`tty.ReadStream` / `tty.WriteStream` class exports undefined; `stdout.isTTY` typeof is boolean when piped

[proggeramlug]

Repro

import * as tty from "node:tty";
console.log("tty.ReadStream typeof:", typeof tty.ReadStream);
console.log("tty.WriteStream typeof:", typeof tty.WriteStream);
console.log("tty.isatty typeof:", typeof tty.isatty);
console.log("tty.isatty(0):", tty.isatty(0));
console.log("process.stdout.isTTY typeof:", typeof process.stdout.isTTY);

Actual (Perry v0.5.894, with stdout piped to a file)

tty.ReadStream typeof: undefined
tty.WriteStream typeof: undefined
tty.isatty typeof: undefined
tty.isatty(0): false
process.stdout.isTTY typeof: boolean

Expected (Node, with stdout piped to a file)

tty.ReadStream typeof: function
tty.WriteStream typeof: function
tty.isatty typeof: function
tty.isatty(0): false
process.stdout.isTTY typeof: undefined

Three bugs

1. tty.ReadStream / tty.WriteStream class exports return undefined

The classes aren't exposed as properties on the tty namespace object. Code that does instanceof tty.ReadStream or checks typeof tty.WriteStream === "function" (common pattern for "is this a TTY stream?") fails.

2. tty.isatty typeof returns undefined even though calling it works

Subtle: typeof tty.isatty returns "undefined" but the call tty.isatty(0) works correctly and returns false. So Perry has the dispatch path wired for the call (probably via NATIVE_MODULE_TABLE) but the property-access path (typeof) doesn't see the function. Same family as #629 — namespace member visibility is incomplete.

3. process.stdout.isTTY typeof returns "boolean" instead of "undefined" when stdout is not a TTY

Per the Node spec: isTTY is true when the stream is a TTY, undefined otherwise (intentionally — it's a presence-test). Perry returns false (typeof boolean) when piped, which is a small but spec-divergent behavior.

Many libraries do if (process.stdout.isTTY) { ... } (truthy check works the same either way) but some do if ("isTTY" in process.stdout) or if (process.stdout.isTTY !== undefined) — those fail under Perry.

Impact

These are the entire remaining diff in test-files/test_parity_tty.ts (3 lines off Node). Fix them and the parity test reaches full byte-for-byte PASS — joining test_parity_os and (potentially) test_parity_path (#741) as the third module to fully match.

Acceptance

The 5-line repro prints output matching Node when stdout is piped.

Related

• Continuation of Namespace import for unrecognized node:* sub-paths resolves to true (TAG_TRUE) #629 (namespace property visibility — same root cause family).
• Surfaced via test-files/test_parity_tty.ts (diff = 6 in v0.5.894 sweep).