具体来说,它允许实现函数访问当前目标的标签、属性、配置及其依赖项的提供程序。它包含用于声明输出文件的方法以及生成输出文件的操作。
上下文对象实际上在调用实现函数期间有效。在关联函数之外访问这些对象是没用的。如需了解详情,请参阅“规则”页面。
成员
- 操作
- aspect_ids
- attr
- bin_dir
- build_file_path
- build_setting_value
- 配置
- coverage_instrumented
- created_actions
- default_provider
- disabled_features
- exec_groups
- 可执行文件
- expand_location
- expand_make_variables
- 特征
- 文件
- 文件
- fragment
- genfiles_dir
- host_configuration
- host_fragments
- info_file
- 标签
- new_file
- 输出
- resolve_command
- resolve_tools
- 规则
- runfiles
- split_attr
- target_platform_has_constraint
- 工具链
- 变量
- version_file
- workspace_name
操作
actions ctx.actions包含用于声明输出文件的方法以及生成输出文件的操作。
aspect_ids
list ctx.aspect_ids应用于目标的所有方面的 ID 列表。仅在切面实现函数中可用。
attr
struct ctx.attr用于访问特性值的结构体。值由用户提供(如果未提供,则使用默认值)。结构体的属性及其值的类型对应于提供给
rule
函数的 attrs
字典的键和值。查看使用示例。
bin_dir
root ctx.bin_dir与 bin 目录对应的根目录。
build_file_path
string ctx.build_file_path此规则的 BUILD 文件的路径(相对于源根目录)。
build_setting_value
unknown ctx.build_setting_value实验性此字段处于实验阶段,随时都可能更改。不要依赖它。
当前目标表示的 build 设置的值。对于未在规则定义中设置 build_setting
属性的规则,访问此字段会发生错误。
配置
configuration ctx.configuration默认配置。如需了解详情,请参阅配置类型。
coverage_instrumented
bool ctx.coverage_instrumented(target=None)返回是否应在针对此规则执行编译操作时生成代码覆盖率插桩;如果提供了
target
,则返回该目标指定的规则。(如果提供了非规则目标或 Starlark 规则目标,则返回 False。)检查当前规则的来源(如果未提供目标)还是目标的来源,应根据 --instrument_filter 和 --instrument_test_targets 配置设置进行插桩。这与配置中的 coverage_enabled
不同,后者记录是否针对整个运行启用覆盖率数据收集,但不指示是否应对特定目标进行插桩。
参数
参数 | 说明 |
---|---|
target
|
Target; or None ;
默认 = 无指定规则的目标。如果未提供,则默认为当前规则。 |
created_actions
StarlarkValue ctx.created_actions()对于 _skylark_testable 设置为
True
的规则,此方法会返回一个 Actions 提供程序,该提供程序表示到目前为止为当前规则创建的所有操作。对于所有其他规则,返回 None
。请注意,创建后续操作时,提供程序不会更新,因此如果要检查操作,必须再次调用此函数。这旨在帮助为规则实现辅助函数编写测试,这些函数可以接受
ctx
对象并对其创建操作。
default_provider
Provider ctx.default_provider已弃用。请改用 DefaultInfo。
disabled_features
list ctx.disabled_features用户针对此规则明确停用的功能集。
exec_groups
ExecGroupCollection ctx.exec_groups适用于此规则的执行组的集合,按名称编入索引。通过
ctx.exec_groups[name_of_group]
访问。
可执行文件
struct ctx.executable一个包含可执行文件(在标记为
executable=True
的标签类型属性中定义的)的 struct
。结构体字段与属性名称相对应。结构体中的每个值都是 File
或 None
。如果规则中未指定可选属性,则相应的结构体值为 None
。如果标签类型未标记为 executable=True
,则不会生成相应的结构体字段。查看使用示例。
expand_location
string ctx.expand_location(input, targets=[], short_paths=False)通过将
$(location //x)
替换为目标 //x 的输出文件的路径,展开给定字符串中的所有 $(location ...)
模板。扩展仅适用于指向此规则的直接依赖项的标签或可选参数 targets
中明确列出的标签。如果引用的目标有多个输出,则
$(location ...)
会导致错误。在这种情况下,请使用 $(locations ...)
,因为它会生成一个以空格分隔的输出路径列表。它也可以安全地用于单个输出文件。若要让用户在 BUILD 文件中指定命令(例如
genrule
),此函数会很有用。在其他情况下,通常最好直接操作标签。
参数
参数 | 说明 |
---|---|
input
|
必需 要展开的字符串。 |
targets
|
sequence of Targets ;
默认值 = []其他查找信息的目标列表。 |
short_paths
|
默认值 = False 使用根相对路径而不是完整的执行路径 |
None
。
expand_make_variables
string ctx.expand_make_variables(attribute_name, command, additional_substitutions)已弃用。请改用 ctx.var 访问变量。
在所有引用展开到“创建变量”后返回一个字符串。变量必须采用以下格式:
$(VAR_NAME)
。此外,$$VAR_NAME
expands to $VAR_NAME
. Examples:ctx.expand_make_variables("cmd", "$(MY_VAR)", {"MY_VAR": "Hi"}) # == "Hi" ctx.expand_make_variables("cmd", "$$PWD", {}) # == "$PWD" Additional variables may come from other places, such as configurations. Note that this function is experimental.Parameters
Parameter | Description |
---|---|
attribute_name
|
required The attribute name. Used for error reporting. |
command
|
required The expression to expand. It can contain references to "Make variables". |
additional_substitutions
|
required Additional substitutions to make beyond the default make variables. |
features
list ctx.featuresThe set of features that are explicitly enabled by the user for this rule. See example of use.
file
struct ctx.fileA
struct
containing files defined in label type attributes marked as allow_single_file
. The struct fields correspond to the attribute names. The struct value is always a File
or None
. If an optional attribute is not specified in the rule then the corresponding struct value is None
. If a label type is not marked as allow_single_file
, no corresponding struct field is generated. It is a shortcut for:list(ctx.attr.<ATTR>.files)[0]In other words, use
file
to access the (singular) default output of a dependency. See example of use.
files
struct ctx.filesA
struct
containing files defined in label or label list type attributes. The struct fields correspond to the attribute names. The struct values are list
of File
s. It is a shortcut for:[f for t in ctx.attr.<ATTR> for f in t.files]In other words, use
files
to access the default outputs of a dependency. See example of use.
fragments
fragments ctx.fragmentsAllows access to configuration fragments in target configuration.
genfiles_dir
root ctx.genfiles_dirThe root corresponding to genfiles directory.
host_configuration
configuration ctx.host_configurationThe host configuration. See the configuration type for more details.
host_fragments
fragments ctx.host_fragmentsAllows access to configuration fragments in host configuration.
info_file
File ctx.info_fileThe file that is used to hold the non-volatile workspace status for the current build request. See documentation for --workspace_status_command for more information.
label
Label ctx.labelThe label of the target currently being analyzed.
new_file
File ctx.new_file(var1, var2=unbound, var3=unbound)DEPRECATED. Use ctx.actions.declare_file.
Creates a file object. There are four possible signatures to this method:
- new_file(filename): Creates a file object with the given filename in the current package.
- new_file(file_root, filename): Creates a file object with the given filename under the given file root.
- new_file(sibling_file, filename): Creates a file object in the same directory as the given sibling file.
- new_file(file_root, sibling_file, suffix): Creates a file object with same base name of the sibling_file but with different given suffix, under the given file root.
Does not actually create a file on the file system, just declares that some action will do so. You must create an action that generates the file. If the file should be visible to other rules, declare a rule output instead when possible. Doing so enables Blaze to associate a label with the file that rules can refer to (allowing finer dependency control) instead of referencing the whole rule.
Parameters
Parameter | Description |
---|---|
var1
|
string; or root; or File ;
required |
var2
|
string; or File ;
default = unbound |
var3
|
string ;
default = unbound |
outputs
structure ctx.outputsA pseudo-struct containing all the predeclared output files, represented by
File
objects. See the Rules page for more information and examples.This field does not exist on aspect contexts, since aspects do not have predeclared outputs.
The fields of this object are defined as follows. It is an error if two outputs produce the same field name or have the same label.
- If the rule declares an
outputs
dict, then for every entry in the dict, there is a field whose name is the key and whose value is the correspondingFile
. - For every attribute of type
attr.output
that the rule declares, there is a field whose name is the attribute's name. If the target specified a label for that attribute, then the field value is the correspondingFile
; otherwise the field value isNone
. - For every attribute of type
attr.output_list
that the rule declares, there is a field whose name is the attribute's name. The field value is a list ofFile
objects corresponding to the labels given for that attribute in the target, or an empty list if the attribute was not specified in the target. - (Deprecated) If the rule is marked
executable
ortest
, there is a field named"executable"
, which is the default executable. It is recommended that instead of using this, you pass another file (either predeclared or not) to theexecutable
arg ofDefaultInfo
.
resolve_command
tuple ctx.resolve_command(command='', attribute=None, expand_locations=False, make_variables=None, tools=[], label_dict={}, execution_requirements={})(Experimental) Returns a tuple
(inputs, command, input_manifests)
of the list of resolved inputs, the argv list for the resolved command, and the runfiles metadata required to run the command, all of them suitable for passing as the same-named arguments of the ctx.action
method.Note for Windows users: this method requires Bash (MSYS2). Consider using
resolve_tools()
instead (if that fits your needs).
Parameters
Parameter | Description |
---|---|
command
|
default = '' Command to resolve. |
attribute
|
string; or None ;
default = NoneName of the associated attribute for which to issue an error, or None. |
expand_locations
|
default = False Shall we expand $(location) variables? See ctx.expand_location() for more details. |
make_variables
|
dict; or None ;
default = NoneMake variables to expand, or None. |
tools
|
sequence of Targets ;
default = []List of tools (list of targets). |
label_dict
|
default = {} Dictionary of resolved labels and the corresponding list of Files (a dict of Label : list of Files). |
execution_requirements
|
default = {} Information for scheduling the action to resolve this command. See tags for useful keys. |
resolve_tools
tuple ctx.resolve_tools(tools=[])Returns a tuple
(inputs, input_manifests)
of the depset of resolved inputs and the runfiles metadata required to run the tools, both of them suitable for passing as the same-named arguments of the ctx.actions.run
method.In contrast to
ctx.resolve_command
, this method does not require that Bash be installed on the machine, so it's suitable for rules built on Windows.
Parameters
Parameter | Description |
---|---|
tools
|
sequence of Targets ;
default = []List of tools (list of targets). |
rule
rule_attributes ctx.ruleRule attributes descriptor for the rule that the aspect is applied to. Only available in aspect implementation functions.
runfiles
runfiles ctx.runfiles(files=[], transitive_files=None, collect_data=False, collect_default=False, symlinks={}, root_symlinks={})Creates a runfiles object.
Parameters
Parameter | Description |
---|---|
files
|
sequence of Files ;
default = []The list of files to be added to the runfiles. |
transitive_files
|
depset of Files; or None ;
default = NoneThe (transitive) set of files to be added to the runfiles. The depset should use the default order (which, as the name implies, is the default).
|
collect_data
|
default = False Use of this parameter is not recommended. See runfiles guide. Whether to collect the data runfiles from the dependencies in srcs, data and deps attributes. |
collect_default
|
default = False Use of this parameter is not recommended. See runfiles guide. Whether to collect the default runfiles from the dependencies in srcs, data and deps attributes. |
symlinks
|
dict; or depset of SymlinkEntrys ;
default = {}Either a SymlinkEntry depset or the map of symlinks, prefixed by workspace name, to be added to the runfiles. See Runfiles symlinks in the rules guide. |
root_symlinks
|
dict; or depset of SymlinkEntrys ;
default = {}Either a SymlinkEntry depset or a map of symlinks to be added to the runfiles. See Runfiles symlinks in the rules guide. |
split_attr
struct ctx.split_attrA struct to access the values of attributes with split configurations. If the attribute is a label list, the value of split_attr is a dict of the keys of the split (as strings) to lists of the ConfiguredTargets in that branch of the split. If the attribute is a label, then the value of split_attr is a dict of the keys of the split (as strings) to single ConfiguredTargets. Attributes with split configurations still appear in the attr struct, but their values will be single lists with all the branches of the split merged together.
target_platform_has_constraint
bool ctx.target_platform_has_constraint(constraintValue)Returns true if the given constraint value is part of the current target platform.
Parameters
Parameter | Description |
---|---|
constraintValue
|
required The constraint value to check the target platform against. |
toolchains
ToolchainContext ctx.toolchainsToolchains for the default exec group of this rule.
var
dict ctx.varDictionary (String to String) of configuration variables.
version_file
File ctx.version_fileThe file that is used to hold the volatile workspace status for the current build request. See documentation for --workspace_status_command for more information.
workspace_name
string ctx.workspace_nameThe workspace name as defined in the WORKSPACE file.