co-mono/packages/coding-agent/test/compaction-hooks-example.test.ts

/**
 * Verify the documentation example from hooks.md compiles and works.
 */

import { describe, expect, it } from "vitest";
import type { HookAPI } from "../src/core/hooks/index.js";

describe("Documentation example", () => {
	it("custom compaction example should type-check correctly", () => {
		// This is the example from hooks.md - verify it compiles
		const exampleHook = (pi: HookAPI) => {
			pi.on("session", async (event, _ctx) => {
				if (event.reason !== "before_compact") return;

				// After narrowing, these should all be accessible
				const { preparation, previousCompactions, sessionManager, modelRegistry, model } = event;
				const { messagesToSummarize, messagesToKeep, tokensBefore, firstKeptEntryId, cutPoint } = preparation;

				// Get previous summary from most recent compaction
				const _previousSummary = previousCompactions[0]?.summary;

				// Verify types
				expect(Array.isArray(messagesToSummarize)).toBe(true);
				expect(Array.isArray(messagesToKeep)).toBe(true);
				expect(typeof cutPoint.firstKeptEntryIndex).toBe("number");
				expect(typeof tokensBefore).toBe("number");
				expect(model).toBeDefined();
				expect(typeof sessionManager.getEntries).toBe("function");
				expect(typeof modelRegistry.getApiKey).toBe("function");
				expect(typeof firstKeptEntryId).toBe("string");

				const summary = messagesToSummarize
					.filter((m) => m.role === "user")
					.map((m) => `- ${typeof m.content === "string" ? m.content.slice(0, 100) : "[complex]"}`)
					.join("\n");

				// Hooks return compaction content - SessionManager adds id/parentId
				return {
					compaction: {
						summary: `User requests:\n${summary}`,
						firstKeptEntryId,
						tokensBefore,
					},
				};
			});
		};

		// Just verify the function exists and is callable
		expect(typeof exampleHook).toBe("function");
	});

	it("compact event should have correct fields after narrowing", () => {
		const checkCompactEvent = (pi: HookAPI) => {
			pi.on("session", async (event, _ctx) => {
				if (event.reason !== "compact") return;

				// After narrowing, these should all be accessible
				const entry = event.compactionEntry;
				const fromHook = event.fromHook;

				expect(entry.type).toBe("compaction");
				expect(typeof entry.summary).toBe("string");
				expect(typeof entry.tokensBefore).toBe("number");
				expect(typeof fromHook).toBe("boolean");
			});
		};

		expect(typeof checkCompactEvent).toBe("function");
	});
});