Add has_parallel_download feature to detect if rctx.download supports parallel downloads (#29) Coming in 7.1.0, [repository_ctx#download](https://bazel.build/rules/lib/builtins/repository_ctx#download) has a new argument, block: > If set to false, the call returns immediately and instead of the regular return value, it returns a token with one single method, wait(), which blocks until the download is finished and returns the usual return value or throws as usual. It would be useful to be able to update repository rules to use this feature when available.
Use this to determine the availability of a Bazel feature in your ruleset. It works under the hood by comparing the Bazel version against a known range in which the feature is available. Example usage:
load("@bazel_features//:features.bzl", "bazel_features") if bazel_features.toolchains.has_optional_toolchains: # Do something
The features.bzl file contains the list of features.
References to global Starlark symbols that do not exist cause load time errors, which means that their availability in Bazel cannot be tested via a regular feature. Instead, use bazel_features.globals.<symbol>, which is <symbol> if the symbol is available and None else.
See globals.bzl for the list of symbols that can be checked for in this way.