fix(context_for_task): ask each file's sensitivity once per call (live packs lost their affected tests)

CHANGELOG.md

@@ -300,6 +300,14 @@
 
 ### Fixed
 
+- **`context_for_task` asks each file's sensitivity once per call, so live packs
+  keep their affected tests.** The walk asks whether every node it reaches is in a
+  sensitive file, 600 to 2,000 times per pack over a hundred or two files, and
+  the daemon answers each by resolving the path's project on disk. A live pack
+  overran its 2 s graph deadline even on a warm index, losing the affected-tests
+  section and its run-first line in three of five real tasks. The answer is now
+  remembered per path for the call.
+
 - **An edit to the global `config.toml` made while the daemon starts is no
   longer missed.** The daemon loads the file, then starts watching it; a write
   in between raised no event the watch could see, so the daemon kept the older

internal/tools/context_collect.go

@@ -6,6 +6,7 @@ import (
 	"path"
 	"path/filepath"
 	"strings"
+	"sync"
 	"time"
 )
 
@@ -330,11 +331,30 @@ func (c *ContextCollector) walk(ctx, graphCtx context.Context, pack *contextPack
 
 // sensitiveFor adapts the injected decision to the index's root-relative paths.
 // It is nil when no decision is wired, which withholds nothing.
+//
+// The answer is remembered per path for the one call: a walk asks about every
+// node it reaches, 600 to 2,000 times over a hundred or two files, and the
+// daemon's decision resolves the path's project each time (workspace detection
+// on disk), which made a live pack overrun its graph deadline. A path's
+// sensitivity cannot change within the call that asks. Only the walk's asks go
+// through this memo; the constraint, document and hint paths ask c.sensitive
+// directly, a few times each.
 func (c *ContextCollector) sensitiveFor(ctx context.Context, root string) func(string) bool {
 	if c.sensitive == nil {
 		return nil
 	}
-	return func(rel string) bool { return c.sensitive(ctx, absUnder(root, rel), "") }
+	var mu sync.Mutex
+	seen := map[string]bool{}
+	return func(rel string) bool {
+		mu.Lock()
+		defer mu.Unlock()
+		if v, ok := seen[rel]; ok {
+			return v
+		}
+		v := c.sensitive(ctx, absUnder(root, rel), "")
+		seen[rel] = v
+		return v
+	}
 }
 
 // markStale marks the relationships that come from a file whose bytes changed

internal/tools/context_sensitive_memo_test.go

@@ -0,0 +1,70 @@
+package tools
+
+import (
+	"context"
+	"path/filepath"
+	"strings"
+	"sync"
+	"testing"
+)
+
+// TestContextForTask_AsksEachPathItsSensitivityOnce: a walk reaches many nodes of
+// the same files, and the daemon's decision resolves the path's project on disk
+// each time it is asked, so one call asks it once per path. The withheld control
+// shows the remembered answer is still the decision's own: every node of the
+// sensitive file is withheld, the repeated asks included, and none of its text
+// reaches the pack.
+func TestContextForTask_AsksEachPathItsSensitivityOnce(t *testing.T) {
+	s := newShop(t)
+	var mu sync.Mutex
+	asked := map[string]int{}
+	s.collector.WithSensitive(func(_ context.Context, p, _ string) bool {
+		mu.Lock()
+		asked[p]++
+		mu.Unlock()
+		return strings.HasSuffix(filepath.ToSlash(p), "/cart/cart.go")
+	})
+	pack := s.collect(t, map[string]any{"symbols": []string{"pricing/discount.go#Apply"}, "intent": contextIntentChange})
+
+	if len(asked) == 0 {
+		t.Fatal("control: the walk never asked about sensitivity, so the test proves nothing")
+	}
+	for p, n := range asked {
+		if n != 1 {
+			t.Errorf("%s was asked %d times in one call, want once", p, n)
+		}
+	}
+	// Every node from the sensitive file is withheld, not only the first one asked
+	// about: a memo that remembered the wrong answer would leak the later ones.
+	var fromCart int
+	for _, r := range pack.Related {
+		if r.Node.Path != "cart/cart.go" {
+			continue
+		}
+		fromCart++
+		if !r.Withheld {
+			t.Errorf("%s from the sensitive cart/cart.go is not withheld: %+v", nodeSelector(r.Node), r)
+		}
+	}
+	if fromCart < 2 {
+		t.Fatalf("control: the walk reached %d node(s) of cart/cart.go, want at least 2, so a repeated answer is tested", fromCart)
+	}
+	out := renderContextPack(pack)
+	for _, body := range []string{"kept := c.items[:0]", "sub += it.Cents * it.Qty", "c.items[i].Qty += it.Qty"} {
+		if strings.Contains(out, body) {
+			t.Errorf("content of the sensitive cart/cart.go reached the pack: %q", body)
+		}
+	}
+
+	// A second call asks again: the memory lasts one call, never across calls.
+	before := len(asked)
+	_ = s.collect(t, map[string]any{"symbols": []string{"pricing/discount.go#Apply"}, "intent": contextIntentChange})
+	for p, n := range asked {
+		if n != 2 {
+			t.Errorf("%s was asked %d times over two calls, want twice (once per call)", p, n)
+		}
+	}
+	if len(asked) != before {
+		t.Errorf("the second call reached %d paths, the first %d: the walk is not deterministic", len(asked), before)
+	}
+}