Solving complex build.rs issues

[pnathan]

Hi,

I'm experimenting with converting my cargo project to buck and I found that I have mime-guess as a dependency about 3 levels down. Its build.rs is really quite special! https://github.com/abonander/mime_guess/blob/master/build.rs

How should I address this in the fixup?

[jsgf]

That looks like a fairly normal gen_srcs fixup with env to set MIME_TYPES_GENERATED_PATH.

[Lev1ty]

Hacked it into working for now. The issue is that the env option sets the variable for both build script and library. So had to find a way to manually resolve the path. Please let me know if there is a better alternative!

# fixup.toml

version = "=2.0.5"

[env]
# HACK: In place of $(location :mime_guess-2.0.5-build-script-run[out_dir])/mime_types_generated.rs
# The correct method causes cyclic dependency because the variable is set for both:
# :mime_guess-2.0.5 [library]
# :mime_guess-2.0.5-build-script-build [binary]
# the latter of which is a dependency of :mime_guess-2.0.5-build-script-run[out_dir].
# This only works because the OUT_DIR (set by buildscript.gen_srcs) depends on :mime_guess-2.0.5-build-script-run[out_dir].
MIME_TYPES_GENERATED_PATH = "$(location //third-party:third-party)/../../../rust/__mime_guess-2.0.5-build-script-run__/OUT_DIR/mime_types_generated.rs"

[[buildscript]]
[buildscript.gen_srcs]

# third-party BUCK

genrule(name = "third-party", cmd = "echo third-party> $OUT", out = "third-party", visibility = ["PUBLIC"])

# generated BUCK

cargo.rust_library(
    name = "mime_guess-2.0.5",
    srcs = [":mime_guess-2.0.5.crate"],
    crate = "mime_guess",
    crate_root = "mime_guess-2.0.5.crate/src/lib.rs",
    edition = "2015",
    env = {
        "MIME_TYPES_GENERATED_PATH": "$(location //third-party:third-party)/../../../rust/__mime_guess-2.0.5-build-script-run__/OUT_DIR/mime_types_generated.rs",
        "OUT_DIR": "$(location :mime_guess-2.0.5-build-script-run[out_dir])",
    },
    rustc_flags = ["@$(location :mime_guess-2.0.5-build-script-run[rustc_flags])"],
    visibility = [],
    deps = [
        ":mime-0.3.17",
        ":unicase-2.7.0",
    ],
)

cargo.rust_binary(
    name = "mime_guess-2.0.5-build-script-build",
    srcs = [":mime_guess-2.0.5.crate"],
    crate = "build_script_build",
    crate_root = "mime_guess-2.0.5.crate/build.rs",
    edition = "2015",
    env = {
        "MIME_TYPES_GENERATED_PATH": "$(location //third-party:third-party)/../../../rust/__mime_guess-2.0.5-build-script-run__/OUT_DIR/mime_types_generated.rs",
    },
    visibility = [],
    deps = [":unicase-2.7.0"],
)