chore: enforce @svelte-vitals/core runtime-purity with eslint no-restricted-imports

[oekazuma]

Summary

@svelte-vitals/core's most important contract — "runtime-agnostic: no node: imports, no I/O, no runtime-specific globals" (stated at packages/core/src/index.ts:1-2) — was previously upheld only by documentation and review. This PR turns it into a CI gate, following the principle that prohibitions should be enforced mechanically rather than documented (see Anthropic's Claude Code steering guide).

Changes

One scoped block in eslint.config.js, applying only to packages/core/src/**/*.ts:

• no-restricted-imports: bans node:* plus common bare builtins (fs, path, os, child_process, …) with a message pointing to the Runtime interface (src/runtime.ts) as the injection point
• no-restricted-globals: bans process, __dirname, __filename, Buffer

packages/core/test/ is deliberately not covered — tests run under Node and legitimately use node: imports; purity applies to src/ only.

Verification

• Pre-check: zero existing violations in packages/core/src/ (grep for node: imports and runtime globals — 0 hits), so the rule lands green
• Positive probe: a temp file with import 'node:fs' fails eslint with the runtime-agnostic message; same for process.env via no-restricted-globals (probe removed, not committed)
• pnpm lint / pnpm typecheck / pnpm test (723 tests) — all clean; no other package's lint outcome changed
• No changeset (internal tooling only; no published package behavior change)

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Strengthened code checks in the core package to prevent use of environment-specific APIs, helping keep behavior consistent across runtimes.
  • Added clearer guidance when restricted APIs are used, encouraging safer input/output handling.

[coderabbitai]

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: d61d3372-c81e-4e80-9a61-554705e7fc87

📥 Commits

Reviewing files that changed from the base of the PR and between 4c39a57 and c38a60b.

📒 Files selected for processing (1)

• eslint.config.js

📝 Walkthrough

Walkthrough

This change adds a new ESLint configuration block targeting packages/core/src/**/*.ts, introducing no-restricted-imports to block Node built-in modules and no-restricted-globals to block runtime-specific globals, both with messages directing I/O to be injected via a Runtime interface.

Changes

ESLint core restrictions

Layer / File(s)	Summary
Restrict Node imports and globals in core package eslint.config.js	New config block for packages/core/src/**/*.ts disallows Node built-in module imports and runtime globals (process, __dirname, __filename, Buffer) with design§8 error messages instructing I/O injection via the Runtime interface.

Estimated code review effort: 1 (Trivial) | ~5 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly matches the PR’s main change: enforcing runtime-purity in @svelte-vitals/core via ESLint rules.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch advisor/009-enforce-core-purity-lint

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@eslint.config.js`:
- Around line 38-54: The import restriction in the eslint config still leaves
some Node builtin modules and subpaths unblocked, so update the allowlist in the
import pattern group to cover the missing builtins such as net, dns,
worker_threads, and path subpaths like path/posix and path/win32, or replace
this allowlist with a broader builtin-ban rule. Make the change in the config’s
patterns group so the rule consistently catches all Node builtin imports.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: a7612f35-9180-46e7-9748-4e3aeb1de45d

📥 Commits

Reviewing files that changed from the base of the PR and between 2f0bb14 and 4c39a57.

📒 Files selected for processing (1)

• eslint.config.js

[oekazuma]

Addressed in c38a60b: the hand-written bare-builtin list is replaced by a list generated from node:module's builtinModules (plus /* subpath variants), so net, dns, worker_threads, path/posix, path/win32, etc. are all covered and the list can never go stale. Verified with positive probes on path/posix, net, node:net, and path/win32 — all fail lint as intended.