From 4089d75df0450ae43ffea62e750faf74fdac6d8c Mon Sep 17 00:00:00 2001
From: Peng Cheng <e1143754@u.nus.edu>
Date: Sun, 11 Oct 2026 10:50:12 +0800
Subject: [PATCH] fix(macos): follow the log by name in dev-run.sh --log

The app recreates ~/Library/Logs/LCTMac.log with
FileManager.createFile(atPath:contents:) in applicationDidFinishLaunching,
which replaces the file with a new inode. That usually happens after
dev-run.sh has already started `tail -f`, so tail kept following the
old, deleted file and --log never showed the new run's lines. Use
`tail -F`, which reopens the path when the file is replaced.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 macos/Scripts/dev-run.sh                  |  7 +++++--
 macos/Tests/LCTMacTests/DevRunTests.swift | 16 ++++++++++++++++
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/macos/Scripts/dev-run.sh b/macos/Scripts/dev-run.sh
index 1caaf2e..8f8d771 100755
--- a/macos/Scripts/dev-run.sh
+++ b/macos/Scripts/dev-run.sh
@@ -13,7 +13,7 @@
 #
 # Usage: Scripts/dev-run.sh [--no-launch] [--log]
 #   --no-launch   build & sign only, do not start the app
-#   --log         after launching, tail -f ~/Library/Logs/LCTMac.log
+#   --log         after launching, tail -F ~/Library/Logs/LCTMac.log
 
 set -euo pipefail
 
@@ -162,7 +162,10 @@ if [ "$LAUNCH" -eq 1 ]; then
     echo "dev-run.sh: launched $APP_BUNDLE"
     if [ "$TAIL_LOG" -eq 1 ]; then
         echo "dev-run.sh: tailing $LOG_FILE (Ctrl-C to stop)"
-        tail -f "$LOG_FILE"
+        # -F, not -f: the app replaces the log file (new inode) when it
+        # finishes launching, which is usually after tail has started, and
+        # `tail -f` would keep following the old, deleted file.
+        tail -F "$LOG_FILE"
     fi
 else
     echo "dev-run.sh: build complete (--no-launch): $APP_BUNDLE"
diff --git a/macos/Tests/LCTMacTests/DevRunTests.swift b/macos/Tests/LCTMacTests/DevRunTests.swift
index 97a0f41..90e12f3 100644
--- a/macos/Tests/LCTMacTests/DevRunTests.swift
+++ b/macos/Tests/LCTMacTests/DevRunTests.swift
@@ -288,6 +288,22 @@ final class DevRunTests: XCTestCase {
         XCTAssertFalse(log.contains("open "), "--no-launch must not open the app, got: \(log)")
     }
 
+    func testDevRun_Log_FollowsLogFileByName() throws {
+        let stubs = try makeStubbedRun(securityOutput: nil)
+        try writeExecutable("tail", contents: """
+            #!/bin/bash
+            echo "tail $*" >> "$LCT_STUB_LOG"
+            """, in: stubs.workDir.appendingPathComponent("bin"))
+        let result = try run("dev-run.sh", arguments: ["--log"], stubs: stubs, identity: "DEADBEEFDEADBEEFDEADBEEFDEADBEEFDEADBEEF")
+
+        XCTAssertEqual(result.exitStatus, 0, "dev-run.sh failed: \(result.stderr)")
+        let log = stubLog(stubs)
+        XCTAssertTrue(
+            log.contains("tail -F ") && log.contains("Library/Logs/LCTMac.log"),
+            "the app replaces its log file on launch, so --log must follow it by name (tail -F), got: \(log)"
+        )
+    }
+
     func testDevRun_RunningInstance_QuitsGracefullyWithoutPkill() throws {
         let pgrep = """
             #!/bin/bash