Port NPM To Perry

Port an npm package to Perry

Status: experimental. This skill is a first pass at systematizing what Perry contributors have been doing ad-hoc. Results will vary by package. If it produces bad patches or misses known gaps, please comment on issue #115 — we want to iterate on this.

Your job is to make an npm package compile natively under Perry. Perry compiles a subset of TypeScript to native code via LLVM, so not everything runs. The mechanical side — "pull the package into the compile" — is handled by perry.compilePackages in package.json. The hard part is identifying + patching the constructs Perry doesn't support.

Inputs

• $ARGUMENTS: the package to port. Either a package specifier (@scope/name, name) or a path to a package directory.

Steps

1. Locate the package

If $ARGUMENTS is a specifier, resolve it to node_modules/<name> in the current project (or ask the user to run npm install <name> first if it's not present). If it's a path, use it directly.

Read package.json at the package root. Note:

• main / module / exports — the entry points
• dependencies — transitive deps that will also need to port
• gypfile: true or a binding.gyp file — stop: this package has a native C/C++ addon and cannot be compiled natively. Report this to the user and suggest an alternative package (Perry is AOT-only and has no runtime JS/V8 fallback).
• prebuilds/ directory or .node files anywhere — same as above, native addon.

2. Scan for known gaps

Perry's TypeScript subset is documented at docs/src/language/limitations.md. Run these searches against the package's source:

# Dynamic code
grep -rn "\beval(" <pkg>/
grep -rn "new Function(" <pkg>/
grep -rn "require(" <pkg>/ | grep -v "^.*://"   # dynamic require
grep -rn "await import(" <pkg>/

# Supported, but with caveats — surface for review, not blockers
grep -rn "new Proxy(" <pkg>/    # limited trapping: docs/src/language/limitations.md#limited-proxy-trapping
grep -rn "new WeakMap(" <pkg>/  # targets retained, never collected: docs/src/language/limitations.md#weak-references-retain-their-targets
grep -rn "new WeakRef(" <pkg>/  # same retention caveat

# Reflection / metadata
grep -rn "Reflect\." <pkg>/

# Decorators
grep -rn "^@[A-Z]" <pkg>/ --include="*.ts"

# Prototype manipulation
grep -rn "\.prototype\." <pkg>/ | grep -v "Object.prototype"
grep -rn "setPrototypeOf" <pkg>/

# Regex lookbehind (Rust regex crate doesn't support)
grep -rn "(?<=\|(?<!" <pkg>/

# Computed property keys
grep -rn "^\s*\[.*\]:" <pkg>/ --include="*.ts"

Make a punch list. For each hit, decide: can it be patched, or does it rule the package out?

3. Triage

• Rules the package out: native addons, heavy eval/Function, packages whose core API needs exotic Proxy trap behavior beyond Perry's supported surface (full engine-level trapping of every dynamic access — see Limited Proxy Trapping). Plain Proxy use is fine.
• Patchable: decorators (often removable with a light rewrite), lookbehind regex (rewrite as a two-pass match), simple computed keys (hoist to explicit assignment), Object.setPrototypeOf in isomorphic fallback paths (often dead code for native targets).
• Defer to jsEval fallback if patching is unreasonable but only a small surface is affected.

Report the triage to the user before patching anything substantial, so they can decide whether to keep going.

4. Add to perry.compilePackages

Edit the project's package.json to include the package (and any transitive pure-TS/JS deps that also need porting):

{
  "perry": {
    "compilePackages": ["@noble/curves", "@noble/hashes"]
  }
}

5. Apply patches

Edit the package's files in node_modules/<name>/ to remove/rewrite the unsupported constructs. Keep the patches minimal and localized — the goal is a clean perry compile, not a refactor.

Record each patch in a new file perry-patches/<package>.md at the project root (create the directory if it doesn't exist) so the user can reapply them after npm install. Format: one H2 per patched file, show the before/after. This is the one piece of maintenance overhead Perry adds — call it out explicitly to the user.

6. Verify

Run a compile against a small file that imports the package:

perry compile <test.ts> -o /tmp/port-test && /tmp/port-test

If it fails, read the error. Compile-time errors will cite a file:line in the package — jump to it and patch. Runtime errors (e.g., undefined function) usually mean a stdlib API is missing; check docs/src/stdlib/ to see if Perry has the API under a different name.

7. Report

Tell the user:

• Which patches were applied (summary — the full record is in perry-patches/).
• Any gaps that couldn't be patched and are now jsEval-fallbacks (if any).
• Whether transitive deps also needed porting, and which ones.
• A warning if the package is going to need re-patching after every npm install — unless/until compilePackages gains a patch-file convention natively.

Important

• Don't patch blindly. A grep hit isn't always real — eval in a comment, Proxy as an identifier name, etc. Read the actual usage.
• Don't commit patches to the user's repo without asking. Show the diff, let them decide.
• Respect the experimental label. If something doesn't work, say so — don't paper over it. Report back so issue #115 gets real feedback.

Reference

• TS-subset gaps — docs/src/language/limitations.md
• Porting guide (human-readable, same content) — docs/src/packages/porting.md
• compilePackages reference — docs/src/getting-started/project-config.md
• JavaScript runtime fallback — docs/src/stdlib/overview.md (§ JavaScript Runtime Fallback)