internal/pkg: improve error resolution

This was taking way too long for early failures.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/pkg_test.go

@@ -15,6 +15,7 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"strconv"
 	"syscall"
 	"testing"
 	"unique"
@@ -1137,6 +1138,40 @@ func TestDependencyCureError(t *testing.T) {
 	}
 }
 
+// earlyFailureF is a [FloodArtifact] with a large dependency graph resulting in
+// a large [DependencyCureError].
+type earlyFailureF int
+
+func (earlyFailureF) Kind() pkg.Kind       { return pkg.KindExec }
+func (earlyFailureF) Params(*pkg.IContext) {}
+func (earlyFailureF) IsExclusive() bool    { return false }
+
+func (a earlyFailureF) Dependencies() []pkg.Artifact {
+	deps := make([]pkg.Artifact, a)
+	for i := range deps {
+		deps[i] = a - 1
+	}
+	return deps
+}
+
+func (a earlyFailureF) Cure(*pkg.FContext) error {
+	if a != 0 {
+		panic("unexpected cure on " + strconv.Itoa(int(a)))
+	}
+	return stub.UniqueError(0xcafe)
+}
+
+func TestDependencyCureErrorEarly(t *testing.T) {
+	checkWithCache(t, []cacheTestCase{
+		{"early", nil, func(t *testing.T, _ *check.Absolute, c *pkg.Cache) {
+			_, _, err := c.Cure(earlyFailureF(8))
+			if !errors.Is(err, stub.UniqueError(0xcafe)) {
+				t.Fatalf("Cure: error = %v", err)
+			}
+		}, pkg.MustDecode("E4vEZKhCcL2gPZ2Tt59FS3lDng-d_2SKa2i5G_RbDfwGn6EemptFaGLPUDiOa94C")},
+	})
+}
+
 func TestNew(t *testing.T) {
 	t.Parallel()