[mroderick]

Summary

Deploys to Heroku have been rejected since PR #3051 (json 2.21.2 → 3.1.0): rake assets:precompile aborts with ArgumentError: unknown keyword: create_additions. This PR bumps execjs to 2.10.2, which fixes it, and adds a CI job that runs the asset precompile so this class of breakage fails in CI instead of at deploy time.

Key changes

• execjs 2.10.1 → 2.10.2 (Gemfile.lock only). 2.10.1 passed create_additions: false to JSON.parse, a keyword json 3.x removed; 2.10.2 (released 2026-08-12) calls JSON.parse(output) without it. Terser's constraint (>= 0.3.0, < 3) already allows the new version, so no Gemfile change is needed.
• New Assets Precompile job in .github/workflows/ruby.yml: rake assets:precompile under RAILS_ENV=production. The task boots the app without connecting to a database, so a placeholder DATABASE_URL resolves the adapter, and PLANNER_SECRET (the app's own secret, set in config/initializers/secret_token.rb) plus AWS credentials (AWS_ACCESS_KEY, AWS_SECRET_ACCESS_KEY, read by config/initializers/carrier_wave.rb) stand in for the real values; nothing connects to S3 during precompile.

Detail

The failure path: rake assets:precompile → Sprockets → Terser 1.2.8 → ExecJS 2.10.1 ExecJS::ExternalRuntime::Context#extract_result, which called ::JSON.parse(output, create_additions: false) (external_runtime.rb:69). json 3.1.0 removed the create_additions keyword from JSON.parse (flagged as a TODO in json 2.21.2: "extract :create_additions support to another gem for version 3.0"), so every production build died while minifying the first JS asset. The build log confirmed the bundler cache swap of json 2.21.2 for 3.1.0 in the same run.

Why CI missed it: the workflow runs RuboCop, parallel RSpec (uncompressed assets, RAILS_ENV=test), and bundler-audit — nothing loads ExecJS or Terser. The only caller of ExecJS is the Terser compressor wired in config/environments/production.rb.

Verified locally with json 3.1.0 installed: ExecJS.compile("1+1") raises the ArgumentError under execjs 2.10.1 and succeeds under 2.10.2; RAILS_ENV=production PLANNER_SECRET=fake DATABASE_URL=postgres://u:p@localhost:5432/planner_placeholder bundle exec rake assets:precompile completes.

Review notes

No special focus requested; the diff is lockfile plus one CI job. Deliberately not done: no Node version pinning (the Heroku warning about the default Node.js version is pre-existing), and no removal of the bin/bundle binstub (also pre-existing, unrelated).