Ship shared vitest/tsconfig presets — start's examples carry ~262 lines of identical config copies #2

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1. btravers commented on Sep 3, 2026

   

   btravers

   on Sep 3, 2026

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   Criterion 2 is shipped — @btravstack/tsconfig/test-d.json (#12, released in 0.4.0) and adopted across all nineteen of start's workspaces in btravstack/btravstack#258. Criterion 3 is done for that half: the copies are deleted.

   Leaving this open for criterion 1, the vitest preset, because measuring it argues against a published package and that is your call rather than mine.

   What the numbers look like now

   The issue's premise was "~262 lines of byte-identical copies" in start, and that "every btravstack monorepo with more than a couple of workspaces pays this copy tax". Measured across all four repos today, 52 vitest.config.ts files:

   repo	configs	byte-distinct
   start	24	5 of the 10 in examples/
   unthrown	15	12
   temporal-contract	5	5
   amqp-contract	8	7

   Two findings cut against a published preset:

   1. start already solved it locally, and recorded a decision about the remainder. vitest.shared.ts sits at the root and five example workspaces re-export it as a one-liner. Its own comment says why the rest are not extended:

   A workspace that needs more (coverage thresholds, globalSetup, a cache dir) writes its own config instead of extending this one — divergence should be visible in the workspace, not hidden in an override.

   2. The "common core" is not common across repos. setupFiles appears in 0 of unthrown's 15 configs — it is the library, so there is nothing to register. environment: "node" in 0 of temporal-contract's 5. include: ["src/**/*.spec.ts"] in 4 of amqp-contract's 8. A preset that three of four repos must override on its headline defaults is not a preset; it is a fourth thing to keep in sync.

   Recommendation

   Replicate the repo-local vitest.shared.ts pattern where a repo actually has near-identical configs, and do not publish @btravstack/vitest. That also avoids minting a new npm package, which has now cost two blocked releases waiting on Trusted Publisher setup (@unthrown/saga, @btravstack/tsconfig).

   If you would rather have the published preset anyway — for consistency across repos rather than for line count — say so and I will build it; the shape would be a defineConfig-mergeable base so a workspace states only its deltas, which does not conflict with the "divergence should be visible" rule since the deltas stay in the workspace file.