0006. The handshake carries only the fields a mock has a source for

Status: Accepted · 2026-07-28 · #65 Governed by: 0000

TL;DR smocket populates the handshake fields it can derive from the connection itself: query, auth, time, issued, and url. The network-layer fields, headers, address, xdomain, and secure, have no source in a mock, so smocket leaves them rather than guess.

Decision

socket.handshake is populated selectively. This is the first concrete application of 0000: a field is filled when its value has a source in what smocket actually knows about the connection, and left otherwise.

The filled fields all come from the connection smocket sets up in memory.

• query and auth are the client's own inputs, passed to connect() and carried straight through, so their source is the caller.
• time and issued are the connection's timestamp, which smocket produces at the moment it completes the pairing, so it can supply them exactly.
• url is the normalized origin the client connected to, which smocket already holds as the registry key, so it is available with no invention.

query has two caller sources, the url's own query string and the options argument of connect(url, opts). When both are present the url wins and the options query is dropped wholesale; the options query is used only when the url carries none. This is not the intuitive rule, explicit options winning, so it was measured against socket.io-client 4.x rather than assumed: the real client uses the url query and ignores opts.query whole, and smocket matches, so a handler reads the same handshake.query on either engine.

The unfilled fields all describe a transport smocket does not have.

• headers and address are properties of a real HTTP request and a real remote peer. There is no request and no socket address in an in-memory pairing, so any value would be invented.
• xdomain and secure describe cross-origin and TLS state of a real network connection. A mock has neither a wire nor a certificate to read them from, so under 0000 they are left rather than defaulted to a plausible boolean.

The split follows a single line: what the caller and the mock's own bookkeeping supply is real and gets filled; what only a live network connection could answer has no source and is left.

Alternatives rejected

• Fill every field with a plausible default (empty headers, 127.0.0.1 for address, false for xdomain and secure). Each default reads as fact once in the object, and a test could come to depend on a value smocket made up, which is exactly the drift 0000 exists to prevent.
• Fill nothing and expose an empty handshake. This discards query, auth, and url, which do have a real source and which handlers legitimately read, so it throws away verifiable information to avoid inventing the rest.