improvise/web/tests/bundle/wasm_surface.test.js

// The JS↔wasm boundary: every call the page makes is declared by the bundle,
// with the arity it declares. Needs `web/build.sh` to have run.

import { test } from "node:test";
import assert from "node:assert/strict";
import { readFileSync } from "node:fs";
import { fileURLToPath } from "node:url";

const web = (name) => fileURLToPath(new URL(`../../${name}`, import.meta.url));

/// Declared methods and free functions, as `name -> [min, max]` arity. A
/// missing bundle is a FAILURE and never a skip: this file exists to be run
/// after `web/build.sh`, and a silent pass would report exactly nothing.
function declarations(dts) {
  const text = readFileSync(web(dts), "utf8");
  const found = new Map();
  const decl = /(?:^|\n)\s*(?:export function |static )?([a-z_][A-Za-z0-9_]*)\(([^)]*)\)\s*:/g;
  for (const [, name, params] of text.matchAll(decl)) {
    const list = params.trim() === "" ? [] : params.split(",");
    const required = list.filter((p) => !p.includes("?:")).length;
    found.set(name, [required, list.length]);
  }
  assert.ok(found.size > 0, `${dts} declares nothing — was web/build.sh run?`);
  return found;
}

/// Every `<receiver>.<name>(...)` call in a source file, with how many
/// top-level arguments it passes.
function callsOn(file, receiver) {
  const text = readFileSync(web(file), "utf8");
  const calls = [];
  const head = new RegExp(`${receiver}\\.([a-z_][A-Za-z0-9_]*)\\(`, "g");
  for (const match of text.matchAll(head)) {
    let depth = 1;
    let i = match.index + match[0].length;
    let commas = 0;
    let body = "";
    while (depth > 0 && i < text.length) {
      const ch = text[i];
      if ("([{".includes(ch)) depth += 1;
      else if (")]}".includes(ch)) depth -= 1;
      else if (ch === "," && depth === 1) commas += 1;
      if (depth > 0) body += ch;
      i += 1;
    }
    assert.equal(depth, 0, `unbalanced call to ${match[1]} in ${file}`);
    calls.push({ name: match[1], args: body.trim() === "" ? 0 : commas + 1 });
  }
  return calls;
}

test("every client call web/app.js makes is declared, with that arity", () => {
  const declared = declarations("pkg/improvise_wasm_client.d.ts");
  const calls = callsOn("app.js", "client");
  assert.ok(calls.length >= 6, `found only ${calls.length} client calls`);
  for (const call of calls) {
    const arity = declared.get(call.name);
    assert.ok(arity, `web/app.js calls client.${call.name}, which the bundle does not declare`);
    const [min, max] = arity;
    assert.ok(
      call.args >= min && call.args <= max,
      `client.${call.name} takes ${min}..${max} arguments; app.js passes ${call.args}`,
    );
  }
});

test("the page still reaches the client through a handful of calls", () => {
  const names = new Set(callsOn("app.js", "client").map((c) => c.name));
  // The named surface, so a call added without an argument fails here and
  // has to come and say so. `viewport` is deliberately absent: `set_viewport`
  // is the one that records the window (gotcha 47).
  assert.deepEqual(
    [...names].sort(),
    [
      "click_category",
      "click_cell",
      "click_formula",
      "click_tile",
      "click_view",
      "on_frame",
      "on_key_event",
      "render_model",
      "set_viewport",
      "typed_cell",
    ],
  );
});

/// Methods on `Client` the page does not call, each with the reason it is
/// still exported. A door with no caller and no entry here is improvise-seik:
/// the dangerous kind, because calling the wrong one of a pair is silent.
const UNCALLED = {
  free: "wasm-bindgen's own destructor, not ours to remove",
  initSync: "wasm-bindgen's own module loader, beside the default export",
  revision: "on_frame returns it; a page that stores it can skip a repaint",
};

test("the bundle exports no client door the page has no reason to hold", () => {
  const declared = declarations("pkg/improvise_wasm_client.d.ts");
  const called = new Set(callsOn("app.js", "client").map((c) => c.name));
  // `constructor` is `new Client()`, which `callsOn` cannot see as a call.
  const spare = [...declared.keys()].filter(
    (name) => name !== "constructor" && !called.has(name),
  );
  assert.deepEqual(
    spare.sort(),
    Object.keys(UNCALLED).sort(),
    "an exported method nothing calls — delete it, or add it to UNCALLED with the reason",
  );
});

test("every worker call web/worker.js makes is declared, with that arity", () => {
  const declared = declarations("worker-pkg/improvise_worker_server.d.ts");
  const calls = callsOn("worker.js", "server");
  assert.ok(calls.length >= 2, `found only ${calls.length} server calls`);
  for (const call of calls) {
    const arity = declared.get(call.name);
    assert.ok(arity, `web/worker.js calls server.${call.name}, undeclared by the bundle`);
    assert.ok(
      call.args >= arity[0] && call.args <= arity[1],
      `server.${call.name} takes ${arity[0]}..${arity[1]}; worker.js passes ${call.args}`,
    );
  }
  // `start` is a free function rather than a method, and takes the seed.
  assert.deepEqual(declared.get("start"), [1, 2]);
});