nxplpc: framework-arduino-lpc8xx pin is hardcoded — platform_packages override in platformio.ini is silently ignored (blocks FastLED#3325 bisection)

[zackees]

TL;DR

ArduinoCoreLpc8xx (and by symmetry any other framework package whose source we may need to override per-build) pins its URL + commit SHA + sha256 as const &str in the Rust source. There is no platform_packages lookup. The orchestrator already has env_config in scope but throws away any consumer-provided framework override.

This breaks LPC8xx bisection on the fbuild backend — currently blocking FastLED/FastLED#3325 (LPC845-BRK JSON-RPC echo regression bisection, root issue FastLED/FastLED#3300). PlatformIO honors platform_packages = framework-arduino-lpc8xx@<URL>#<sha> and re-clones per pin; fbuild silently ignores the same line.

Repro / evidence

crates/fbuild-packages/src/library/arduino_core_lpc8xx.rs (HEAD e165ea4f, v2.2.31):

const ACLPC_COMMIT: &str   = "195a2eddd31eba8472ceaffa6a1a1902f72439ae";
const ACLPC_VERSION: &str  = "0.1.0+g195a2ed";
const ACLPC_URL: &str      = "https://github.com/zackees/ArduinoCore-LPC8xx/archive/195a2eddd31eba8472ceaffa6a1a1902f72439ae.tar.gz";
const ACLPC_CHECKSUM: &str = "366de74b93179ba4b5e8ac9e527f15f189d9e26bcedd030fe11c11a2c907f3e4";

impl ArduinoCoreLpc8xx {
    pub fn new(project_dir: &Path) -> Self { /* uses the 4 consts unconditionally */ }
}

Both call sites pass only project_dir, never an override:

crates/fbuild-build/src/nxplpc/orchestrator.rs:121:
    let core = fbuild_packages::library::ArduinoCoreLpc8xx::new(&params.project_dir);
crates/fbuild-build/src/nxplpc/mod.rs:39:
    let core = fbuild_packages::library::ArduinoCoreLpc8xx::new(project_dir);

Meanwhile the orchestrator already parses platformio.ini and has env_config in scope (orchestrator.rs:78–89). The platform_packages key is just not read.

By contrast PlatformIO's nxplpc-arduino platform.json:

"framework-arduino-lpc8xx": {
    "type": "framework",
    "optional": true,
    "version": "https://github.com/zackees/ArduinoCore-LPC8xx.git"
}

— bare URL, no SHA. Whatever's on the consumer's platformio.ini platform_packages line wins.

Impact: this blocks downstream bisection workflows

FastLED/FastLED#3325 needs to bisect 7+ ArduinoCore-LPC8xx commits (4560e6c41d..da8f2b8b42) to find a JSON-RPC bring-up regression. On the PIO backend the bisect step is one platformio.ini edit + one bash compile lpc845brk --platformio (~60s). On the fbuild backend the equivalent step requires:

1. Edit arduino_core_lpc8xx.rs to swap ACLPC_COMMIT / ACLPC_VERSION / ACLPC_URL.
2. Download the new tarball, compute sha256, update ACLPC_CHECKSUM.
3. Rebuild fbuild from source (cargo build --release, ~minutes).
4. Re-run bash compile lpc845brk (~60s).
5. Test the device.

That makes the fbuild backend effectively unbisectable. And because fbuild's currently-pinned commit 195a2eddd3 is one of the top regression suspects in #3325 (ArduinoCore-LPC8xx #29, the pre-CRP linker pack), the asymmetry is actively biting right now.

The cache structure already supports per-pin caches (.fbuild/prod/cache/platforms/zackees-ArduinoCore-LPC8xx/<url-hash>/<version>+g<short-sha>/). Only the input wiring is missing.

Proposed fix

1. Plumb a URL+SHA override through ArduinoCoreLpc8xx

Add an opt-in constructor that takes the override:

impl ArduinoCoreLpc8xx {
    pub fn new(project_dir: &Path) -> Self { /* keep default consts */ }

    /// Consumer-overridden core source. URL must be a downloadable
    /// `archive/<sha>.tar.gz` (or `.zip`) — i.e. resolvable to a single
    /// commit. Checksum is None because the consumer is responsible for
    /// trusting the pin.
    pub fn with_override(project_dir: &Path, url: &str, version: &str) -> Self { /* … */ }
}

version is needed because the cache subdir is <version>+g<short-sha>/ and otherwise the override would collide with the default-pinned cache.

2. Read platform_packages in the nxplpc orchestrator

In orchestrator.rs after env_config is resolved, look up the framework override:

let core_override = env_config
    .get("platform_packages")
    .and_then(parse_platform_packages_entry("framework-arduino-lpc8xx"));

let core = match core_override {
    Some((url, sha)) => ArduinoCoreLpc8xx::with_override(
        &params.project_dir, &url, &format!("0.1.0+g{}", &sha[..7])),
    None => ArduinoCoreLpc8xx::new(&params.project_dir),
};

A small parse_platform_packages_entry helper that handles the PIO syntax — name@<URL>#<sha> and name@<owner/repo>#<sha> — would also let the same plumbing serve any future ARM/Arduino framework package we vendor (e.g. nrf52, samd, sam if/when they land).

3. Checksum behavior with override

Two reasonable choices, prefer (a):

(a) Skip the sha256 check when an override is set and log a warning. The consumer is explicitly overriding for development / bisection; demanding they recompute sha256 per step defeats the point.

(b) Auto-compute sha256 on first fetch and cache it locally (per cache-subdir manifest). Slightly more work but stays content-addressed.

4. Surface the override in fbuild's build log

One INFO line at the start of compile so it's obvious from terminal scrollback when a non-default core is in use:

ArduinoCore-LPC8xx OVERRIDE: https://github.com/zackees/ArduinoCore-LPC8xx/archive/<sha>.tar.gz (default pinned: 195a2eddd3)

Out of scope (but worth noting)

• Same gap likely exists for any other framework-* package whose source is const-pinned in fbuild-packages. A grep for const .*_URL: &str across crates/fbuild-packages/src/library/ will enumerate them; consider whether to generalize the override plumbing into PackageBase so adding override-support to a new package is one constructor variant rather than a new code path.
• This issue is not requesting that fbuild start consuming PlatformIO's framework defaults. The platform.json indirection is a separate (larger) discussion. This is just: when the consumer's platformio.ini explicitly says "use this commit," respect it.

Acceptance criteria

• platform_packages = framework-arduino-lpc8xx@<URL>#<sha> in [env:lpc845brk] causes fbuild to fetch and use the consumer-specified commit.
• Default behavior (no override) is unchanged — same pin, same checksum, same cache subdir.
• Cache subdir for an override is distinct from default (no collision).
• An INFO log line in bash compile lpc845brk makes the override visible at runtime.
• Per-step bisection (edit platformio.ini, re-compile, test) completes in seconds, not minutes.

Refs

• [BLOCKER] LPC845-BRK AutoResearch bring-up echo returns empty RX (suspected HardFault) — blocks #3102 FastLED#3300 — LPC845-BRK bring-up echo regression (root).
• [#3300 bisect] Find the commit that broke LPC845-BRK JSON-RPC echo — bisect Arduino-core LPC8xx FastLED#3325 — the bisection plan currently blocked on the fbuild side.
• zackees/ArduinoCore-LPC8xx — the upstream whose commits we need to walk.