config

This is a top-level module for creating configuration transitions and build setting descriptors which describe what kind of build setting (if any) a rule is.

ex: the following rule is marked as a build setting by setting the build_setting parameter of the rule() function. Specifically it is a build setting of type int and is a flag which means this build setting is callable on the command line.

  my_rule = rule(
    implementation = _impl,
    build_setting = config.int(flag = True),
    ...
  )

Members

• bool
• exec
• int
• none
• string
• string_list
• string_set
• target

bool

BuildSetting config.bool(*, flag=False)

A bool-typed build setting

Parameters

Parameter	Description
flag	bool; default is False Whether or not this build setting is callable on the command line.

exec

ExecTransitionFactory config.exec(exec_group=None)

Creates an execution transition.

Parameters

Parameter	Description
exec_group	string; or None; default is None The name of the exec group whose execution platform this transition will use. If not provided, this exec transition will use the target's default execution platform.

int

BuildSetting config.int(*, flag=False)

An integer-typed build setting

Parameters

Parameter	Description
flag	bool; default is False Whether or not this build setting is callable on the command line.

none

transition config.none()

Creates a transition which removes all configuration, unsetting all flags. Intended for the case where a dependency is data-only and contains no code that needs to be built, but should only be analyzed once.

string

BuildSetting config.string(*, flag=False, allow_multiple=False)

A string-typed build setting

Parameters

Parameter	Description
flag	bool; default is False Whether or not this build setting is callable on the command line.
allow_multiple	bool; default is False Deprecated, use a string_list setting with repeatable = True instead. If set, this flag is allowed to be set multiple times on the command line. The Value of the flag as accessed in transitions and build setting implementation function will be a list of strings. Insertion order and repeated values are both maintained. This list can be post-processed in the build setting implementation function if different behavior is desired.

string_list

BuildSetting config.string_list(*, flag=False, repeatable=False)

A string list-typed build setting. On the command line pass a list using comma-separated value like --//my/setting=foo,bar.

Parameters

Parameter	Description
flag	bool; default is False Whether or not this build setting is callable on the command line.
repeatable	bool; default is False If set, instead of expecting a comma-separated value, this flag is allowed to be set multiple times on the command line with each individual value treated as a single string to add to the list value. Insertion order and repeated values are both maintained. This list can be post-processed in the build setting implementation function if different behavior is desired.

string_set

BuildSetting config.string_set(*, flag=False, repeatable=False)

A string set-typed build setting. The value of this setting will be a set of strings in Starlark. On the command line, pass a set using a comma-separated value like --//my/setting=foo,bar.

Unlike with a string_list, the order of the elements doesn't matter and only a single instance of each element is maintained. This is recommended over string_list for flags where these properties are not needed as it can improve build performance by avoiding unnecessary configurations forking.

Parameters

Parameter	Description
flag	bool; default is False Whether or not this build setting is callable on the command line.
repeatable	bool; default is False If set, instead of expecting a comma-separated value, this flag is allowed to be set multiple times on the command line with each individual value treated as a single string to add to the set value. Only a single instance of repeated values is maintained and the insertion order does not matter.

target

transition config.target()

Creates a target transition. This is a no-op transition intended for the case where a transition object is needed, but doesn't want to actually change anything. Equivalent to cfg = "target" in attr.label().