e2e: add self-host coverage for emit() content blocks (#1592) (#1820)

Author: RhysSullivan

e2e/selfhost/execute-emit-envelope.test.ts

@@ -0,0 +1,94 @@
+// Selfhost: emit() output actually reaches the MCP client's content blocks,
+// not merely the `emitted` count in the envelope. Regression coverage for
+// issue #1592 — a self-hosted user saw a non-zero `emitted` count but no
+// content blocks in the tool result, only `logs` and the return value. There
+// is cloud coverage for the envelope count
+// (`e2e/cloud/execute-emit-envelope.test.ts`), but nothing that asserts on
+// the wire-level `content` array on self-host, and nothing on either target
+// that covers all three emit shapes from the report: a plain string, a
+// ToolFile, and a structured/object value.
+import { expect } from "@effect/vitest";
+import { Effect } from "effect";
+
+import { scenario } from "../src/scenario";
+import { Mcp, Target } from "../src/services";
+
+interface ContentBlock {
+  readonly type: string;
+  readonly text?: string;
+}
+
+// Mirrors the issue's repro exactly: a plain string emit, a ToolFile emit, a
+// structured/object emit, then a return.
+const EXECUTE_CODE = `
+const attachment = {
+  _tag: "ToolFile",
+  name: "report.txt",
+  mimeType: "text/plain",
+  encoding: "base64",
+  data: "aGVsbG8gZmlsZQ==",
+  byteLength: 10,
+};
+emit("plain string emit");
+emit(attachment);
+emit({ hello: "object emit" });
+return { returnedValue: "this is the return" };
+`;
+
+scenario(
+  "Execute · emit() output reaches the MCP client's content blocks",
+  {},
+  Effect.gen(function* () {
+    const target = yield* Target;
+    const mcp = yield* Mcp;
+    const identity = yield* target.newIdentity();
+    const session = mcp.session(identity);
+
+    const result = yield* session.call("execute", { code: EXECUTE_CODE });
+    expect(result.ok, `execute completed (got: ${result.text.slice(0, 300)})`).toBe(true);
+
+    const structured = (result.raw as { structuredContent?: Record<string, unknown> })
+      .structuredContent;
+    expect(structured?.status, "the run completed").toBe("completed");
+    expect(structured?.emitted, "the envelope counts all three emitted items").toBe(3);
+    expect(structured?.result, "the return value still comes back to the caller").toEqual({
+      returnedValue: "this is the return",
+    });
+
+    // The real assertion: the JSON-RPC tool result's `content` array — what
+    // an MCP client actually renders — carries all three emitted items, not
+    // just the `emitted` count.
+    const content = (result.raw as { content?: ContentBlock[] }).content ?? [];
+    expect(Array.isArray(content) && content.length > 0, "the wire result carries content").toBe(
+      true,
+    );
+
+    expect(
+      content.some((block) => block.type === "text" && block.text === "plain string emit"),
+      `content carries the plain string emit; got: ${JSON.stringify(content)}`,
+    ).toBe(true);
+
+    // A text-mimetype ToolFile renders as a summary line plus its decoded
+    // text content (see outputFileContent/toolFileContent in tool-server.ts).
+    expect(
+      content.some(
+        (block) =>
+          block.type === "text" &&
+          typeof block.text === "string" &&
+          block.text.includes("report.txt"),
+      ),
+      `content carries the ToolFile emit's summary line; got: ${JSON.stringify(content)}`,
+    ).toBe(true);
+    expect(
+      content.some((block) => block.type === "text" && block.text === "hello file"),
+      `content carries the ToolFile emit's decoded text; got: ${JSON.stringify(content)}`,
+    ).toBe(true);
+
+    // A plain object emit is not a ToolFile or an MCP content block, so it
+    // falls back to a JSON text block.
+    expect(
+      content.some((block) => block.type === "text" && block.text === '{"hello":"object emit"}'),
+      `content carries the structured/object emit; got: ${JSON.stringify(content)}`,
+    ).toBe(true);
+  }),
+);