Nucleic: Gitea Runner macOS VM Support

Sources/gitea-macos-runner/Main.swift

@@ -137,24 +137,50 @@ final class ProgressPrinter: @unchecked Sendable {
     private let lock = NSLock()
     private var lastLine = ""
 
+    /// Whether carriage-return rewriting means anything here.
+    ///
+    /// Piped to a file or captured by `launchd`, `\r` produces one unreadable
+    /// mega-line, so each update becomes its own line instead. `FileHandle`
+    /// writes go straight to the descriptor either way — there is no buffer to
+    /// flush, which is what makes a stall attributable to the stage last
+    /// printed rather than to output sitting unwritten.
+    private let isInteractive = isatty(fileno(stderr)) == 1
+
     /// Rewrites the current line.
     func update(_ line: String) {
         lock.lock()
         defer { lock.unlock() }
         guard line != lastLine else { return }
         lastLine = line
+        guard isInteractive else {
+            FileHandle.standardError.write(Data((line + "\n").utf8))
+            return
+        }
         let padding = String(repeating: " ", count: max(0, 78 - line.count))
         FileHandle.standardError.write(Data(("\r" + line + padding).utf8))
     }
 
+    /// Emits a standalone line without losing the status line under it.
+    func line(_ text: String) {
+        lock.lock()
+        let carried = lastLine
+        lock.unlock()
+
+        finish(text)
+        if !carried.isEmpty {
+            update(carried)
+        }
+    }
+
     /// Ends the line so subsequent output starts cleanly.
     func finish(_ line: String? = nil) {
         lock.lock()
         defer { lock.unlock() }
         if let line {
-            let padding = String(repeating: " ", count: max(0, 78 - line.count))
-            FileHandle.standardError.write(Data(("\r" + line + padding + "\n").utf8))
-        } else if !lastLine.isEmpty {
+            let padding = isInteractive ? String(repeating: " ", count: max(0, 78 - line.count)) : ""
+            let prefix = isInteractive ? "\r" : ""
+            FileHandle.standardError.write(Data((prefix + line + padding + "\n").utf8))
+        } else if !lastLine.isEmpty, isInteractive {
             FileHandle.standardError.write(Data("\n".utf8))
         }
         lastLine = ""