The `stack build` command and its synonyms¶

stack build [TARGET] [--dry-run] [--pedantic] [--fast] [--ghc-options OPTIONS]
            [--flag PACKAGE:[-]FLAG] [--dependencies-only | --only-snapshot |
              --only-dependencies | --only-locals] [--file-watch |
              --file-watch-poll] [--watch-all] [--exec COMMAND [ARGUMENT(S)]]
            [--only-configure] [--trace] [--profile] [--no-strip]
            [--[no-]library-profiling] [--[no-]executable-profiling]
            [--[no-]library-stripping] [--[no-]executable-stripping]
            [--[no-]haddock] [--haddock-arguments HADDOCK_ARGS]
            [--[no-]open] [--[no-]haddock-deps] [--[no-]haddock-internal]
            [--[no-]haddock-hyperlink-source] [--[no-]copy-bins]
            [--[no-]copy-compiler-tool] [--[no-]prefetch] [--[no-]keep-going]
            [--[no-]keep-tmp-files] [--[no-]force-dirty] [--[no-]test]
            [--[no-]rerun-tests] [--ta|--test-arguments TEST_ARGS] [--coverage]
            [--no-run-tests] [--test-suite-timeout ARG]
            [--[no-]tests-allow-stdin] [--[no-]bench]
            [--ba|--benchmark-arguments BENCH_ARGS] [--no-run-benchmarks]
            [--[no-]reconfigure] [--cabal-verbosity VERBOSITY |
              --[no-]cabal-verbose] [--[no-]split-objs] [--skip ARG]
            [--[no-]interleaved-output] [--ddump-dir ARG]

stack build and its synonyms (stack test, stack bench, stack haddock and stack install) are Stack's primany command. The command provides a simple interface for simple tasks and flexibility for more complicated goals.

See the introductory part of Stack's user's guide for an introduction to the command.

Synonyms¶

The synonym commands for stack build are:

Synonym command	Equivalent `stack build` command flag
`stack test`	`stack build --test`
`stack bench`	`stack build --bench`
`stack haddock`	`stack build --haddock`
`stack install`	`stack build --copy-bins`

The advantage of the synonym commands is that they are convenient and short. The advantage of the flags is that they compose. See the examples below.

Components¶

Every Cabal package is made up of one or more components. It can have an optional public library component, one or more optional executable components, one or more optional test suite components, and one or more optional benchmark components.

Stack allows you to identify a specific component to be built. For example, stack build mypackage:test:mytests will build (and run - see further below) the mytests component of the mypackage package. mytests must be a test suite component.

By default, if a test suite component is targeted, the component is built and run. The running behaviour can be disabled with the --no-run-tests flag. Similarly, if a benchmark component is targeted, it is built and run unless the running behaviour is disabled with the --no-run-benchmarks flag.

This ability to specify a component applies only to a local package. With dependencies, Stack will always build the library (if present) and all executables (if any), and ignore test suites and benchmarks. If you want more control over a package, you must add it to your packages setting in your project-level configuration file (stack.yaml).

Target syntax¶

stack build takes a list of one or more optional targets to be built. The supported syntaxes for targets are:

package, e.g. stack build foobar, is the most commonly used target. It will try to find the package in the following locations: local packages, extra deps, snapshots, and package index (e.g. Hackage). If it's found in the package index, then the latest version of that package from the index is implicitly added to your extra dependencies.

If the package is a local package, the library and executable components are selected to be built. If the --test and --bench flags are set, then all of the test suite and benchmark components, respectively, are selected to be built.

If package is a GHC boot package (packages that come with GHC and are included in GHC's global package database), the behaviour can be complex. If the boot package has not been 'replaced', then stack build will, effectively, do nothing. However, if the boot package has been 'replaced' then stack build will specify the latest version of that package in the package index, which may differ from the version provided by the version of GHC specified by the snapshot. A boot package will be treated as 'replaced' if the package is included directly in the Stackage snapshot or it depends on a package included directly in the snapshot. Stackage snapshots do not include directly most boot packages but some snapshots may include directly some boot packages. In particular, some snapshots include directly Win32 (which is a boot package on Windows) while others do not. For example, if Cabal (a boot package) is not a local package or an extra dep, then stack build Cabal with Stackage snapshot LTS Haskell 20.25 will:
- on Windows, try to build the latest version of Cabal in the package index (because that snapshot includes Win32 directly, and Cabal depends on Win32 and so is treated as 'replaced'); and
- on non-Windows, effectively, do nothing (because Cabal is not 'replaced').
package identifier, e.g. stack build foobar-1.2.3, is usually used to include specific package versions from the package index.

If the package name conflicts with that of a local package, then Stack fails with an error.

Otherwise, this is the same as using stack build foobar (that is, ignoring the specified version), unless the specified version exists in the package index. If it exists, then the latest revision of that version from the package index is used.
component. Instead of referring to an entire package and letting Stack decide which components to build, you select individual components from inside a package. This can be done for more fine-grained control over which test suites to run, or to have a faster compilation cycle. There are multiple ways to refer to a specific component (provided for convenience):
- <package-name>:lib or <package-name>:<comp-type>:<comp-name> (where the component type, <comp-type>, is one of exe, test, or bench) is the most explicit. The library component type (lib) does not have an associated component name, <comp-name>.
  
  Note
  
  When any exe component is specified, all of the package's executable components will be built. This is due to limitations in all currently released versions of Cabal. See issue#1046
- <package-name>:<comp-name> allows you to leave out the component type, as that will often be unique for a given component name. For example, stack build mypackage:mytestsuite.
- :<comp-name> is a useful shortcut, saying "find the component <comp-name> in all of the local packages". This will result in an error if more than one package has a component with the specified name. To continue the above example, stack build :mytestsuite.
directory, e.g. stack build foo/bar, will find all local packages that exist in the given directory hierarchy and then follow the same procedure as passing in package names as mentioned above. There's an important caveat here: if your directory name is parsed as one of the above target types, it will be treated as that. Explicitly starting your target with ./ can be a good way to avoid that, e.g. stack build ./foo.

Note

stack build . will target local packages in the current working directory or its subdirectories.

stack build with no targets specified will build all local packages.

Command stack ide targets to get a list of the available targets in your project.

Controlling what gets built¶

Stack will automatically build the necessary dependencies. See the introductory part of Stack's user's guide for information about how these dependencies get specified.

In addition to specifying targets, you can also control what gets built, or retained, with the following flags:

`--bench` flag¶

Pass the flag to add benchmark components to the targets, if specific components are not identified. The stack bench synonym sets this flag.

`--dependencies-only` flag¶

Pass the flag to skip building the targets. The flag --only-dependencies has the same effect.

`--[no-]dry-run` flag¶

Default: Disabled

Set the flag to build nothing and output information about the build plan.

`--flag` option¶

stack build --flag <package_name>:[-]<flag_name> sets (or unsets) the specified Cabal flag for the specified package.

This option can be specified multiple times to set (or unset) multiple Cabal flags.

The same Cabal flag name can be set (or unset) for multiple packages (at the command line only) with:

stack build --flag *:[-]<flag_name>

Note

Currently you needs to list all of your modules that interpret flags in the other-modules section of a Cabal file. Cabal (the tool) has a different behavior currently and doesn't require that the modules be listed. This may change in a future release.

`--[no-]force-dirty` flag¶

Default: Disabled

Set the flag to force rebuild of packages even when it doesn't seem necessary based on file dirtiness.

`--[no-]haddock` flag¶

Default: Disabled

Set the flag to build Haddock documentation. This may cause a lot of packages to get re-built, so that the documentation links work. The stack haddock synonym sets this flag.

`--haddock-arguments` option¶

stack haddock --haddock-arguments <haddock_arguments> passes the specified arguments to the Haddock tool.

`--[no-]haddock-deps` flag¶

Default: Enabled (if building Haddock documnentation)

Unset the flag to disable building Haddock documentation for dependencies.

`--[no-]haddock-hyperlink-source` flag¶

Default: Enabled

Unset the flag to disable building building hyperlinked source for Haddock.

`--[no-]haddock-internal` flag¶

Default: Disabled

Set the flag to enable building Haddock documentation for internal modules.

`--[no-]keep-going` flag¶

Default (stack build): Disabled

Default (stack test or stack bench): Enabled

Set the flag to continue building packages even after some build step fails. The packages which depend upon the failed build won't get built.

`--[no-]keep-tmp-files` flag¶

Default: Disabled

Set the flag to keep intermediate files and build directories that would otherwise be considered temporary and deleted. It may be useful to inspect these, if a build fails. By default, they are not kept.

`--only-configure` flag¶

0.1.4.0

Pass the flag to perform only the configure step, not any builds. This is intended for tool usage. It may break when used on multiple packages at once.

Note

If there are downstream actions that require a package to be built then a full build will occur, even if the flag is passed.

`--only-dependencies` flag¶

Pass the flag to skip building the targets. The flag --dependencies-only has the same effect.

`--only-locals` flag¶

Pass the flag to build only packages in the local database. Fails if the build plan includes packages in the snapshot database.

`--only-snapshot` flag¶

Pass the flag to build only snapshot dependencies, which are cached and shared with other projects.

`--[no-]reconfigure` flag¶

Default: Disabled

Set the flag to force reconfiguration even when it doesn't seem necessary based on file dirtiness. This is sometimes useful with custom Setup.hs files, in particular when they depend on external data files.

`--skip` option¶

stack build --skip <component> skips building the specified components of a local package. It allows you to skip test suites and benchmark without specifying other components (e.g. stack test --skip long-test-suite will run the tests without the long-test-suite test suite). Be aware that skipping executables won't work the first time the package is built due to an issue in Cabal.

This option can be specified multiple times to skip multiple components.

`--test` flag¶

Pass the flag to add test suite components to the targets, if specific components are not identified. The stack test synonym sets this flag.

Controlling when building occurs¶

`--file-watch` flag¶

Pass the flag to rebuild your project every time a file changes. By default it will take into account all files belonging to the targets you specify. See also the --watch-all flag.

`--file-watch-poll` flag¶

Like the --file-watch flag, but based on polling the file system instead of using events to determine if a file has changed.

`--watch-all` flag¶

2.5.1

Pass the flag to rebuild your project every time any local file changes (from project packages or from local dependencies). See also the --file-watch flag.

Controlling what happens after building¶

`--exec` option¶

stack build --exec "<command> [<arguments>]" will run the specified command after a successful build.

Flags affecting GHC's behaviour¶

`--[no-]executable-profiling` flag¶

Default: Disabled

Set the flag to enable executable profiling for TARGETs and all its dependencies.

`--[no-]executable-stripping` flag¶

Default: Enabled

Unset the flag to disable executable stripping for TARGETs and all its dependencies.

`--fast` flag¶

Pass the flag to build your project with the GHC option -O0. -O0 disables GHC's optimisations (which is GHC's default).

`--ghc-options` option¶

stack build --ghc-options <ghc_options> passes the specified command line options to GHC, depending on Stack's apply-ghc-options YAML configuration option. This option can be specified multiple times.

GHC's command line options are order-dependent and evaluated from left to right. Later options can override earlier options. Stack applies the options specified at the command line last. Any existing GHC command line options of a package are applied after those specified at the command line.

`--[no-]library-profiling` flag¶

Default: Disabled

Set the flag to enable library profiling for TARGETs and all its dependencies.

`--[no-]library-stripping` flag¶

Default: Enabled

Unset the flag to disable library stripping for TARGETs and all its dependencies.

`--pedantic` flag¶

Pass the flag to build your project with the GHC options -Wall and -Werror. -Wall turns on all warning options that indicate potentially suspicious code. -Werror makes any warning into a fatal error.

`--profile` flag¶

Pass the flag to enable profiling in libraries, executables, etc. for all expressions, and generate a profiling report in tests or benchmarks.

`--[no-]split-objs` flag¶

Experimental

Default: Disabled

Set the flag to enable the GHC option --split-objs. This will reduce output size (at the cost of build time).

Note

The behaviour of this feature may be changed and improved. You will need to clean your project's Stack working directory before use. If you want to compile all dependencies with split-objs, you will need to delete the snapshot (and all snapshots that could reference that snapshot).

`--no-strip` flag¶

Pass the flag to disable DWARF debugging symbol stripping in libraries, executables, etc. for all expressions, producing larger executables but allowing the use of standard debuggers/profiling tools/other utilities that use debugging symbols.

`--trace` flag¶

Pass the flag to enable profiling in libraries, executables, etc. for all expressions, and generate a backtrace on exception.

Flags affecting other tools' behaviour¶

`--PROG-option` options¶

2.11.1

PROG is a program recognised by Cabal (the library) and one of alex, ar, c2hs, cpphs, gcc, greencard, happy, hsc2hs, hscolour, ld, pkg-config, strip and tar.

stack build --PROG-option <PROG_argument> passes the specified command line argument to PROG, if it used by Cabal during the configuration step. This option can be specified multiple times. For example, if the program happy is used by Cabal during the configuration step, you could command stack build --happy-option=--ghc or stack build --happy-option --ghc to pass to happy its --ghc flag.

By default, all and any --PROG-option options on Stack's command line are applied to all local packages (targets or otherwise). This behaviour can be changed. See the apply-prog-options configuration option.

Stack can also be configured to pass Cabal's --PROG-option, --PROG-options or other options to Cabal during the configuration step. For further information, see the documentation for the configure-options configuration option.

Flags relating to build outputs¶

`--[no]-cabal-verbose` flag¶

Default: Disabled

Set the flag to enable verbose output from Cabal (the library). This flag is an alternative to the --cabal-verbosity option.

`--[no]-cabal-verbosity` option¶

stack build --cabal-verbosity <verbosity_level> sets the specified verbosity level for output from Cabal (the library). It accepts Cabal's numerical and extended syntax. This option is an alternative to setting the --cabal-verbose flag.

`--[no-]copy-bins` flag¶

0.1.3.0

Default: Disabled

Set the flag to enable copying of built executable files (binaries) of targets to Stack's local binary directory (see stack path --local-bin). The stack install synonym sets this flag.

`--[no-]copy-compiler-tool` flag¶

1.6.1

Default: Disabled

Set the flag to enable copying of built executable files (binaries) of targets to Stack's compiler tools binary directory (see stack path --compiler-tools-bin).

`--coverage` flag¶

Pass the flag to generate a code coverage report. For further information, see the code coverage documentation.

`--ddump-dir` option¶

GHC has a number of ddump-* flags and options to allow dumping out of intermediate structures produced by the compiler. They include the -ddump-to-file flag that causes the output from other flags to be dumped to a file or files.

stack build --ddump_dir <relative_directory> causes Stack to copy *.dump-* files to subdirectories of the specified directory, which is relative to Stack's working directory for the project.

For example:

stack build --ghc-options "-ddump-to-file -ddump-timings" --ddump-dir my-ddump-dir

`--[no-]interleaved-output` flag¶

2.1.1

Default: Enabled

Set the flag for interleaved output. With interleaved output, each line of output from each package being built (targets and dependencies) is sent to the console as it happens and output relating to different packages can be interleaved. Each line will be prefixed with the name of the relevant package. The spacing between the prefix and the output will be set based on the longest relevant package name, so that the start of the output itself aligns. For example (extract):

hpack            > build
mustache         > configure
hpack            > Preprocessing library for hpack-0.35.0..
hpack            > Building library for hpack-0.35.0..
mustache         > Configuring mustache-2.4.1...
hpack            > [ 1 of 29] Compiling Data.Aeson.Config.Key
hpack            > [ 2 of 29] Compiling Data.Aeson.Config.KeyMap
mustache         > build
hpack            > [ 3 of 29] Compiling Data.Aeson.Config.Util
mustache         > Preprocessing library for mustache-2.4.1..
mustache         > Building library for mustache-2.4.1..
hpack            > [ 4 of 29] Compiling Hpack.Haskell
hpack            > [ 5 of 29] Compiling Hpack.Utf8
mustache         > [1 of 8] Compiling Paths_mustache
hpack            > [ 6 of 29] Compiling Imports
hpack            > [ 7 of 29] Compiling Hpack.Util
mustache         > [2 of 8] Compiling Text.Mustache.Internal

Unset the flag for non-interleaved output. With non-interleaved output, the build output from GHC (as opposed to from Stack) in respect of dependencies is ignored. The behaviour then depends whether there is one target package or more than one. There can be one target if the project has a single package or if one package is targetted in a multi-package project (for example, using stack build <package_name>).

One target package: The build output for the target package is sent to the standard error output stream of the console as it happens.
More than one target package: The build output from GHC (as opposed to from Stack) for each target package is sent to a log file for that package, unless an error occurs that prevents that. If color in output is in use, there will be two files, one with extension .log without color codes and one with extension .log-color with color codes. At the end of the build, the location of the directory containing the log files is reported. To also output the contents of the log files to the standard error output stream of the console at the end of the build, use Stack's dump-logs option. For further information about that option, see the YAML configuration documentation. The default dump-logs mode is to output the contents of any log files that include GHC warnings.

`--[no]-open` flag¶

Default: Disabled

Set the flag to enable opening the local Haddock documentation in the browser.

Other flags and options¶

`--[no]-prefetch` flag¶

Default: Disabled

Set the flag to enable fetching packages necessary for the build immediately. This can be useful with stack build --dry-run.

`--tests-allow-stdin` flag¶

2.9.3

Default: Enabled

Cabal defines a test suite interface 'exitcode-stdio-1.0' where the test suite takes the form of an executable and the executable takes nothing on the standard input channel (stdin). Pass this flag to override that specification and allow the executable to receive input on that channel. If you pass --no-tests-allow-stdin and the executable seeks input on the standard input channel, an exception will be thown.

Examples¶

All the following examples assume that:

if stack build is commanded outside of a project directory, there is no stack.yaml file in the current directory or ancestor directory and, consequently, the project-level configuration will be determined by a stack.yaml file in the global-project directory in the Stack root (for further information, see the YAML configuration documentation); and
if stack build is commanded in a project directory, there is a stack.yaml file in that directory.

Examples:

In the project directory, stack build --test --copy-bins or, equivalently, stack test --copy-bins or stack install --test, will build libraries, executables, and test suites, run the test suites, and then copy the executables to Stack's local binary directory (see stack path --local-bin). This is an example of the flags composing.
The following example uses a clone of the wai repository. The wai project comprises a number of packages, including wai-extra and warp. In the wai project directory, the command:
```
stack build --file-watch --test --copy-bins --haddock wai-extra :warp warp:doctest --exec 'echo Yay, it worked!'
```
will start Stack up in file watch mode, waiting for files in your project to change. When first starting, and each time a file changes, it will do all of the following.
- Build the wai-extra package and its test suites
- Build the warp executable
- Build the warp package's doctest component (which is a test site)
- Run all of the wai-extra package's test suite components and the doctest test suite component
- If all of that succeeds:
  - Copy generated executables to Stack's local binary directory (see stack path --local-bin)
  - Run the command echo Yay, it worked!
The following example uses the Adga package and assumes that Adga-2.6.3 is the latest version in the package index (e.g. Hackage) and is not a version in the snapshot specified by the stack.yaml in the global-project directory in the Stack root.

Outside a project directory, stack build Adga-2.6.3 --copy-bins or, equivalently, stack install Agda-2.6.3, will attempt to build the libraries and executables of the identified version of the package in the package index (using the stack.yaml file in the global-project directory in the Stack root), and then copy the executables to Stack's local binary directory (see stack path --local-bin).

If a different snapshot is required to build the identified version of the package, then that can be specified at the command line. For example, to use the most recent Stackage Nightly snapshot:
```
stack --resolver nightly install Agda-2.6.3
```
Alternatively, Stack can be used to unpack the package from the package index into a local project directory named after the package identifier (for further infomation, see the stack unpack command documentation) and, if the package does not provide its own Stack configuration file (stack.yaml), to attempt to initialise that configuration (for further information, see the stack init command documentation). For example:
```
stack unpack Agda-2.6.3
cd Agda-2.6.3  # Change to the project directory
stack init     # Attempt to create a project stack.yaml file
stack install  # Equivalent to stack build --copy-bins
```

The stack build command and its synonyms¶

Synonyms¶

Components¶

Target syntax¶

Controlling what gets built¶

--bench flag¶

--dependencies-only flag¶

--[no-]dry-run flag¶

--flag option¶

--[no-]force-dirty flag¶

--[no-]haddock flag¶

--haddock-arguments option¶

--[no-]haddock-deps flag¶

--[no-]haddock-hyperlink-source flag¶

--[no-]haddock-internal flag¶

--[no-]keep-going flag¶

--[no-]keep-tmp-files flag¶

--only-configure flag¶

--only-dependencies flag¶

--only-locals flag¶

--only-snapshot flag¶

--[no-]reconfigure flag¶

--skip option¶

--test flag¶

Controlling when building occurs¶

--file-watch flag¶

--file-watch-poll flag¶

--watch-all flag¶

Controlling what happens after building¶

--exec option¶

Flags affecting GHC's behaviour¶

--[no-]executable-profiling flag¶

--[no-]executable-stripping flag¶

--fast flag¶

--ghc-options option¶

--[no-]library-profiling flag¶

--[no-]library-stripping flag¶

--pedantic flag¶

--profile flag¶

--[no-]split-objs flag¶

--no-strip flag¶

--trace flag¶

Flags affecting other tools' behaviour¶

--PROG-option options¶

Flags relating to build outputs¶

--[no]-cabal-verbose flag¶

--[no]-cabal-verbosity option¶

--[no-]copy-bins flag¶

--[no-]copy-compiler-tool flag¶

--coverage flag¶

--ddump-dir option¶

--[no-]interleaved-output flag¶

--[no]-open flag¶

Other flags and options¶

--[no]-prefetch flag¶

--tests-allow-stdin flag¶

Examples¶

The `stack build` command and its synonyms¶

`--bench` flag¶

`--dependencies-only` flag¶

`--[no-]dry-run` flag¶

`--flag` option¶

`--[no-]force-dirty` flag¶

`--[no-]haddock` flag¶

`--haddock-arguments` option¶

`--[no-]haddock-deps` flag¶

`--[no-]haddock-hyperlink-source` flag¶

`--[no-]haddock-internal` flag¶

`--[no-]keep-going` flag¶

`--[no-]keep-tmp-files` flag¶

`--only-configure` flag¶

`--only-dependencies` flag¶

`--only-locals` flag¶

`--only-snapshot` flag¶

`--[no-]reconfigure` flag¶

`--skip` option¶

`--test` flag¶

`--file-watch` flag¶

`--file-watch-poll` flag¶

`--watch-all` flag¶

`--exec` option¶

`--[no-]executable-profiling` flag¶

`--[no-]executable-stripping` flag¶

`--fast` flag¶

`--ghc-options` option¶

`--[no-]library-profiling` flag¶

`--[no-]library-stripping` flag¶

`--pedantic` flag¶

`--profile` flag¶

`--[no-]split-objs` flag¶

`--no-strip` flag¶

`--trace` flag¶

`--PROG-option` options¶

`--[no]-cabal-verbose` flag¶

`--[no]-cabal-verbosity` option¶

`--[no-]copy-bins` flag¶

`--[no-]copy-compiler-tool` flag¶

`--coverage` flag¶

`--ddump-dir` option¶

`--[no-]interleaved-output` flag¶

`--[no]-open` flag¶

`--[no]-prefetch` flag¶

`--tests-allow-stdin` flag¶