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TemplatePlaceholderInfo

A provider that is used for expansions in string attribute templates

String attribute templates allow two types of user-defined placeholders, "unkeyed placeholders" like $(CXX) or $(aapt) and "keyed placeholders" that include a target key like $(cxxppflags //some:target). The expansion of each of these types is based on the TemplatePlaceholderInfo providers.

"keyed placeholders" are used for the form $(<key> <target>) or $(<key> <target> <arg>). In both cases the lookup will expect a TemplatePlaceholderInfo in the providers of <target>. It will then lookup <key> in the keyed_variables (call this the value). There are then four valid possibilities:

  1. no-arg placeholder, an arg-like value: resolve to value
  2. no-arg placeholder, a dictionary value: resolve to value["DEFAULT"]
  3. arg placeholder, a non-dictionary value: this is an error
  4. arg placeholder, a dictionary value: resolve to value[<arg>]

"unkeyed placeholders" are resolved by matching to any of the deps of the target. $(CXX) will resolve to the "CXX" value in any dep's TemplateProviderInfo.unkeyed_variables

Fields:

  • unkeyed_variables: A mapping of names to arg-like values. These are used for "unkeyed placeholder" expansion.
  • keyed_variables: A mapping of names to arg-like values or dictionary of string to arg-like values. These are used for "keyed placeholder" expansion.

TemplatePlaceholderInfo.keyed_variables​

TemplatePlaceholderInfo.keyed_variables: dict[str, typing.Any]

TemplatePlaceholderInfo.unkeyed_variables​

TemplatePlaceholderInfo.unkeyed_variables: dict[str, typing.Any]