How to add non-bazel project as a build target for current bazel project?

Question

Background: I have a C++ header-only library eg : mpack mpack uses cmake build system. However, I want to use some of its functions in my project (my_project) which uses bazel build system.

I was following the steps from https://docs.bazel.build/versions/1.2.0/external.html#non-bazel-projects

Goal: Trying to include mpack.hpp in sni_filter.cc

My changes:

a) Added the following snippet in WORKSPACE file

new_local_repository(
    name = "mpack-c",
    path = "mpack-c",
    build_file = "BUILD.mpack-c",
)

b) Added BUILD.mpack-c

cc_library(
    name = "mpack-lib",
    srcs = glob(["**"]),
    visibility = ["//visibility:public"],
)

c) Added the mpack-lib target in BUILD file of sni_filter

envoy_cc_library(
    name = "sni_filter_lib",
    srcs = ["sni_filter.cc"],
    hdrs = ["sni_filter.h"],    
    deps = [       
        "@mpack-c//:mpack-lib",
    ],
)

When I am trying to run a bazel build, its throwing an error :

ERROR: Error fetching repository: /xoxo/xyz/abc/repo/src/engine/WORKSPACE:28:21: In new_local_repository rule //external:mpack-c the 'build_file' attribute does not specify an existing file (/xoxo/xyz/abc/repo/src/engine/BUILD.mpack-c does not exist)
ERROR: /xoxo/xyz/abc/repo/src/engine/my_proj/sni_filter/BUILD:11:17: //my_proj/sni_filter:sni_filter_lib depends on @mpack-c//:mpack-lib in repository @mpack-c which failed to fetch. no such package '@mpack-c//': In new_local_repository rule //external:mpack-c the 'build_file' attribute does not specify an existing file (/xoxo/xyz/abc/repo/src/engine/BUILD.mpack-c does not exist)

Attached the directory struct

Answer 1

The path in the new_local_repository attribute needs to either be absolute or relative to the directory the WORKSPACE file is located in. Also, the label in the build_file attribute needs to specified relative to the workspace root.

So, in your WORKSPACE file replace:

new_local_repository(
    name = "mpack-c",
    path = "mpack-c",
    build_file = "BUILD.mpack-c",
)

with:

new_local_repository(
    name = "mpack-c",
    path = "mpack",
    build_file = "mpack/BUILD.mpack-c",
)

For reference, see the documentation.