NBPR.Buildroot.Builder (NBPR v0.4.0)

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Source-builds an NBPR package artefact tarball end-to-end.

Driven from both Mix.Tasks.Nbpr.Build (CLI) and Mix.Tasks.Nbpr.Fetch's fallback path (when no prebuilt artefact is published for the active (system, system_version, build_opts) tuple).

Pipeline:

  1. Discover deps/nerves_system_br/ and read the pinned BR version.
  2. Ensure the patched BR source tree at $NERVES_DATA_DIR/nbpr/buildroot/<version>/.
  3. Render a defconfig that layers the package + its build_opts on top of the active system's nerves_defconfig.
  4. Run BR (<pkg>-dirclean && <pkg>) against a stable per-(system, BR-version) output dir, in Docker on non-Linux hosts.
  5. Filter per-package output via BR's files-list (runtime-only).
  6. Pack into the canonical artefact tarball at output_dir/.

Returns the absolute path to the produced tarball.

Summary

Functions

build!(pkg, inputs, output_dir)

Builds the artefact for pkg against inputs.system_app/system_version, with inputs.build_opts applied. Writes the tarball into output_dir and returns its absolute path.

ensure_libc_supported!(pkg, system_source_path, system_app)

Raises when pkg declares the system's libc unsupported.

libc_of_system(system_source_path)

The C library a system's toolchain targets, read from its nerves_defconfig.

stable_output_dir(system_app, br_version)

Returns the stable per-(system, BR-version) BR output dir. Reusing across builds keeps the toolchain extraction, host-skeleton, and unchanged packages cached; make olddefconfig reconciles defconfig drift.

Functions

build!(pkg, inputs, output_dir)

@spec build!(NBPR.Package.t(), NBPR.Artifact.build_inputs(), Path.t()) :: Path.t()

Builds the artefact for pkg against inputs.system_app/system_version, with inputs.build_opts applied. Writes the tarball into output_dir and returns its absolute path.

inputs is the standard NBPR.Artifact.build_inputs/0 map (the same one used for cache-key/manifest computation in the fetch path).

ensure_libc_supported!(pkg, system_source_path, system_app)

@spec ensure_libc_supported!(NBPR.Package.t(), Path.t(), atom()) :: :ok

Raises when pkg declares the system's libc unsupported.

Refuses the combination before Buildroot spends ten minutes proving it in a compile error. The prebuild matrix already leaves these out of CI, so this guard is for a consumer whose mix firmware falls through to a source build.

libc_of_system(system_source_path)

@spec libc_of_system(Path.t()) :: NBPR.Package.libc()

The C library a system's toolchain targets, read from its nerves_defconfig.

Buildroot's own kconfig is the source of truth here rather than the toolchain's name, since that's what decides which libc the package is actually compiled against. Anything that isn't explicitly musl is treated as glibc, which is every Nerves system bar x86_64.

stable_output_dir(system_app, br_version)

@spec stable_output_dir(atom(), String.t()) :: Path.t()

Returns the stable per-(system, BR-version) BR output dir. Reusing across builds keeps the toolchain extraction, host-skeleton, and unchanged packages cached; make olddefconfig reconciles defconfig drift.