Matt Godbolt (bot acct) 6774d762ce Construct builtin examples source explicitly at startup (#8828) ...

Follow-up to #8779 (which fixed #8601, `builtin.sourcePath` being
ignored). Two related changes:

### 1. Construct the builtin source explicitly at startup (restore
fail-fast)

#8779 made the builtin "Examples" source read its config lazily, on the
first `list()`/`load()`. That fixed correctness but moved the failure
mode: a misconfigured `sourcePath` (missing/unreadable dir) no longer
fails at startup. The server boots, passes healthchecks, takes traffic,
and then throws on the first request that opens Examples.

This restores fail-fast by constructing the source explicitly once
configuration is loaded:

- Replace the `builtin` module-level singleton with a `BuiltinSource`
class whose constructor scans the examples directory, plus a
`createBuiltinSource()` factory that reads `builtin.sourcePath`.
- `lib/sources/index.ts` exposes `createSources()` instead of a
top-level `sources` array (a top-level array would re-run config reads
at import time, reintroducing #8601).
- `initialiseApplication` constructs the sources after config load and
passes the `Source[]` to `ClientOptionsHandler` and
`setupControllersAndHandlers` (both already accept injected sources).

A bad `sourcePath` now throws during startup, before the instance
reports healthy. The lazy fix's correctness (config read after
`initialize()`) is preserved.

### 2. Single source of truth for the examples path

`GolangParser` independently re-read `('builtin', 'sourcePath',
'./examples/')` to locate `go/default.go`, duplicating where the
examples directory is defined. Export `getExamplesRoot()` from
`lib/sources/builtin.ts` and use it in both `createBuiltinSource()` and
`GolangParser`, so the config key and default live in one place.
Behaviour is unchanged (same value resolved); it removes the drift risk
if the key or default ever changes.

### Tests
Tests construct `BuiltinSource` directly with a fixture directory (no
import-order/`resetModules` dance), cover the unknown-example path,
assert fail-fast on a non-existent dir, and verify
`createBuiltinSource()` reads the configured path.

- `npx vitest --run test/sources/builtin-tests.ts
test/compilers/argument-parsers-tests.ts`
- `npm run ts-check`
- `npm run lint-check`

---------

Co-authored-by: mattgodbolt-molty <mattgodbolt-molty@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

2026-06-14 22:38:23 +01:00

..

builtin-tests.ts

Construct builtin examples source explicitly at startup (#8828)

2026-06-14 22:38:23 +01:00