feat: increase logging in copilot driver for silent startup failures

actions/setup/js/copilot_driver.cjs

@@ -25,6 +25,7 @@
 "use strict";
 
 const { spawn } = require("child_process");
+const fs = require("fs");
 
 // Maximum number of retry attempts after the initial run
 const MAX_RETRIES = 3;
@@ -67,6 +68,29 @@ function sleep(ms) {
   return new Promise(resolve => setTimeout(resolve, ms));
 }
 
+/**
+ * Check whether a command path is accessible and executable, logging the result.
+ * Returns true if the command is usable, false otherwise.
+ * @param {string} command - Absolute or relative path to the executable
+ * @returns {Promise<boolean>}
+ */
+async function checkCommandAccessible(command) {
+  try {
+    await fs.promises.access(command, fs.constants.F_OK);
+  } catch {
+    log(`pre-flight: command not found: ${command} (F_OK check failed — binary does not exist at this path)`);
+    return false;
+  }
+  try {
+    await fs.promises.access(command, fs.constants.X_OK);
+    log(`pre-flight: command is accessible and executable: ${command}`);
+    return true;
+  } catch {
+    log(`pre-flight: command exists but is not executable: ${command} (X_OK check failed — permission denied)`);
+    return false;
+  }
+}
+
 /**
  * Format elapsed milliseconds as a human-readable string (e.g. "3m 12s").
  * @param {number} ms
@@ -148,7 +172,10 @@ function runProcess(command, args, attempt) {
 
     child.on("error", err => {
       const durationMs = Date.now() - startTime;
-      log(`attempt ${attempt + 1}: failed to start process '${command}': ${err.message}`);
+      const errno = /** @type {NodeJS.ErrnoException} */ err;
+      const errCode = errno.code ?? "unknown";
+      const errSyscall = errno.syscall ?? "unknown";
+      log(`attempt ${attempt + 1}: failed to start process '${command}': ${err.message}` + ` (code=${errCode} syscall=${errSyscall})`);
       resolve({
         exitCode: 1,
         output: collectedOutput,
@@ -170,7 +197,9 @@ async function main() {
     process.exit(1);
   }
 
-  log(`starting: command=${command} maxRetries=${MAX_RETRIES} initialDelayMs=${INITIAL_DELAY_MS} backoffMultiplier=${BACKOFF_MULTIPLIER} maxDelayMs=${MAX_DELAY_MS}`);
+  log(`starting: command=${command} maxRetries=${MAX_RETRIES} initialDelayMs=${INITIAL_DELAY_MS}` + ` backoffMultiplier=${BACKOFF_MULTIPLIER} maxDelayMs=${MAX_DELAY_MS}` + ` nodeVersion=${process.version} platform=${process.platform}`);
+
+  await checkCommandAccessible(command);
 
   let delay = INITIAL_DELAY_MS;
   let lastExitCode = 1;
@@ -212,7 +241,7 @@ async function main() {
     if (attempt >= MAX_RETRIES) {
       log(`all ${MAX_RETRIES} retries exhausted — giving up (exitCode=${lastExitCode})`);
     } else {
-      log(`attempt ${attempt + 1}: no output produced — not retrying (process may have failed to start)`);
+      log(`attempt ${attempt + 1}: no output produced — not retrying` + ` (possible causes: binary not found, permission denied, auth failure, or silent startup crash)`);
     }
 
     // Non-retryable error or retries exhausted — propagate exit code

actions/setup/js/copilot_driver.test.cjs

@@ -153,4 +153,35 @@ describe("copilot_driver.cjs", () => {
       expect(logLine).toMatch(/^\[copilot-driver\] \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}/);
     });
   });
+
+  describe("startup log includes node version and platform", () => {
+    it("starting log line contains nodeVersion and platform fields", () => {
+      const command = "/usr/local/bin/copilot";
+      const startingLine = `starting: command=${command} maxRetries=3 initialDelayMs=5000` + ` backoffMultiplier=2 maxDelayMs=60000` + ` nodeVersion=${process.version} platform=${process.platform}`;
+      expect(startingLine).toContain("nodeVersion=");
+      expect(startingLine).toContain("platform=");
+      expect(startingLine).toMatch(/nodeVersion=v\d+\.\d+/);
+    });
+  });
+
+  describe("no-output failure message", () => {
+    it("includes actionable possible causes", () => {
+      const msg = `attempt 1: no output produced — not retrying` + ` (possible causes: binary not found, permission denied, auth failure, or silent startup crash)`;
+      expect(msg).toContain("binary not found");
+      expect(msg).toContain("permission denied");
+      expect(msg).toContain("auth failure");
+      expect(msg).toContain("silent startup crash");
+    });
+  });
+
+  describe("error event message", () => {
+    it("includes code and syscall fields", () => {
+      const errMessage = "spawn /usr/local/bin/copilot ENOENT";
+      const errCode = "ENOENT";
+      const errSyscall = "spawn";
+      const logMsg = `attempt 1: failed to start process '/usr/local/bin/copilot': ${errMessage}` + ` (code=${errCode} syscall=${errSyscall})`;
+      expect(logMsg).toContain("code=ENOENT");
+      expect(logMsg).toContain("syscall=spawn");
+    });
+  });
 });