node:crypto: expose DiffieHellman constructor exports

[andrewtdiz]

Summary

Node exposes crypto.DiffieHellman and crypto.DiffieHellmanGroup as enumerable callable constructor exports. Perry has createDiffieHellman, createDiffieHellmanGroup, and getDiffieHellman factory coverage and DH handle support, but the class constructor exports themselves are missing from the manifest/declarations.

This is a narrower export-shape gap than expanding DH algorithm behavior.

Node behavior

On local Node v25.9.0:

const crypto = require("node:crypto");

Object.keys(crypto).includes("DiffieHellman"); // true
Object.keys(crypto).includes("DiffieHellmanGroup"); // true

typeof crypto.DiffieHellman; // "function"
crypto.DiffieHellman.length; // 4

typeof crypto.DiffieHellmanGroup; // "function"
crypto.DiffieHellmanGroup.length; // 1

new crypto.DiffieHellman(512).generateKeys; // function
crypto.DiffieHellman(512).computeSecret; // function
new crypto.DiffieHellmanGroup("modp5").getPrime; // function
crypto.DiffieHellmanGroup("modp5").generateKeys; // function

Both constructors are callable with and without new.

Current Perry evidence

Current origin/main has factory/handle coverage but not the constructor exports:

• crates/perry-api-manifest/src/entries.rs registers crypto.createDiffieHellman, crypto.createDiffieHellmanGroup, and crypto.getDiffieHellman, but no class("crypto", "DiffieHellman"), class("crypto", "DiffieHellmanGroup"), or callable method entries for those constructor names.
• crates/perry-codegen/src/expr/calls.rs lowers the factory helpers to DH runtime calls.
• crates/perry-stdlib/src/crypto/ecdh.rs and handles.rs implement DiffieHellmanHandle behavior used by those factories.
• docs/runtime-parity.md marks class crypto.DiffieHellman and class crypto.DiffieHellmanGroup covered.
• docs/api/perry.d.ts declares the factory helpers but no DiffieHellman / DiffieHellmanGroup classes or callable constructors.

Suggested test surface

Add granular crypto inventory/constructor fixtures that check:

• Object.keys(require("node:crypto")) includes DiffieHellman and DiffieHellmanGroup
• typeof crypto.DiffieHellman === "function" and typeof crypto.DiffieHellmanGroup === "function"
• constructor and callable forms delegate to the same handle behavior as createDiffieHellman(...) / createDiffieHellmanGroup(...)
• named imports bind: import { DiffieHellman, DiffieHellmanGroup } from "node:crypto"

Scope / non-goals

This is scoped to the two DH constructor exports and their delegation to the existing DH factory/handle paths. It does not cover additional DH algorithm coverage, exact OpenSSL error text, crypto stream semantics (#2479), KeyObject gaps (#2565), or argument validation (#2013).

No local target/release/perry binary was available for a compiled runtime repro; this issue is based on Node probes plus current origin/main source inspection.

[andrewtdiz]

I’m taking this as part of a focused node:crypto public export/manifest parity cut with #2694 and #2716. Planned scope: expose the DiffieHellman/DiffieHellmanGroup constructor aliases through the same public namespace/manifest path as the existing DH factories, with focused parity coverage.

[andrewtdiz]

Draft PR opened for this crypto export cluster: #4123