Stack root

The Stack root is a directory where Stack stores important files.

On Unix-like operating systems and Windows, Stack can be configured to follow the XDG Base Directory Specification if the environment variable STACK_XDG is set to any non-empty value. However, Stack will ignore that configuration if the Stack root location has been set on the command line or the STACK_ROOT environment variable exists.

Location

The location of the Stack root depends on the operating system, whether Stack is configured to use the XDG Base Directory Specification, and/or whether an alternative location to Stack's default 'programs' directory has been specified.

The location of the Stack root can be configured by setting the STACK_ROOT environment variable or using Stack's --stack-root option on the command line.

Unix-likeWindowsXDG Base Directory Specification

The Stack root contains snapshot packages; (by default) tools such as GHC, in a programs directory; Stack's global YAML configuration file (config.yaml); and Stack's global-projects directory.

The default Stack root is ~/.stack.

The default Stack root is %APPDIR%\stack.

If the LOCALAPPDATA environment variable exists, the default location of tools is %LOCALAPPDATA%\Programs\stack. Otherwise, it is the programs directory in the Stack root.

Warning

If there is a space character in the %LOCALAPPDATA% path (which may be the case if the relevant user account name and its corresponding user profile path have a space) this may cause problems with building packages that make use of the GNU project's autoconf package and configure shell script files. That may be the case particularly if there is no corresponding short name ('8 dot 3' name) for the directory in the path with the space (which may be the case if '8 dot 3' names have been stripped or their creation not enabled by default). If there are problems building, it will be necessary to override the default location of Stack's 'programs' directory to specify an alternative path that does not contain space characters. Examples of packages on Hackage that make use of configure are network and process.

On Windows, the length of filepaths may be limited (to MAX_PATH), and things can break when this limit is exceeded. Setting a Stack root with a short path to its location (for example, C:\sr) can help.

The Stack root is <XDG_DATA_HOME>/stack. If the XDG_DATA_HOME environment variable does not exist, the default is ~/.local/share/stack on Unix-like operating systems and %APPDIR%\stack on Windows.

The location of config.yaml is <XDG_CONFIG_HOME>/stack. If the XDG_CONFIG_HOME environment variable does not exist, the default is ~/.config/stack on Unix-like operating systems and %APPDIR%\stack on Windows.

This approach treats:

• the project-level YAML configuration file that is common to all projects without another such file in their project directory or its ancestor directories as data rather than as part of Stack's own configuration;

• the snapshots database as essential data rather than as non-essential data that would be part of a cache, notwithstanding that Stack will rebuild that database as its contents are needed; and

• the Pantry store as essential data rather than as non-essential data that would be part of a cache, notwithstanding that Stack will download the package index and rebuild the store if it is absent.

An alternative to the default location of tools such as GHC can be specified with the local-programs-path configuration option.

The location of the Stack root is reported by command:

stack path --stack-root

The full path of Stack's global YAML configuration file is reported by command:

stack path --global-config

The location of tools such as GHC for the current platform is reported by command:

stack path --programs

Contents

The contents of the Stack root depend on the operating system, whether Stack is configured to use the XDG Base Directory Specification, and/or whether an alternative location to Stack's default 'programs' directory has been specified.

Unix-likeWindowsXDG Base Directory Specification

The Stack root contains snapshot packages; (by default) tools such as GHC, in a programs directory; Stack's global YAML configuration file (config.yaml); and Stack's global-projects directory.

The Stack root contains snapshot packages; Stack's global YAML configuration file (config.yaml); and Stack's global-projects directory. The default location of tools such as GHC and MSYS2 is outside of the Stack root.

If Stack is following the XDG Base Directory Specification, the Stack root contains what it would otherwise contain for the operating system, but Stack's global YAML configuration file (config.yaml) may be located elsewhere.

config.yaml

This is Stack's global configuration file. For further information, see the documentation for non-project specific configuration.

If the file is deleted, and Stack needs to consult it, Stack will create a file with default contents.

stack.sqlite3

This is a 'user' database that Stack uses to cache certain information. The associated lock file is stack.sqlite3.pantry-write-lock.

global-project directory

This contains:

• an explanation of the directory (README.txt);
• the project-level configuration file (stack.yaml) for the global project and its associated lock file (stack.yaml.lock); and
• if created, Stack's working directory (.stack-work) for the global project.

If the project-level configuration file is deleted, and Stack needs to consult it, Stack will recreate the contents of the directory.

pantry\hackage directory

This contains a local cache of the package index. If the contents of the directory are deleted, and Stack needs to consult the package index, Stack will seek to download the latest package index.

Info

Stack depends on package pantry which, in turn, depends on package hackage-security. The latter handles the local cache of the package index. The type CacheLayout represents the location of the files that are cached. pantry uses cabalCacheLayout :: CacheLayout, the layout that Cabal (the tool) uses. That is what specifies the names of the files used to cache the package index, including 00-index.tar and 00-index.tar.gz.

pantry directory

This contains:

• the Pantry database used by Stack (pantry.sqlite3) and its associated lock file (pantry.sqlite2.pantry-write-lock). If the database is deleted, and Stack needs to consult it, Stack will seek to create and initialise it. The database is initialised with information from the package index; and
• a database of package versions that come with each version of GHC (global-hints-cache.yaml).

programs directory

This contains a directory for the platform. That directory contains for each installed Stack-supplied tool:

• the archive file for the tool. This can be deleted;
• a file indicating the tool is installed (<tool_name>.installed); and
• a directory for the tool.

To remove a Stack-supplied tool, delete all of the above. If Stack needs a Stack-supplied tool and it is unavailable, Stack will seek to obtain it.

setup-exe-cache directory

This contains a directory for the platform. That directory contains, for each version of GHC (an associated version of Cabal (the library)) that Stack has used, an executable that Stack uses to access Cabal (the library).

If the contents of the directory are deleted, and Stack needs the executable, Stack will seek to rebuild it.

setup-exe-src directory

See the documentation for the setup-exe-cache directory. This contains the two source files (setup-<hash>.hs and setup-shim-<hash>.hs) that Stack uses to build the executable.

If the contents of the directory are deleted, and Stack needs the executable, Stack will recreate them.

The hash in the names of the source files is a hash of arguments passed to GHC when building the executable and the contents of the two source files.

The content of the setup-<hash>.hs file is the familiar:

import Distribution.Simple
main = defaultMain

The content of the setup-shim-<hash>.hs file uses main except when the executable is called with arguments repl and stack-initial-build-steps. Then Stack uses Cabal (the library) to create the autogenerated files for every configured component. Stack's stack ghci or stack repl commands call the executable with those arguments.

snapshots directory

This contains a directory for each snapshot that Stack creates when building immutable dependencies of projects.

If the contents of the directory are deleted, and the snapshot is not available to Stack when it builds, Stack will recreate the snapshot.

templates directory

This contains a .hsfile for each project template that Stack has used. For further information, see the stack templates command documentation.

If the contents of the directory are deleted, an Stack needs a project template, Stack will seek to download the template.

upload directory

This may contain saved credentials for uploading packages to Hackage (credentials.json).