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Ignacy Łątka acfe80ab6b chore: add ESLint with typescript-eslint (#349)
## What

Adds type-aware linting to the workspace. Until now the only static gate
on JS/TS was Prettier (formatting) and `tsc` — there was no linter, so
the whole class of bugs `tsc` doesn't catch (floating promises, misused
promises, throwing non-Errors, unsafe stringification, dead code) went
unguarded across ~450 TS files.

- **`eslint.config.mjs`** — flat config. `recommendedTypeChecked` runs
on the TS sources via an explicit `project` list (each package keeps
tests in a separate `tsconfig.test.json` that `projectService` can't
auto-discover, so it's listed explicitly). Type-checked rules are
disabled for the loosely-typed plain-JS build/dev scripts. The
`argent-private` submodule and build artifacts are ignored (mirrors
`.prettierignore`).
- **`lint` / `lint:fix`** npm scripts.
- **`.github/workflows/lint.yml`** — builds the workspace (type-aware
rules need the referenced projects' declarations) then runs `eslint .`.
Node 24 (ESLint 10 requires `^20.19 || ^22.13 || >=24`).

## Rule calibration

This is an adoption PR, so it's deliberately calibrated rather than
maximal:

- **Kept on (bug-catchers):** `no-floating-promises`,
`no-misused-promises` (with `checksVoidReturn: false` to drop the noisy
callback variant), `only-throw-error`, `no-base-to-string`,
`prefer-promise-reject-errors`, `no-unused-vars` (`_`-prefix escape
hatch), plus the ESLint recommended set.
- **Parked off as documented debt:** the high-volume style/`any`-family
rules — `no-unsafe-*`, `require-await`, `no-unnecessary-type-assertion`,
`restrict-template-expressions`, `unbound-method`, `no-explicit-any`,
etc. These flag broad classes of pre-existing code and are out of scope
here; each is commented as a ratchet target for follow-up passes.

All findings from the kept-on rules are fixed in this PR (dead
code/imports, error-cause chaining, **3 genuine floating promises**,
non-Error throws, unsafe stringification). Stale unused `eslint-disable`
directives left over in the tree were removed by `--fix`.

## Verification

Locally, all green: `eslint .` (0 errors), `tsc --build`,
`typecheck:tests`/`typecheck:scripts`, the full `vitest` suite (no
behavior change from the fixes), and `prettier --check`.

## Not included (intentionally)

Other static-analysis gates discussed (CodeQL, dependency-audit,
ShellCheck, actionlint) are out of scope for this PR.
2026-06-17 12:20:55 +02:00
..