feat: add compaction prompt plugin

test/index.test.ts

@@ -0,0 +1,136 @@
+import { afterEach, describe, expect, test } from "bun:test";
+import { mkdir, mkdtemp, rm, writeFile } from "node:fs/promises";
+import os from "node:os";
+import path from "node:path";
+import { CompactionPromptPlugin } from "../src/index.js";
+
+const temporaryDirectories: string[] = [];
+
+afterEach(async (): Promise<void> => {
+  await Promise.all(
+    temporaryDirectories
+      .splice(0)
+      .map((directory) => rm(directory, { recursive: true })),
+  );
+});
+
+async function createContext(): Promise<{
+  worktree: string;
+  logs: Array<unknown>;
+  client: { app: { log: (input: unknown) => Promise<void> } };
+}> {
+  const worktree = await mkdtemp(
+    path.join(os.tmpdir(), "opencode-compaction-"),
+  );
+  temporaryDirectories.push(worktree);
+  const logs: Array<unknown> = [];
+
+  return {
+    worktree,
+    logs,
+    client: {
+      app: {
+        log: async (input: unknown): Promise<void> => {
+          logs.push(input);
+        },
+      },
+    },
+  };
+}
+
+describe("CompactionPromptPlugin", () => {
+  test("appends instructions and memory by default", async () => {
+    const context = await createContext();
+    await mkdir(path.join(context.worktree, ".opencode"));
+    await writeFile(
+      path.join(context.worktree, ".opencode/compaction.md"),
+      "Keep the active hypothesis.",
+    );
+    const hooks = await CompactionPromptPlugin(context as never);
+    const output = { context: [] as string[] };
+
+    await hooks["experimental.session.compacting"]?.(
+      { sessionID: "test" },
+      output,
+    );
+
+    expect(output.context[0]).toContain("Keep the active hypothesis.");
+    expect(output.context[0]).toContain("Custom compaction request honored.");
+  });
+
+  test("combines custom instructions with a configured memory file", async () => {
+    const context = await createContext();
+    await writeFile(
+      path.join(context.worktree, "project-memory.md"),
+      "Preserve the active hypothesis.",
+    );
+    const hooks = await CompactionPromptPlugin(context as never, {
+      memoryFile: "project-memory.md",
+      prompt: "Keep exact file paths.",
+      completionMarker: "Compaction complete.",
+    });
+    const output = { context: ["Existing context"] };
+
+    await hooks["experimental.session.compacting"]?.(
+      { sessionID: "test" },
+      output,
+    );
+
+    expect(output.context).toHaveLength(2);
+    expect(output.context[0]).toBe("Existing context");
+    expect(output.context[1]).toContain("Keep exact file paths.");
+    expect(output.context[1]).toContain("Preserve the active hypothesis.");
+    expect(output.context[1]).toContain("Compaction complete.");
+  });
+
+  test("supports replacing the default prompt", async () => {
+    const context = await createContext();
+    const hooks = await CompactionPromptPlugin(context as never, {
+      mode: "replace",
+      prompt: "Preserve the current implementation plan.",
+    });
+    const output: { context: string[]; prompt?: string } = { context: [] };
+
+    await hooks["experimental.session.compacting"]?.(
+      { sessionID: "test" },
+      output,
+    );
+
+    expect(output.prompt).toContain("User Compaction Instructions");
+    expect(output.prompt).toContain(
+      "Preserve the current implementation plan.",
+    );
+    expect(output.context).toHaveLength(0);
+  });
+
+  test("ignores a missing memory file", async () => {
+    const context = await createContext();
+    const hooks = await CompactionPromptPlugin(context as never);
+    const output = { context: [] as string[] };
+
+    await hooks["experimental.session.compacting"]?.(
+      { sessionID: "test" },
+      output,
+    );
+
+    expect(context.logs).toHaveLength(0);
+    expect(output.context).toHaveLength(1);
+  });
+
+  test("logs non-missing memory file errors without failing compaction", async () => {
+    const context = await createContext();
+    await writeFile(path.join(context.worktree, "memory"), "not a directory");
+    const hooks = await CompactionPromptPlugin(context as never, {
+      memoryFile: "memory/file.md",
+    });
+    const output = { context: [] as string[] };
+
+    await hooks["experimental.session.compacting"]?.(
+      { sessionID: "test" },
+      output,
+    );
+
+    expect(context.logs).toHaveLength(1);
+    expect(output.context).toHaveLength(1);
+  });
+});