Meaning of '@' sign in load fun

Question

I'm trying to find anything about '@' sign in load function in Bazel. We can load things like this

load("//foo/bar:file.bzl", library_alias )

But also like this

load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")

I couldn't find reason or purpuse of this. Does '@'works as '<>'in include in C/Cpp? I tried looking into Bazel/Starlark repos, but it yield no results.

Answer 1

The first argument to load() is a label to the build file you want to load from. The @ is part of the general syntax of labels. It means the label is referring to something from outside the repository in which the label appears.

//foo/bar:file.bzl means loading file.bzl from the package foo/bar in the "current" repository.

@bazel_tools//tools/build_defs/repo:http.bzl means load http.bzl from the package tools/build_defs/repo from the repository bazel_tools. (bazel_tools is a special repository that is built into bazel itself)

See:

https://bazel.build/concepts/labels

https://bazel.build/external/overview