Invalidate downstream results when stages are replaced

internal/app/run_control.go

@@ -3,6 +3,7 @@ package app
 import (
 	"context"
 	"fmt"
+	"strings"
 	"time"
 
 	"gitea.maximumdirect.net/eric/narratio/internal/artifacts"
@@ -23,22 +24,40 @@ type stageDecision struct {
 	Action stageAction
 }
 
+const (
+	staleReasonForcedReplacement = "upstream stage was force-run"
+	staleReasonChangedResult     = "upstream stage result changed"
+	staleReasonFailure           = "upstream stage failed"
+	staleReasonSelfSkip          = "upstream stage self-skipped"
+	staleReasonNotResumable      = "upstream stage result was not resumable"
+)
+
+type priorStageOutcome struct {
+	exists     bool
+	status     manifest.StageStatus
+	skipReason string
+	outputs    int
+}
+
 func decideStageActions(stages []stage.Stage, m *manifest.Manifest, force bool) []stageDecision {
 	out := make([]stageDecision, 0, len(stages))
 	for _, s := range stages {
-		action := stageActionRun
-		// TODO: incorporate stale detection once checksum/input change tracking is implemented.
-		if !force && stageSucceeded(m, s.Name()) {
-			action = stageActionSkip
-		}
 		out = append(out, stageDecision{
 			Stage:  s,
-			Action: action,
+			Action: decideStageAction(s, m, force),
 		})
 	}
 	return out
 }
 
+func decideStageAction(s stage.Stage, m *manifest.Manifest, force bool) stageAction {
+	// TODO: incorporate stale detection once checksum/input change tracking is implemented.
+	if !force && stageSucceeded(m, s.Name()) {
+		return stageActionSkip
+	}
+	return stageActionRun
+}
+
 func stageSucceeded(m *manifest.Manifest, name string) bool {
 	if m == nil || m.Stages == nil {
 		return false
@@ -47,6 +66,29 @@ func stageSucceeded(m *manifest.Manifest, name string) bool {
 	return sr != nil && sr.Status == manifest.StatusSucceeded
 }
 
+func capturePriorStageOutcome(m *manifest.Manifest, name string) priorStageOutcome {
+	if m == nil || m.Stages == nil || m.Stages[name] == nil {
+		return priorStageOutcome{}
+	}
+	record := m.Stages[name]
+	outcome := priorStageOutcome{
+		exists:  true,
+		status:  record.Status,
+		outputs: len(record.Outputs),
+	}
+	if record.Error != nil && record.Error.Code == "skipped" {
+		outcome.skipReason = record.Error.Message
+	}
+	return outcome
+}
+
+func (o priorStageOutcome) isSameSelfSkip(reason string) bool {
+	return o.exists &&
+		o.status == manifest.StatusSkipped &&
+		o.outputs == 0 &&
+		o.skipReason == strings.TrimSpace(reason)
+}
+
 func loadManifestIfPresent(ctx context.Context, cfg *config.Config) (*manifest.Manifest, error) {
 	path := artifacts.SessionManifestPathForCampaign(
 		cfg.Pipeline.Workspace.Root,
@@ -91,10 +133,6 @@ func downstreamStageNames(stageName string) []string {
 	return nil
 }
 
-func invalidateDownstreamSucceededStages(m *manifest.Manifest, upstreamStage string, at time.Time) []string {
-	return invalidateDownstreamSucceededStagesWithReason(m, upstreamStage, at, "upstream stage rerun with force")
-}
-
 func invalidateDownstreamSucceededStagesWithReason(m *manifest.Manifest, upstreamStage string, at time.Time, reason string) []string {
 	if m == nil || m.Stages == nil {
 		return nil