__tests__/monitor.test.js

@@ -11,25 +11,30 @@ vi.mock("@actions/core", () => ({
   endGroup: vi.fn(),
 }));
 
-// ── mock @actions/artifact so tests never attempt real uploads ──────────────
+import * as artifact from "@actions/artifact";
 vi.mock("@actions/artifact", () => ({
-  DefaultArtifactClient: vi.fn().mockImplementation(() => ({
+  DefaultArtifactClient: class {
-    uploadArtifact: vi.fn().mockResolvedValue({}),
+    uploadArtifact() {
-  })),
+      return Promise.resolve({});
+    }
+  },
 }));
 
 import * as core from "@actions/core";
 import fs from "fs";
 import os from "os";
 import path from "path";
+import { DefaultArtifactClient } from "@actions/artifact";
 
 import {
   isOfficialServer,
   buildSubscribePath,
   detectTraceback,
   detectWarning,
+  outputMultiline,
   buildProgressMessage,
   writeLogFile,
+  uploadLogArtifacts,
   handleConsoleEvent,
   monitorConsole,
 } from "../monitor.js";
@@ -123,6 +128,33 @@ describe("detectWarning", () => {
   });
 });
 
+describe("outputMultiline", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("prefixes lines with shard when provided", () => {
+    outputMultiline("line1\nline2", "info", "shard0");
+    expect(core.info).toHaveBeenCalledWith("[shard0] line1");
+    expect(core.info).toHaveBeenCalledWith("[shard0] line2");
+  });
+
+  it("does not prefix when shard is missing", () => {
+    outputMultiline("line1", "info");
+    expect(core.info).toHaveBeenCalledWith("line1");
+  });
+
+  it("uses core.warning for level=warning", () => {
+    outputMultiline("warn", "warning", "s0");
+    expect(core.warning).toHaveBeenCalledWith("[s0] warn");
+  });
+
+  it("uses core.error for level=error", () => {
+    outputMultiline("err", "error", "s0");
+    expect(core.error).toHaveBeenCalledWith("[s0] err");
+  });
+});
+
 describe("buildProgressMessage", () => {
   it("formats correctly at 0 elapsed", () => {
     expect(buildProgressMessage(0, 50)).toBe("[Monitor] 0/50 ticks elapsed...");
@@ -141,48 +173,86 @@ describe("buildProgressMessage", () => {
   });
 });
 
+describe("uploadLogArtifacts", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it("instantiates DefaultArtifactClient and calls uploadArtifact", async () => {
+    const spy = vi.spyOn(
+      artifact.DefaultArtifactClient.prototype,
+      "uploadArtifact",
+    );
+    await uploadLogArtifacts(
+      ["/path/to/shard0_console_log.txt"],
+      "custom-name",
+    );
+    expect(spy).toHaveBeenCalledWith(
+      "custom-name",
+      ["/path/to/shard0_console_log.txt"],
+      "/path/to",
+    );
+  });
+
+  it("does nothing if filePaths is empty", async () => {
+    const spy = vi.spyOn(
+      artifact.DefaultArtifactClient.prototype,
+      "uploadArtifact",
+    );
+    await uploadLogArtifacts([]);
+    expect(spy).not.toHaveBeenCalled();
+  });
+});
+
 // ────────────────────────────────────────────────────────────────────────────
 // handleConsoleEvent
 // ────────────────────────────────────────────────────────────────────────────
 
 describe("handleConsoleEvent", () => {
   let state;
-  let stdoutBuffer;
+  let shardBuffers;
 
   beforeEach(() => {
     vi.clearAllMocks();
     state = { sawTraceback: false, sawErrorLog: false, sawWarningLog: false };
-    stdoutBuffer = [];
+    shardBuffers = {};
   });
 
   const makeEvent = (log = [], results = [], error = null) => ({
     data: { messages: { log, results }, error },
   });
 
-  it("calls core.info for each stdout line when logToFile=false", () => {
+  it("calls core.info for each stdout line with shard prefix when logToFile=false", () => {
-    const event = makeEvent(["line1", "line2"]);
+    const event = {
-    handleConsoleEvent(event, { logToFile: false }, stdoutBuffer, state);
+      data: {
-    expect(core.info).toHaveBeenCalledWith("line1");
+        shard: "shard0",
-    expect(core.info).toHaveBeenCalledWith("line2");
+        messages: { log: ["line1"], results: ["line2"] },
-    expect(stdoutBuffer).toHaveLength(0);
+      },
+    };
+    handleConsoleEvent(event, { logToFile: false }, shardBuffers, state);
+    expect(core.info).toHaveBeenCalledWith("[shard0] line1");
+    expect(core.info).toHaveBeenCalledWith("[shard0] line2");
+    expect(Object.keys(shardBuffers)).toHaveLength(0);
   });
 
   it("buffers stdout when logToFile=true; does not call core.info", () => {
-    const event = makeEvent(["line1", "line2"]);
+    const event = {
-    handleConsoleEvent(event, { logToFile: true }, stdoutBuffer, state);
+      data: { shard: "shard0", messages: { log: ["line1", "line2"] } },
+    };
+    handleConsoleEvent(event, { logToFile: true }, shardBuffers, state);
     expect(core.info).not.toHaveBeenCalled();
-    expect(stdoutBuffer).toEqual(["line1", "line2"]);
+    expect(shardBuffers["shard0"]).toEqual(["line1", "line2"]);
   });
 
   it("includes results lines in output", () => {
     const event = makeEvent([], ["result1"]);
-    handleConsoleEvent(event, { logToFile: false }, stdoutBuffer, state);
+    handleConsoleEvent(event, { logToFile: false }, shardBuffers, state);
     expect(core.info).toHaveBeenCalledWith("result1");
   });
 
   it("calls core.error when error field is non-empty", () => {
     const event = makeEvent([], [], "Script crashed");
-    handleConsoleEvent(event, { logToFile: false }, stdoutBuffer, state);
+    handleConsoleEvent(event, { logToFile: false }, shardBuffers, state);
     expect(core.error).toHaveBeenCalledWith("Script crashed");
     expect(state.sawErrorLog).toBe(true);
   });
@@ -190,58 +260,73 @@ describe("handleConsoleEvent", () => {
   it("sets state.sawTraceback when error contains stack frames", () => {
     const error = "TypeError: boom\n    at Object.<anonymous> (main:1:1)";
     const event = makeEvent([], [], error);
-    handleConsoleEvent(event, { logToFile: false }, stdoutBuffer, state);
+    handleConsoleEvent(event, { logToFile: false }, shardBuffers, state);
     expect(state.sawTraceback).toBe(true);
     expect(state.sawErrorLog).toBe(true);
   });
 
   it("does not set sawTraceback for plain error without stack frames", () => {
     const event = makeEvent([], [], "Script error: low CPU");
-    handleConsoleEvent(event, { logToFile: false }, stdoutBuffer, state);
+    handleConsoleEvent(event, { logToFile: false }, shardBuffers, state);
     expect(state.sawTraceback).toBe(false);
     expect(state.sawErrorLog).toBe(true);
   });
 
   it("sets state.sawWarningLog and calls core.warning for warn lines", () => {
     const event = makeEvent(["<font color='orange'>low energy</font>"]);
-    handleConsoleEvent(event, { logToFile: false }, stdoutBuffer, state);
+    handleConsoleEvent(event, { logToFile: false }, shardBuffers, state);
     expect(state.sawWarningLog).toBe(true);
     expect(core.warning).toHaveBeenCalled();
   });
 
   it("calls core.warning regardless of logToFile setting", () => {
     const event = makeEvent(["<font color='orange'>warn line</font>"]);
-    handleConsoleEvent(event, { logToFile: true }, stdoutBuffer, state);
+    handleConsoleEvent(event, { logToFile: true }, shardBuffers, state);
     expect(core.warning).toHaveBeenCalled();
   });
 
   it("handles missing messages gracefully (no crash on empty event)", () => {
     const event = { data: {} };
     expect(() =>
-      handleConsoleEvent(event, { logToFile: false }, stdoutBuffer, state),
+      handleConsoleEvent(event, { logToFile: false }, shardBuffers, state),
     ).not.toThrow();
   });
 
   it("handles completely empty event gracefully", () => {
     const event = {};
     expect(() =>
-      handleConsoleEvent(event, { logToFile: false }, stdoutBuffer, state),
+      handleConsoleEvent(event, { logToFile: false }, shardBuffers, state),
     ).not.toThrow();
   });
 
   it("filters messages by shard when targetShard is provided", () => {
     const event = { data: { shard: "shard0", messages: { log: ["msg0"] } } };
-    handleConsoleEvent(event, { shard: "shard1" }, stdoutBuffer, state);
+    handleConsoleEvent(event, { shard: "shard1" }, shardBuffers, state);
     expect(core.info).not.toHaveBeenCalled();
 
-    handleConsoleEvent(event, { shard: "shard0" }, stdoutBuffer, state);
+    handleConsoleEvent(event, { shard: "shard0" }, shardBuffers, state);
-    expect(core.info).toHaveBeenCalledWith("msg0");
+    expect(core.info).toHaveBeenCalledWith("[shard0] msg0");
   });
 
   it("does not filter when targetShard is undefined", () => {
     const event = { data: { shard: "shard0", messages: { log: ["msg0"] } } };
-    handleConsoleEvent(event, {}, stdoutBuffer, state);
+    handleConsoleEvent(event, {}, shardBuffers, state);
-    expect(core.info).toHaveBeenCalledWith("msg0");
+    expect(core.info).toHaveBeenCalledWith("[shard0] msg0");
+  });
+
+  it("buffers messages separately for different shards", () => {
+    const event0 = { data: { shard: "shard0", messages: { log: ["msg0"] } } };
+    const event1 = { data: { shard: "shard1", messages: { log: ["msg1"] } } };
+    handleConsoleEvent(event0, { logToFile: true }, shardBuffers, state);
+    handleConsoleEvent(event1, { logToFile: true }, shardBuffers, state);
+    expect(shardBuffers["shard0"]).toEqual(["msg0"]);
+    expect(shardBuffers["shard1"]).toEqual(["msg1"]);
+  });
+
+  it("uses 'default' key when shard is missing in event", () => {
+    const event = { data: { messages: { log: ["msg"] } } };
+    handleConsoleEvent(event, { logToFile: true }, shardBuffers, state);
+    expect(shardBuffers["default"]).toEqual(["msg"]);
   });
 });
 
@@ -519,4 +604,40 @@ describe("monitorConsole", () => {
     expect(result.sawTraceback).toBe(true);
     expect(result.sawErrorLog).toBe(true);
   });
+
+  it("creates separate log files for different shards when logToFile=true", async () => {
+    const api = buildMockApi({ ticks: [100, 101, 102, 103] });
+
+    setTimeout(() => {
+      api._fireConsole({
+        shard: "shard0",
+        messages: { log: ["msg0"], results: [] },
+        error: null,
+      });
+      api._fireConsole({
+        shard: "shard1",
+        messages: { log: ["msg1"], results: [] },
+        error: null,
+      });
+    }, 50);
+
+    // Verify uploadArtifact was called with two files
+    const spy = vi.spyOn(
+      artifact.DefaultArtifactClient.prototype,
+      "uploadArtifact",
+    );
+    await monitorConsole(api, {
+      ...BASE_OPTS,
+      logToFile: true,
+    });
+
+    expect(spy).toHaveBeenCalledWith(
+      "screeps-console-log",
+      expect.arrayContaining([
+        expect.stringContaining("shard0_console_log.txt"),
+        expect.stringContaining("shard1_console_log.txt"),
+      ]),
+      expect.any(String),
+    );
+  });
 });

monitor.js

@@ -88,17 +88,21 @@ export function safeDecode(text) {
 
 /**
  * Outputs text to the action log, splitting by newline to ensure proper display.
+ * Optionally prepends a [shard] prefix.
  *
  * @param {string} text
  * @param {"info"|"warning"|"error"} level
+ * @param {string} [shard]
  */
-export function outputMultiline(text, level = "info") {
+export function outputMultiline(text, level = "info", shard = null) {
   if (!text) return;
+  const prefix = shard ? `[${shard}] ` : "";
   const lines = text.split(/\r?\n/);
   lines.forEach((line) => {
-    if (level === "error") core.error(line);
+    const formattedLine = `${prefix}${line}`;
-    else if (level === "warning") core.warning(line);
+    if (level === "error") core.error(formattedLine);
-    else core.info(line);
+    else if (level === "warning") core.warning(formattedLine);
+    else core.info(formattedLine);
   });
 }
 
@@ -125,29 +129,27 @@ export async function writeLogFile(lines, filePath) {
 }
 
 /**
- * Uploads a file as a named workflow artifact using @actions/artifact.
+ * Uploads one or more files as a named workflow artifact using @actions/artifact.
  * Degrades gracefully to core.warning() if the runner does not support the
- * artifact service (e.g. a bare self-hosted runner without the service configured).
+ * artifact service.
  *
- * @param {string} filePath      - Absolute path of the file to upload
+ * @param {string[]} filePaths   - Absolute paths of the files to upload
  * @param {string}   [artifactName="screeps-console-log"] - Artifact display name
  * @returns {Promise<void>}
  */
-export async function uploadLogArtifact(
+export async function uploadLogArtifacts(
-  filePath,
+  filePaths,
   artifactName = "screeps-console-log",
 ) {
+  if (!filePaths || filePaths.length === 0) return;
   try {
     const client = new DefaultArtifactClient();
-    await client.uploadArtifact(
+    const rootDir = path.dirname(filePaths[0]);
-      artifactName,
+    await client.uploadArtifact(artifactName, filePaths, rootDir);
-      [filePath],
+    core.info(`[Monitor] Console logs uploaded as artifact '${artifactName}'.`);
-      path.dirname(filePath),
-    );
-    core.info(`[Monitor] Console log uploaded as artifact '${artifactName}'.`);
   } catch (err) {
     core.warning(
-      `[Monitor] Could not upload console log as artifact: ${err.message}`,
+      `[Monitor] Could not upload console logs as artifact: ${err.message}`,
     );
   }
 }
@@ -173,12 +175,12 @@ export async function uploadLogArtifact(
  *   - All stdout lines → core.info() when logToFile=false,
  *                        pushed to stdoutBuffer when logToFile=true.
  *
- * @param {{ data?: { messages?: { log?: string[], results?: string[] }, error?: string } }} event
+ * @param {{ data?: { messages?: { log?: string[], results?: string[] }, error?: string, shard?: string } }} event
- * @param {{ logToFile: boolean }} opts
+ * @param {{ logToFile: boolean, shard?: string }} opts
- * @param {string[]} stdoutBuffer - Mutable buffer used in logToFile mode
+ * @param {Record<string, string[]>} shardBuffers - Mutable buffer Map used in logToFile mode
  * @param {{ sawTraceback: boolean, sawErrorLog: boolean, sawWarningLog: boolean }} state
  */
-export function handleConsoleEvent(event, opts, stdoutBuffer, state) {
+export function handleConsoleEvent(event, opts, shardBuffers, state) {
   const { logToFile, shard: targetShard } = opts;
   const data = event?.data ?? {};
 
@@ -198,7 +200,7 @@ export function handleConsoleEvent(event, opts, stdoutBuffer, state) {
     const warnPattern = /<font\s+color=['"](?:orange|yellow)['"]/i;
     logLines
       .filter((l) => warnPattern.test(l))
-      .forEach((l) => outputMultiline(safeDecode(l), "warning"));
+      .forEach((l) => outputMultiline(safeDecode(l), "warning", data.shard));
   }
 
   // Traceback detection in log lines (Screeps sometimes sends errors here)
@@ -211,9 +213,11 @@ export function handleConsoleEvent(event, opts, stdoutBuffer, state) {
   const allStdout = [...logLines, ...results].map(safeDecode);
   if (allStdout.length > 0) {
     if (logToFile) {
-      stdoutBuffer.push(...allStdout);
+      const shard = data.shard || "default";
+      if (!shardBuffers[shard]) shardBuffers[shard] = [];
+      shardBuffers[shard].push(...allStdout);
     } else {
-      allStdout.forEach((l) => outputMultiline(l, "info"));
+      allStdout.forEach((l) => outputMultiline(l, "info", data.shard));
     }
   }
 
@@ -221,7 +225,7 @@ export function handleConsoleEvent(event, opts, stdoutBuffer, state) {
   if (errorText) {
     state.sawErrorLog = true;
     const decodedError = safeDecode(errorText);
-    outputMultiline(decodedError, "error");
+    outputMultiline(decodedError, "error", data.shard);
     if (detectTraceback(decodedError)) {
       state.sawTraceback = true;
     }
@@ -322,7 +326,7 @@ export async function monitorConsole(api, opts) {
   const subscribePath = buildSubscribePath(hostname, providedShard);
 
   // Shared mutable state — updated by handleConsoleEvent via event listener
-  const stdoutBuffer = [];
+  const shardBuffers = {}; // { [shardName]: string[] }
   const state = {
     sawTraceback: false,
     sawErrorLog: false,
@@ -336,7 +340,7 @@ export async function monitorConsole(api, opts) {
   // Step 2: connect socket + subscribe
   await api.socket.connect();
   await api.socket.subscribe(subscribePath, (event) => {
-    handleConsoleEvent(event, opts, stdoutBuffer, state);
+    handleConsoleEvent(event, opts, shardBuffers, state);
   });
 
   core.info(
@@ -378,13 +382,24 @@ export async function monitorConsole(api, opts) {
   }
 
   // Step 6: artifact upload
-  if (logToFile && stdoutBuffer.length > 0) {
+  const shardKeys = Object.keys(shardBuffers);
+  if (logToFile && shardKeys.length > 0) {
     const tmpDir = await fs.promises.mkdtemp(
       path.join(os.tmpdir(), "screeps-monitor-"),
     );
-    const tmpFile = path.join(tmpDir, "screeps_console_log.txt");
+    const filePaths = [];
-    await writeLogFile(stdoutBuffer, tmpFile);
+
-    await uploadLogArtifact(tmpFile);
+    for (const sName of shardKeys) {
+      const fileName =
+        sName === "default"
+          ? "screeps_console_log.txt"
+          : `${sName}_console_log.txt`;
+      const tmpFile = path.join(tmpDir, fileName);
+      await writeLogFile(shardBuffers[sName], tmpFile);
+      filePaths.push(tmpFile);
+    }
+
+    await uploadLogArtifacts(filePaths);
   } else if (logToFile) {
     core.info(
       "[Monitor] No stdout lines were collected; skipping artifact upload.",