chore: import upstream snapshot with attribution

tests/unit/build/opencode-plugin-esm-only.test.ts

@@ -0,0 +1,65 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { fileURLToPath } from "node:url";
+
+// Regression guard for #3883: the @omniroute/opencode-plugin must ship an
+// ESM-only bundle. OpenCode's Bun-based plugin loader resolves the package
+// `main`/`exports` and applies CJS-to-ESM interop on a dual CJS bundle, which
+// turns `mod.default` into the whole exports namespace, fails V1 plugin
+// detection, and makes the loader throw "Plugin export is not a function".
+// Shipping ESM-only (with a `./runtime` subpath) keeps `mod.default` the V1
+// plugin object so the loader registers it. Do NOT re-introduce a CJS bundle.
+
+const PKG_URL = new URL("../../../@omniroute/opencode-plugin/package.json", import.meta.url);
+const TSUP_URL = new URL("../../../@omniroute/opencode-plugin/tsup.config.ts", import.meta.url);
+
+function readJson(url: URL): Record<string, unknown> {
+  return JSON.parse(readFileSync(fileURLToPath(url), "utf8"));
+}
+
+test("opencode-plugin package.json ships ESM-only (no CJS bundle)", () => {
+  const pkg = readJson(PKG_URL);
+
+  // main must point at the ESM build, never the .cjs bundle.
+  assert.equal(pkg.main, "./dist/index.js", "main must be the ESM build");
+  assert.equal(
+    typeof pkg.main === "string" && pkg.main.endsWith(".cjs"),
+    false,
+    "main must not be a .cjs bundle"
+  );
+  // The legacy dual-bundle `module` field should be gone.
+  assert.equal("module" in pkg, false, "the dual-bundle `module` field must be removed");
+
+  const exports = pkg.exports as Record<string, unknown> | undefined;
+  assert.ok(exports && typeof exports === "object", "exports map must exist");
+
+  const root = exports["."] as Record<string, unknown>;
+  assert.ok(root && typeof root === "object", 'exports["."] must exist');
+  assert.equal(root.import, "./dist/index.js", 'exports["."].import must be the ESM build');
+  // A `require` condition would re-introduce the CJS path the loader chokes on.
+  assert.equal("require" in root, false, 'exports["."] must not declare a `require` condition');
+
+  // The `./runtime` subpath used by the OpenCode loader must resolve to ESM.
+  const runtime = exports["./runtime"] as Record<string, unknown>;
+  assert.ok(runtime && typeof runtime === "object", 'exports["./runtime"] must exist');
+  assert.equal(runtime.import, "./dist/index.js", 'exports["./runtime"].import must be ESM');
+});
+
+test("opencode-plugin tsup config builds ESM-only with cjsInterop disabled", () => {
+  const tsup = readFileSync(fileURLToPath(TSUP_URL), "utf8");
+
+  const formatMatch = tsup.match(/format:\s*\[([^\]]*)\]/);
+  assert.ok(formatMatch, "tsup config must declare a format array");
+  const formats = formatMatch[1]
+    .split(",")
+    .map((s) => s.trim().replace(/['"]/g, ""))
+    .filter(Boolean);
+  assert.deepEqual(formats, ["esm"], "tsup must build esm only (no cjs)");
+
+  assert.equal(
+    /cjsInterop:\s*true/.test(tsup),
+    false,
+    "cjsInterop must not be true for an ESM-only build"
+  );
+});