How to generate config file in an external bazel dependency

Question

I'm new to bazel and trying to automatize updates in the MapIt database and code.

I named the root folder for my bazel project bazel_mapit where there is the WORKSPACE file and the BUILD file for this external dependency as follows.

WORSPACE:

new_git_repository(
    name            = "mapit_repo",
    remote          = "https://github.com/mysociety/mapit",
    tag             = "v2.0",
    build_file      = "mapit_repo.BUILD",
    init_submodules = 1,

)

mapit_reop.BUILD:

package(default_visibility = ["//visibility:public"])

filegroup(
    name = "mapit_files",
    srcs = glob(
        [
            "**/*",
        ],
        exclude = [
            "**/LICENSE",
            "**/*.zip",
        ],
    ),
)

Now I want to generate the configuration file conf/general.yml inside the MapIt sources. The problem now is, when I add the following code to the mapit_repo.BUILD file, I getting errors that bazel can't find

'@bazel_mapit//:general_yml.bzl'

mapit_repo.BUILD (extension):

load("@bazel_mapit//:general_yml.bzl", "general_yml")

general_yml(
    name = 'generate_general_yml',
    bzl_mapit_db_user = 'foo',
)

filegroup (
    name = 'mapit_general_yml',
    srcs = ['conf/general.yml'],
    data = ['conf/general.yml-example'],
)

How can I generate a config file in an external dependency?

Update:

This is the content of the working mapit_repo.BUILD file:

package(default_visibility = ["//visibility:public"])

filegroup(
    name = "mapit_files",
    srcs = glob(
        [
            "**/*",
        ],
        exclude = [
            "**/LICENSE",
            "**/*.zip",
        ],
    ),
)

load("@//conf:general_yml.bzl", "general_yml")

general_yml(
  name = 'generate_general_yml',
  bzl_mapit_db_user = 'foo',
)

filegroup (
  name = 'mapit_general_yml',
  srcs = ['conf/general.yml'],
  data = ['@//conf:general.yml.tmpl'],
)

Answer 1

I think all that needs to change is the load() mapit_repo.BUILD. That build file is going to be evaluated from within the external workspace, so to reference the bzl file in the main workspace, you can use @//:general_yml.bzl . (That is, the empty workspace name refers to the main workspace)