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Phase 25. TargetTebako

FieldValue
MEPMEP-56 §Phases
StatusLANDED
Started2026-05-29 12:01 (GMT+7)
Landed2026-05-29 12:01 (GMT+7)
Tracking issue—
Tracking PR#22510
Commit89202f961a

Gate​

TestPhase25TargetTebako in transpiler3/ruby/build/phase25_test.go: builds hello_tebako.mochi (print("hi from tebako")) via Driver.Build with TargetTebako, asserts root/hello_tebako.rb, root/Gemfile, and press.sh all exist, asserts the script contains the hi from tebako literal, asserts the Gemfile contains gem "mochi-runtime", asserts press.sh contains every load-bearing fragment (#!/usr/bin/env bash, set -euo pipefail, tebako, --entry-point=hello_tebako.rb, --output=/mnt/w/hello_tebako, --root=/mnt/w/root, MOCHI_TEBAKO_IMAGE, MOCHI_TEBAKO_RUBY), asserts press.sh has the executable bit set (mode.Perm() & 0o111 != 0), and finally runs bash -n press.sh via the checkBashSyntax helper to confirm the script parses. Docker and Tebako itself are not invoked; the gate is "layout is correct and the press script is syntactically valid bash".

Build target / audit decisions​

buildTebakoPackage in transpiler3/ruby/build/build.go (lines 347 to 389) writes three artefacts: root/<name>.rb (the lowered Ruby), root/Gemfile (identical body to the bundle target: source "https://rubygems.org", ruby ">= 3.2", gem "mochi-runtime", ">= 0.1"), and press.sh (mode 0o755) at the package root. The split between root/ (the Tebako input tree) and press.sh (the host-side driver) matches Tebako's expected layout: tebako press runs against a --root directory and writes the output binary elsewhere.

The press script docker-runs ${MOCHI_TEBAKO_IMAGE:-ghcr.io/tamatebako/tebako-ubuntu-20.04:latest} with -v "$HERE":/mnt/w, invoking press --root=/mnt/w/root --entry-point=<name>.rb --output=/mnt/w/<name> --Ruby="$RUBY_VERSION" where $RUBY_VERSION defaults to 3.3.7 via ${MOCHI_TEBAKO_RUBY:-3.3.7}. Both env-var overrides exist so users on air-gapped networks can mirror the container image and pin a specific Ruby release independently of the upstream Tebako image's default. set -euo pipefail is mandatory: without -e the script silently ignores Docker failures, and without pipefail a Docker exit code can be masked by a successful tee later if a user pipes the output.

The mode 0o755 is intentional. Without the executable bit, the user has to chmod +x press.sh before running, which is friction; with it, ./press.sh works immediately. The test asserts the bit because Go file modes are notoriously easy to lose across cp and tar round-trips.

Files changed​

FilePurpose
transpiler3/ruby/build/build.gobuildTebakoPackage writes root/<name>.rb, root/Gemfile, executable press.sh (lines 347 to 389); Driver.Build dispatches TargetTebako (line 211)
transpiler3/ruby/build/phase25_test.goTestPhase25TargetTebako file existence + content + mode + bash -n assertions; checkBashSyntax helper

Test set​

  • TestPhase25TargetTebako (single test, no subtests): asserts artefact files exist, script and Gemfile contain expected literals, press.sh contains every required Docker / Tebako fragment, the executable bit is set, and bash -n press.sh parses.

Closeout notes​

Phase 25 ships with bash -n as the only "execution" of the press script; running real Tebako requires Docker plus the tamatebako image, neither of which is part of the test harness. The split was deliberate: layout + bash syntax can be validated everywhere, end-to-end binary production cannot. The two MOCHI_TEBAKO_* env vars exist so the test harness could in principle stub the image, but in practice the test skips the docker step entirely. The checkBashSyntax helper (defined at the top of the test file) was extracted because buildTruffleNative (Phase 26) and buildMRuby (Phase 27) both also emit bash -n-validated shell scripts, and centralising the lookup logic avoids three near-identical helpers.