Suggested improvements to Bazel external dependency handling (non-conflicting names, .bzl file)

[jmillikin-stripe]

This library's current definition of Bazel external dependencies makes it awkward to integrate into other projects. There are two main issues:

1. Defining deps in WORKSPACE prevents them from being imported into other workspaces with load(), so I have to copy-paste a bunch of implementation details. Other downstreams have similar issues, for example rules_docker/container/container.bzl needs full copies of same dep definitions.

2. Python import path handling gets very confused if the name of the dependency is the same as the library being imported. There are workarounds such as renaming files (as you're doing for six), but a better solution is to give the deps non-conflicting names. A Java-style domain-plus-path format is common among OSS and Google-managed libraries.

Example code:

# containerregistry/build/deps.bzl
def deps():
  native.new_http_archive(
    name = "org_pypi_python_six",
    url = "https://pypi.python.org/packages/source/s/six/six-1.9.0.tar.gz",
    sha256 = "e24052411fc4fbd1f672635537c3fc2330d9481b18c0317695b46259512c91d5",
    strip_prefix = "six-1.9.0",
    build_file_content = """py_library(
        name = "six",
        srcs = ["six.py"],
        visibility = ["//visibility:public"],
    )""",
  )
  new_git_repository(
    name = "com_github_httplib2_httplib2",
    remote = "https://github.com/httplib2/httplib2",
    commit = "1ae16e0e8e868e4b81225631ee37c6555493014b", # v0.10.3
    build_file_content = """py_library(
        name = "python2_httplib2",
        srcs = glob(["python2/httplib2/**/*.py"]),
        data = ["python2/httplib2/cacerts.txt"],
        imports = ["python2"],
        visibility = ["//visibility:public"]
    )""",
  )
  new_git_repository(
      name = "com_github_google_oauth2client",
      remote = "https://github.com/google/oauth2client",
      commit = "a731be362014d61630044c46495c5b750437ab88", # v4.0.0
      build_file_content = """py_library(
          name = "oauth2client",
          srcs = glob(["oauth2client/**/*.py"]),
          visibility = ["//visibility:public"],
          deps = [
              "@com_github_httplib2_httplib2//:python2_httplib2",
              "@org_pypi_python_six//:six",
          ]
      )""",
  )

  # ... and so on

[mattmoor]

This kind of encapsulation is really awkward in Bazel (for folks themselves writing libraries) regardless because I cannot load this symbol to call from it's repositories() method.

This is more or less the only reason I'm not using rules_python for this stuff.

[jmillikin-stripe]

That's fine. It's common to load things in WORKSPACE files. For example, I could have this in my WORKSPACE:

git_repository(name = "containerregistry", ... etc ...)

load("@containerregistry//build:deps.bzl", containerregistry_deps = "deps")

containerregistry_deps()

instead of having to copy-paste ~50 lines of dependency data.

[mattmoor]

My point is that exactly one thing can leverage this encapsulation :(

rules_docker can either use this and make consumers add the snippet above, or it can copy the ~50 lines (and get encapsulation).

I'm fine with the change, I'll see if I can find some cycles to make it.