Auto-commit: Sync changes [2026-03-02]

Author: Jonathan D.A. Jewell

URGENT-RESCRIPT-MIGRATION.md

@@ -0,0 +1,47 @@
+# URGENT: ReScript Migration Required
+
+**Generated:** 2026-03-02
+**Current stable ReScript:** 12.2.0
+**Pre-release:** 13.0.0-alpha.2 (2025-02-27)
+
+This repo has ReScript code that needs migration. Address in priority order.
+
+## HIGH: ReScript 11.x → 12.2.0 Upgrade Required
+
+ReScript 11 is outdated. v12 has breaking changes that need migration.
+
+- `echidna-playground (^11.1.0)`
+- `src/rescript (^11.0.1)`
+
+**Key v11 → v12 migration steps:**
+1. Update `package.json`: `"rescript": "^12.2.0"`
+2. Add `@rescript/core` and `@rescript/react` (if applicable) to dependencies
+3. Config: `bs-dependencies` → `dependencies`, `bs-dev-dependencies` → `dev-dependencies`
+4. Remove `bsc-flags` from config
+5. JSX: v3 is removed in v12 — must use JSX v4
+6. Module format: `es6`/`es6-global` → `esmodule` (now default)
+7. Migrate deprecated `Js.*` APIs → `@rescript/core` equivalents:
+   - `Js.Dict` → `Dict`, `Js.Console.log` → `Console.log`
+   - `Js.String2` → `String`, `Js.Array2` → `Array`
+   - `Js.Math` → `Math`, `Js.Float` → `Float`, `Js.Int` → `Int`
+   - `Js.Promise` → `Promise`, `Js.Nullable` → `Nullable`
+8. Functions ending in `Exn` → `OrThrow` (e.g. `getExn` → `getOrThrow`)
+9. Run `npx rescript-tools migrate` for automated codemods
+
+---
+
+## ReScript 13 Preparation (v13.0.0-alpha.2 available)
+
+v13 is in alpha. These breaking changes are CONFIRMED — prepare now:
+
+1. **`bsconfig.json` support removed** — must use `rescript.json` only
+2. **`rescript-legacy` command removed** — only modern build system
+3. **`bs-dependencies`/`bs-dev-dependencies`/`bsc-flags` config keys removed**
+4. **Uncurried `(. args) => ...` syntax removed** — use standard `(args) => ...`
+5. **`es6`/`es6-global` module format names removed** — use `esmodule`
+6. **`external-stdlib` config option removed**
+7. **`--dev`, `--create-sourcedirs`, `build -w` CLI flags removed**
+8. **`Int.fromString`/`Float.fromString` API changes** — no explicit radix arg
+9. **`js-post-build` behaviour changed** — now passes correct output paths
+
+**Migration path:** Complete all v12 migration FIRST, then test against v13-alpha.