Fixed arm32v7 builds by installing with pnpm 11

[acburdine]

refs #485

The problem

pnpm 12 is a Rust binary, and unlike every pnpm before it there is no JavaScript implementation to fall back to — the npm package is a 962KB downloader whose bin/pnpm.mjs only fetches and spawns @pnpm/exe.<platform>-<arch>. The hard gate is in its bundled get-pnpm:

if (arch !== 'x64' && arch !== 'arm64') {
    throw new Error('Sorry! pnpm currently only provides pre-built binaries for x86_64/arm64 architectures.');
}

There is no linux-arm (32-bit) target, so corepack cannot produce the version packageManager pins when building on arm32v7. That is what broke bookworm and next-bookworm.

pnpm 12.4.0 does not fix this. It added ppc64, s390x, riscv64 and musl targets, but still no 32-bit ARM — which matches what is on Docker Hub: 6.62.0 and 6.63.0 have no linux/arm/v7 entry in their manifests at all, and latest/6/bookworm still advertise the stale arm32v7 image built on 2026-08-29 (Ghost 6.61.0).

The fix

On process.arch === 'arm' only, skip corepack and install pnpm 11 instead. pnpm 11 is the last JavaScript implementation, is still released alongside 12 (latest-11, 11.26.0 shipped two days before 12.4.0), and reads the same lockfile format — both Ghost's and Ghost-CLI's lockfiles are lockfileVersion: '9.0'. Every other architecture is untouched: corepack and the hash-pinned pnpm 12, exactly as before.

Installing pnpm 11 is not sufficient on its own. It honours packageManager and self-switches straight back to pnpm 12, so it would fail identically on that arch. pnpm_config_pm_on_fail=ignore disables that (note the pnpm_config_ prefix — the npm_config_ form silently does nothing). It is exported rather than passed per invocation because Ghost-CLI spawns pnpm as a child process during ghost install, and it is inert wherever corepack is in charge, since corepack owns version switching and pnpm skips its own.

Two supporting details:

• The fallback version is pinned in versions.json via versions.sh, so the update workflow refreshes it like every other pin.
• In the -next variant the arm branch still runs corepack enable yarn. Without it the existing rm -rf /opt/yarn-* would delete the tree while /usr/local/bin/yarn still pointed at it, leaving dangling symlinks on that arch only.

Testing

Verified locally on amd64 (pnpm 11 is architecture-independent, so the lockfile behaviour transfers; the arch branch was exercised with a stubbed process.arch):

Check	Result
pnpm 11.26.0 cold install of Ghost-CLI 1.32.4's lockfile, --prod --frozen-lockfile	pass — 33 top-level packages, ghost --version runs
pnpm 11.26.0 install of the Ghost 6.63.0 release tarball's pruned lockfile	pass — including better-sqlite3 and sharp
pnpm_config_pm_on_fail propagates to a spawned child pnpm (Ghost-CLI's pattern)	pass
Arch branch selection for arm / arm64 / x64	pass — arm64 correctly does not match
Shell syntax of all four generated Dockerfiles	pass — checker validated against the base branch first

Not verified: the actual image build. This needs CI or DOI's arm32v7 builders. Still untested are the full ghost install flow under pnpm 11, and native module compilation on real armv7 (better-sqlite3 and re2 via node-gyp) — unchanged by this diff, and working before 2026-08-29, but the other thing that can fail on that arch.

Caveat

This puts arm32v7 on a different pnpm major to every other architecture. --frozen-lockfile means the installed tree should be identical, which is what makes it tolerable, but it is a real divergence and a stopgap. The durable fix is an armv7-unknown-linux-gnueabihf target upstream: pnpm already cross-compiles 13 targets with cross, and its workspace has no embedded JS engine, no jemalloc/mimalloc, and no arch-gated cfg — so nothing structural appears to block it.

Separately and not addressed here: versions.json declares s390x for bookworm, but no Ghost 6.x tag has ever published it (5-bookworm has it). Same root cause, except pnpm 12.4.0 does ship @pnpm/exe.linux-s390x — the get-pnpm guard above rejects it before reaching the branch that would resolve it, so only a direct npm install -g pnpm can reach that binary, not corepack.

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Walkthrough

The change adds pnpm 11 fallback metadata for Ghost 6 and 6-next. Dockerfile templates and generated Dockerfiles detect 32-bit ARM builds, install the fallback pnpm version, and enable Yarn through Corepack where required. Other architectures retain Corepack-managed package setup. The Dockerfiles also export pnpm_config_pm_on_fail=ignore during installation.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Suggested reviewers: ghost-slimer

Merge Risk: 🟡 Moderate · up to 2a122

ARM32 image builds now execute a registry-installed pnpm package as root without the integrity verification used by the existing Corepack path. This supply-chain exposure should be resolved or explicitly accepted before merge.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the main change: fixing arm32v7 builds by installing pnpm 11.
Description check	✅ Passed	The description directly explains the arm32v7 pnpm 12 incompatibility, the pnpm 11 fallback, configuration changes, testing, and remaining limitations.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 1…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Inline comments:
In `@Dockerfile.template`:
- Line 88: Pin the fallback pnpm artifact by a repository-controlled integrity
digest before the fallback installation. Apply the verification in
Dockerfile.template:88 and Dockerfile-next.template:100, then regenerate the
derived Dockerfiles 6-next/alpine3.23/Dockerfile:64 and
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📒 Files selected for processing (8)

• 6-next/alpine3.23/Dockerfile
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