parallelized installs

taskctx.go

@@ -0,0 +1,102 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+// Goroutine-local task output routing.
+//
+// Why: install handlers in custom.go and post.go are deeply nested calls
+// that use fmt.Printf/Println directly and pass CmdOpts to runCmd. To route
+// their output into a per-task buffer (so parallel workers don't interleave
+// on os.Stdout), we'd otherwise need to thread an io.Writer through every
+// signature — ~30 call sites of churn including tests.
+//
+// Instead we keep a sync.Map keyed by goroutine id. The parallel orchestrator
+// associates a taskOutput with its worker goroutine before invoking the
+// handler; helpers below check the map and route output to the active task
+// when present, falling back to direct stdout otherwise. Sequential callers
+// observe no behavior change.
+//
+// goid() uses runtime.Stack — a small hack, but stable and idiomatic for
+// goroutine-local state where context.Context threading would dwarf the
+// surrounding work.
+
+var activeTaskByGoroutine sync.Map // map[uint64]*taskOutput
+
+func goid() uint64 {
+	var buf [64]byte
+	n := runtime.Stack(buf[:], false)
+	s := string(buf[:n])
+	s = strings.TrimPrefix(s, "goroutine ")
+	end := strings.IndexByte(s, ' ')
+	if end < 0 {
+		return 0
+	}
+	id, _ := strconv.ParseUint(s[:end], 10, 64)
+	return id
+}
+
+// withTaskOutput pins tOut to the current goroutine for the duration of fn,
+// then unpins. Re-entrant calls overwrite the previous binding and restore
+// it on return. A nil tOut is treated as "no binding" (sequential mode).
+func withTaskOutput(tOut *taskOutput, fn func()) {
+	if tOut == nil {
+		fn()
+		return
+	}
+	id := goid()
+	prev, hadPrev := activeTaskByGoroutine.Load(id)
+	activeTaskByGoroutine.Store(id, tOut)
+	defer func() {
+		if hadPrev {
+			activeTaskByGoroutine.Store(id, prev)
+		} else {
+			activeTaskByGoroutine.Delete(id)
+		}
+	}()
+	fn()
+}
+
+// currentTask returns the taskOutput pinned to the current goroutine, or
+// nil if none. Cheap enough to call per print (~microseconds).
+func currentTask() *taskOutput {
+	v, ok := activeTaskByGoroutine.Load(goid())
+	if !ok {
+		return nil
+	}
+	return v.(*taskOutput)
+}
+
+// taskPrintf routes via the active task (if any) or directly to stdout.
+func taskPrintf(format string, args ...any) {
+	if t := currentTask(); t != nil {
+		t.Printf(format, args...)
+		return
+	}
+	fmt.Printf(format, args...)
+}
+
+// taskPrintln routes via the active task (if any) or directly to stdout.
+func taskPrintln(args ...any) {
+	if t := currentTask(); t != nil {
+		t.Println(args...)
+		return
+	}
+	fmt.Println(args...)
+}
+
+// taskOut returns the io.Writer that runCmd / runShell should target via
+// CmdOpts.Out for the active task. Returns nil when there is no active task,
+// which preserves runCmd's default streamed-to-stdout behavior.
+func taskOut() io.Writer {
+	if t := currentTask(); t != nil {
+		return t.Writer()
+	}
+	return nil
+}