Copyright: (c) 2016 Your Name'
    github-username: yourusername

Additionally, stack new can automatically initialize source control repositories in the directories it creates. Source control tools can be specified with the scm-init option. At the moment, only git is supported.

templates:
  scm-init: git

urls

Customize the URLs where stack looks for snapshot build plans.

The default configuration is

urls:
  latest-snapshot: https://www.stackage.org/download/snapshots.json
  lts-build-plans: https://raw.githubusercontent.com/fpco/lts-haskell/master/
  nightly-build-plans: https://raw.githubusercontent.com/fpco/stackage-nightly/master/

Note: The latest-snapshot-url field has been deprecated in favor of latest-snapshot and will be removed in a future version of stack.