cabal-commands.rst

Commands
========

``cabal help`` groups commands into global, package, new-style project and
legacy sections. We talk in detail about some global and package commands.

::

$ cabal help
Command line interface to the Haskell Cabal infrastructure.

See http://www.haskell.org/cabal/ for more information.

Usage: cabal [GLOBAL FLAGS] [COMMAND [FLAGS]]

Commands:
[global]
update Updates list of known packages.
install Install packages.
help Help about commands.

[package]
configure Add extra project configuration.
build Compile targets within the project.
clean Clean the package store and remove temporary files.

run Run an executable.
repl Open an interactive session for the given component.
test Run test-suites.
bench Run benchmarks.

sdist Generate a source distribution file (.tar.gz).

freeze Freeze dependencies.
haddock Build Haddock documentation.
exec Give a command access to the store.
list-bin List path to a single executable.

[new-style projects (forwards-compatible aliases)]
Since cabal-install-3.0.0.0, all 'v2-' prefixed names of commands are just aliases for the simple unprefixed names.
So v2-build is an alias for build, v2-install for install and so on.

[legacy command aliases]
No legacy commands are described.

Common Arguments and Flags
--------------------------

Arguments and flags common to some or all commands are:

.. option:: --default-user-config=file

Allows a "default" ``cabal.config`` freeze file to be passed in
manually. This file will only be used if one does not exist in the
project directory already. Typically, this can be set from the
global cabal ``config`` file so as to provide a default set of
partial constraints to be used by projects, providing a way for
users to peg themselves to stable package collections.

.. option:: --allow-newer[=pkgs], --allow-older[=pkgs]

Selectively relax upper or lower bounds in dependencies without
editing the package description respectively.

The following description focuses on upper bounds and the
:option:`--allow-newer` flag, but applies analogously to
:option:`--allow-older` and lower bounds. :option:`--allow-newer`
and :option:`--allow-older` can be used at the same time.

If you want to install a package A that depends on B >= 1.0 && <
2.0, but you have the version 2.0 of B installed, you can compile A
against B 2.0 by using ``cabal install --allow-newer=B A``. This
works for the whole package index: if A also depends on C that in
turn depends on B < 2.0, C's dependency on B will be also relaxed.

Example:

::

$ cd foo
$ cabal configure
Resolving dependencies...
cabal: Could not resolve dependencies:
[...]
$ cabal configure --allow-newer
Resolving dependencies...
Configuring foo...

Additional examples:

::

# Relax upper bounds in all dependencies.
$ cabal install --allow-newer foo

# Relax upper bounds only in dependencies on bar, baz and quux.
$ cabal install --allow-newer=bar,baz,quux foo

# Relax the upper bound on bar and force bar==2.1.
$ cabal install --allow-newer=bar --constraint="bar==2.1" foo

It's also possible to limit the scope of :option:`--allow-newer` to single
packages with the ``--allow-newer=scope:dep`` syntax. This means
that the dependency on ``dep`` will be relaxed only for the package
``scope``.

Example:

::

# Relax upper bound in foo's dependency on base; also relax upper bound in
# every package's dependency on lens.
$ cabal install --allow-newer=foo:base,lens

# Relax upper bounds in foo's dependency on base and bar's dependency
# on time; also relax the upper bound in the dependency on lens specified by
# any package.
$ cabal install --allow-newer=foo:base,lens --allow-newer=bar:time

Finally, one can enable :option:`--allow-newer` permanently by setting
``allow-newer: True`` in the ``~/.cabal/config`` file. Enabling
'allow-newer' selectively is also supported in the config file
(``allow-newer: foo, bar, baz:base``).

.. option:: --preference=preference

Specify a soft constraint on versions of a package. The solver will
attempt to satisfy these preferences on a "best-effort" basis.

.. option:: --enable-build-info

Generate accurate build information for build components.

Information contains meta information, such as component type, compiler type, and
Cabal library version used during the build, but also fine grained information,
such as dependencies, what modules are part of the component, etc...

On build, a file ``build-info.json`` (in the ``json`` format) will be written to
the root of the build directory.

.. note::
The format and fields of the generated build information is currently
experimental. In the future we might add or remove fields, depending
on the needs of other tooling.

.. code-block:: json

{
"cabal-lib-version": "",
"compiler": {
"flavour": "",
"compiler-id": "",
"path": ""
},
"components": [
{
"type": "",
"name": "",
"unit-id": "",
"compiler-args": [
""
],
"modules": [
""
],
"src-files": [
""
],
"hs-src-dirs": [
""
],
"src-dir": "",
"cabal-file": ""
}
]
}

.. jsonschema:: ./json-schemas/build-info.schema.json

.. option:: --disable-build-info

(default) Do not generate detailed build information for built components.

Already generated `build-info.json` files will be removed since they would be stale otherwise.

cabal list-bin
--------------

``cabal list-bin`` will either (a) display the path for a single executable or (b)
complain that the target doesn't resolve to a single binary. In the latter case,
it will name the binary products contained in the package. These products can
be used to narrow the search and get an actual path to a particular executable.

Example showing a failure to resolve to a single executable.

::

$ cabal list-bin cabal-install
cabal: The list-bin command is for finding a single binary at once. The
target 'cabal-install' refers to the package cabal-install-#.#.#.# which
includes the executable 'cabal', the test suite 'unit-tests', the test suite
'mem-use-tests', the test suite 'long-tests' and the test suite
'integration-tests2'.

For a scope that results in only one item we'll get a path.

::

$ cabal list-bin cabal-install:exes
/.../dist-newstyle/build/.../cabal/cabal

$ cabal list-bin cabal-install:cabal
/.../dist-newstyle/build/.../cabal/cabal

We can also scope to test suite targets as they produce binaries.

::

$ cabal list-bin cabal-install:tests
cabal: The list-bin command is for finding a single binary at once. The
target 'cabal-install:tests' refers to the test suites in the package
cabal-install-#.#.#.# which includes the test suite 'unit-tests', the test
suite 'mem-use-tests', the test suite 'long-tests' and the test suite
'integration-tests2'.

$ cabal list-bin cabal-install:unit-tests
/.../dist-newstyle/.../unit-tests/unit-tests

Note that ``cabal list-bin`` will print the executables' location, but
will not make sure that these executables actually exist (i.e., have
been successfully built). In order to determine the correct location,
it may invoke the configuration step (see ``cabal configure``).

cabal configure
---------------

``cabal configure`` takes a set of arguments and writes a
``cabal.project.local`` file based on the flags passed to this command.
``cabal configure FLAGS; cabal build`` is roughly equivalent to
``cabal build FLAGS``, except that with ``configure`` the flags
are persisted to all subsequent calls to ``build``.

``cabal configure`` is intended to be a convenient way to write out
a ``cabal.project.local`` for simple configurations; e.g.,
``cabal configure -w ghc-7.8`` would ensure that all subsequent
builds with ``cabal build`` are performed with the compiler
``ghc-7.8``. For more complex configuration, we recommend writing the
``cabal.project.local`` file directly (or placing it in
``cabal.project``!)

``cabal configure`` inherits options from ``Cabal``. semantics:

- Any flag accepted by ``./Setup configure``.

- Any flag accepted by ``cabal configure`` beyond
``./Setup configure``, namely ``--cabal-lib-version``,
``--constraint``, ``--preference`` and ``--solver.``

- Any flag accepted by ``cabal install`` beyond ``./Setup configure``.

- Any flag accepted by ``./Setup haddock``.

The options of all of these flags apply only to *local* packages in a
project; this behavior is different than that of ``cabal install``,
which applies flags to every package that would be built. The motivation
for this is to avoid an innocuous addition to the flags of a package
resulting in a rebuild of every package in the store (which might need
to happen if a flag actually applied to every transitive dependency). To
apply options to an external package, use a ``package`` stanza in a
``cabal.project`` file.

There are two ways of modifying the ``cabal.project.local`` file through
``cabal configure``, either by appending new configurations to it, or
by simply overwriting it all. Overwriting is the default behaviour, as
such, there's a flag ``--enable-append`` to append the new configurations
instead. Since overwriting is rather destructive in nature, a backup system
is in place, which moves the old configuration to a ``cabal.project.local~``
file, this feature can also be disabled by using the ``--disable-backup``
flag.

cabal update
------------

``cabal update`` updates the state of the package index. If the
project contains multiple remote package repositories it will update
the index of all of them (e.g. when using overlays).

Some examples:

::

$ cabal update # update all remote repos
$ cabal update head.hackage # update only head.hackage

Target Forms
------------

A cabal command target can take any of the following forms:

- A package target: ``package``, which specifies that all enabled
components of a package to be built. By default, test suites and
benchmarks are *not* enabled, unless they are explicitly requested
(e.g., via ``--enable-tests``.)

- A component target: ``[package:][ctype:]component``, which specifies
a specific component (e.g., a library, executable, test suite or
benchmark) to be built.

- All packages: ``all``, which specifies all packages within the project.

- Components of a particular type: ``package:ctypes``, ``all:ctypes``:
which specifies all components of the given type. Where valid
``ctypes`` are:

- ``libs``, ``libraries``,
- ``flibs``, ``foreign-libraries``,
- ``exes``, ``executables``,
- ``tests``,
- ``benches``, ``benchmarks``.

- A module target: ``[package:][ctype:]module``, which specifies that the
component of which the given module is a part of will be built.

- A filepath target: ``[package:][ctype:]filepath``, which specifies that the
component of which the given filepath is a part of will be built.

- A script target: ``path/to/script``, which specifies the path to a script
file. This is supported by ``build``, ``repl``, ``run``, and ``clean``.
Script targets are not part of a package.

cabal build
-----------

``cabal build`` takes a set of targets and builds them. It
automatically handles building and installing any dependencies of these
targets.

In component targets, ``package:`` and ``ctype:`` (valid component types
are ``lib``, ``flib``, ``exe``, ``test`` and ``bench``) can be used to
disambiguate when multiple packages define the same component, or the
same component name is used in a package (e.g., a package ``foo``
defines both an executable and library named ``foo``). We always prefer
interpreting a target as a package name rather than as a component name.

Some example targets:

::

$ cabal build lib:foo-pkg # build the library named foo-pkg
$ cabal build foo-pkg:foo-tests # build foo-tests in foo-pkg
$ cabal build src/Lib.s # build the library component to
# which "src/Lib.hs" belongs
$ cabal build app/Main.hs # build the executable component of
# "app/Main.hs"
$ cabal build Lib # build the library component to
# which the module "Lib" belongs
$ cabal build path/to/script # build the script as an executable

Beyond a list of targets, ``cabal build`` accepts all the flags that
``cabal configure`` takes. Most of these flags are only taken into
consideration when building local packages; however, some flags may
cause extra store packages to be built (for example,
``--enable-profiling`` will automatically make sure profiling libraries
for all transitive dependencies are built and installed.)

When building a script, the executable is cached under the cabal directory.
See ``cabal run`` for more information on scripts.

In addition ``cabal build`` accepts these flags:

.. option:: --only-configure

When given we will forego performing a full build and abort after running
the configure phase of each target package.

cabal repl
----------

``cabal repl TARGET`` loads all of the modules of the target into
GHCi as interpreted bytecode. In addition to ``cabal build``'s flags,
it additionally takes the ``--repl-options`` and ``--repl-no-load`` flags.

To avoid ``ghci`` specific flags from triggering unneeded global rebuilds these
flags are now stripped from the internal configuration. As a result
``--ghc-options`` will no longer (reliably) work to pass flags to ``ghci`` (or
other repls). Instead, you should use the new ``--repl-options`` flag to
specify these options to the invoked repl. (This flag also works on ``cabal
repl`` and ``Setup repl`` on sufficiently new versions of Cabal.)

The ``repl-no-load`` flag disables the loading of target modules at startup.

Currently, it is not supported to pass multiple targets to ``repl``
(``repl`` will just successively open a separate GHCi session for
each target.)

It also provides a way to experiment with libraries without needing to download
them manually or to install them globally.

This command opens a REPL with the current default target loaded, and a version
of the ``vector`` package matching that specification exposed.

::

$ cabal repl --build-depends "vector >= 0.12 && < 0.13"

Both of these commands do the same thing as the above, but only exposes ``base``,
``vector``, and the ``vector`` package's transitive dependencies even if the user
is in a project context.

::

$ cabal repl --ignore-project --build-depends "vector >= 0.12 && < 0.13"
$ cabal repl --project='' --build-depends "vector >= 0.12 && < 0.13"

This command would add ``vector``, but not (for example) ``primitive``, because
it only includes the packages specified on the command line (and ``base``, which
cannot be excluded for technical reasons).

::

$ cabal repl --build-depends vector --no-transitive-deps

``repl`` can open scripts by passing the path to the script as the target.

::

$ cabal repl path/to/script

The configuration information for the script is cached under the cabal directory
and can be pre-built with ``cabal build path/to/script``.
See ``cabal run`` for more information on scripts.

cabal run
---------

``cabal run [TARGET [ARGS]]`` runs the executable specified by the
target, which can be a component, a package or can be left blank, as
long as it can uniquely identify an executable within the project.
Tests and benchmarks are also treated as executables.

See `the build section <#cabal-build>`__ for the target syntax.

When ``TARGET`` is one of the following:

- A component target: execute the specified executable, benchmark or test suite.

- A package target:
1. If the package has exactly one executable component, it will be selected.
2. If the package has multiple executable components, an error is raised.
3. If the package has exactly one test or benchmark component, it will be selected.
4. Otherwise an issue is raised.

- The path to a script: execute the script at the path.

- Empty target: Same as package target, implicitly using the package from the current
working directory.

Except in the case of the empty target, the strings after it will be
passed to the executable as arguments.

If one of the arguments starts with ``-`` it will be interpreted as
a cabal flag, so if you need to pass flags to the executable you
have to separate them with ``--``.

::

$ cabal run target -- -a -bcd --argument

``run`` supports running script files that use a certain format.
Scripts look like:

::

#!/usr/bin/env cabal
{- cabal:
build-depends: base ^>= 4.14
, shelly ^>= 1.10
-}
{- project:
with-compiler: ghc-8.10.7
-}

main :: IO ()
main = do
...

Where there cabal metadata block is mandatory and contains fields from a
package executable block, and the project metadata block is optional and
contains fields that would be in the cabal.project file in a regular project.

Only some fields are supported in the metadata blocks, and these fields are
currently not validated. See
`#8024 `__ for details.

A script can either be executed directly using `cabal` as an interpreter or
with the command:

::

$ cabal run path/to/script

The executable is cached under the cabal directory, and can be pre-built with
``cabal build path/to/script`` and the cache can be removed with
``cabal clean path/to/script``.

A note on targets: Whenever a command takes a script target and it matches the
name of another target, the other target is preferred. To load the script
instead pass it as an explicit path: ./script

By default, scripts are run at silent verbosity (``--verbose=0``). To show the
build output for a script either use the command

::

$ cabal run --verbose=n path/to/script

or the interpreter line

::

#!/usr/bin/env -S cabal run --verbose=n

For more information see :cfg-field:`verbose`

cabal freeze
------------

``cabal freeze`` writes out a **freeze file** which records all of
the versions and flags that are picked by the solver under the
current index and flags. Default name of this file is
``cabal.project.freeze`` but in combination with a
``--project-file=my.project`` flag (see :ref:`project-file
`)
the name will be ``my.project.freeze``.
A freeze file has the same syntax as ``cabal.project`` and looks
something like this:

.. highlight:: cabal

::

constraints: HTTP ==4000.3.3,
HTTP +warp-tests -warn-as-error -network23 +network-uri -mtl1 -conduit10,
QuickCheck ==2.9.1,
QuickCheck +templatehaskell,
-- etc...

For end-user executables, it is recommended that you distribute the
``cabal.project.freeze`` file in your source repository so that all
users see a consistent set of dependencies. For libraries, this is not
recommended: users often need to build against different versions of
libraries than what you developed against.

cabal bench
-----------

``cabal bench [TARGETS] [OPTIONS]`` runs the specified benchmarks
(all the benchmarks in the current package by default), first ensuring
they are up to date.

cabal test
----------

``cabal test [TARGETS] [OPTIONS]`` runs the specified test suites
(all the test suites in the current package by default), first ensuring
they are up to date.

cabal haddock
-------------

``cabal haddock [FLAGS] [TARGET]`` builds Haddock documentation for
the specified packages within the project.

If a target is not a library :cfg-field:`haddock-benchmarks`,
:cfg-field:`haddock-executables`, :cfg-field:`haddock-internal`,
:cfg-field:`haddock-tests` will be implied as necessary.

cabal exec
----------

``cabal exec [FLAGS] [--] COMMAND [--] [ARGS]`` runs the specified command
using the project's environment. That is, passing the right flags to compiler
invocations and bringing the project's executables into scope.

cabal install
-------------

``cabal install [FLAGS] [TARGETS]`` builds the specified target packages and
symlinks/copies their executables in ``installdir`` (usually ``~/.cabal/bin``).

.. warning::

If not every package has an executable to install, use ``all:exes`` rather
than ``all`` as the target. To overwrite an installation, use
``--overwrite-policy=always`` as the default policy is ``never``.

For example this command will build the latest ``cabal-install`` and symlink
its ``cabal`` executable:

::

$ cabal install cabal-install

In addition, it's possible to use ``cabal install`` to install components
of a local project. For example, with an up-to-date Git clone of the Cabal
repository, this command will build cabal-install HEAD and symlink the
``cabal`` executable:

::

$ cabal install exe:cabal

Where symlinking is not possible (eg. on some Windows versions) the ``copy``
method is used by default. You can specify the install method
by using ``--install-method`` flag:

::

$ cabal install exe:cabal --install-method=copy --installdir=$HOME/bin

Note that copied executables are not self-contained, since they might use
data-files from the store.

.. _adding-libraries:

Adding libraries to GHC package environments
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

It is also possible to "install" libraries using the ``--lib`` flag. For
example, this command will build the latest Cabal library and install it:

::

$ cabal install --lib Cabal

This works by managing GHC package environment files. By default, it is writing
to the global environment in ``~/.ghc/$ARCH-$OS-$GHCVER/environments/default``.
``install`` provides the ``--package-env`` flag to control which of these
environments is modified.

This command will modify the environment file in the current directory:

::

$ cabal install --lib Cabal --package-env .

This command will modify the environment file in the ``~/foo`` directory:

::

$ cabal install --lib Cabal --package-env foo/

Do note that the results of the previous two commands will be overwritten by
the use of other style commands, so it is not recommended to use them inside
a project directory.

This command will modify the environment in the ``local.env`` file in the
current directory:

::

$ cabal install --lib Cabal --package-env local.env

This command will modify the ``myenv`` named global environment:

::

$ cabal install --lib Cabal --package-env myenv

If you wish to create a named environment file in the current directory where
the name does not contain an extension, you must reference it as ``./myenv``.

You can learn more about how to use these environments in `this section of the
GHC manual `_.

cabal clean
-----------

``cabal clean [FLAGS]`` cleans up the temporary files and build artifacts
stored in the ``dist-newstyle`` folder.

By default, it removes the entire folder, but it can also spare the configuration
and caches if the ``--save-config`` option is given, in which case it only removes
the build artefacts (``.hi``, ``.o`` along with any other temporary files generated
by the compiler, along with the build output).

``cabal clean [FLAGS] path/to/script`` cleans up the temporary files and build
artifacts for the script, which are stored under the .cabal/script-builds directory.

In addition when clean is invoked it will remove all script build artifacts for
which the corresponding script no longer exists.

cabal sdist
-----------

``cabal sdist [FLAGS] [TARGETS]`` takes the crucial files needed to build ``TARGETS``
and puts them into an archive format ready for upload to Hackage. These archives are stable
and two archives of the same format built from the same source will hash to the same value.

``cabal sdist`` takes the following flags:

.. option:: -l, --list-only

Rather than creating an archive, lists files that would be included.

Output is to ``stdout`` by default. The file paths are relative to the project's root
directory.

.. option:: -o, --output-directory

Sets the output dir, if a non-default one is desired. The default is
``dist-newstyle/sdist/``. ``--output-directory -`` will send output to ``stdout``
unless multiple archives are being created.

.. option:: --null-sep

Only used with ``--list-only``. Separates filenames with a NUL
byte instead of newlines.

``sdist`` is inherently incompatible with sdist hooks (which were removed in `Cabal-3.0`),
not due to implementation but due to fundamental core invariants
(same source code should result in the same tarball, byte for byte)
that must be satisfied for it to function correctly in the larger build ecosystem.
``autogen-modules`` is able to replace uses of the hooks to add generated modules, along with
the custom publishing of Haddock documentation to Hackage.

cabal gen-bounds
----------------

``cabal gen-bounds [FLAGS]`` generates bounds for all dependencies that do not
currently have them. Generated bounds are printed to stdout. You can then
paste them into your .cabal file.

See `the section on generating dependency version bounds `__ for more details and examples.

cabal outdated
--------------

``cabal outdated [FLAGS]`` checks for outdated dependencies in the package
description file or freeze file.

``cabal outdated`` supports the following flags:

.. option:: --v1-freeze-file

Read dependency version bounds from the freeze file.

(``cabal.config``) instead of the package description file
(``$PACKAGENAME.cabal``).

.. option:: --v2-freeze-file

:since: 2.4

Read dependency version bounds from the v2-style freeze file
(by default, ``cabal.project.freeze``) instead of the package
description file. ``--new-freeze-file`` is an alias for this flag
that can be used with pre-2.4 ``cabal``.

.. option:: --project-file PROJECTFILE

:since: 2.4

Read dependendency version bounds from the v2-style freeze file
related to the named project file (i.e., ``$PROJECTFILE.freeze``)
instead of the package desctription file. If multiple ``--project-file``
flags are provided, only the final one is considered. This flag
must only be passed in when ``--new-freeze-file`` is present.

.. option:: --simple-output

Print only the names of outdated dependencies, one per line.

.. option:: --exit-code

Exit with a non-zero exit code when there are outdated dependencies.

.. option:: -q, --quiet

Don't print any output. Implies ``-v0`` and ``--exit-code``.

.. option:: --ignore PACKAGENAMES

Don't warn about outdated dependency version bounds for the packages in this list.

.. option:: --minor [PACKAGENAMES]

Ignore major version bumps for these packages.

E.g. if there's a version 2.0 of a package ``pkg`` on Hackage and the freeze
file specifies the constraint ``pkg == 1.9``, ``cabal outdated --freeze
--minor=pkg`` will only consider the ``pkg`` outdated when there's a version
of ``pkg`` on Hackage satisfying ``pkg > 1.9 && < 2.0``. ``--minor`` can also
be used without arguments, in that case major version bumps are ignored for
all packages.

See `the section on listing outdated dependency version bounds `__ for more details and examples.