gistfile1.txt

def _clickhouse_export_impl(ctx):
  print(ctx.file.server, dir(ctx.attr.server), type(ctx.attr.server))
  server_source = ctx.attr.server.files.to_list()[0]
  client_source = ctx.attr.client.files.to_list()[0]
  server_result = ctx.outputs.server
  client_result = ctx.outputs.client
  ...

_clickhouse_export = rule(
    implementation = _clickhouse_export_impl,
    attrs = {
      "server": attr.label(mandatory=True),
      "client": attr.label(mandatory=True),
      "version": attr.string(mandatory=True),
    },
    outputs = {
      "server": "%{name}-server",
      "client": "%{name}-client",
    },
)