Prove on a real bus that a merge of mesh-sdk changing only what its lib does not name leaves its tree input and new form unchanged (issue 1758, I9, ADR 0499 check 6 in miniature)

modules/mesh-delivery-indexer/cmd/mesh-delivery-indexer/integration_test.go

@@ -9,6 +9,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 	"time"
 
@@ -434,3 +435,46 @@ func TestIndexerGivesACandidateItsFingerprintWhenTheCheckerCreatesThePreviewsBuc
 		t.Errorf("none2 = %q within 5 s of the preview, want %q (computed from the preview)", got, delivery.ToolchainNoReport)
 	}
 }
+
+// TestAMergeOfMeshSDKChangingOnlyGoLeavesItsNamedTreeEqual: two merged messages of mesh-sdk (its module.json at 9cb4d59,
+// whose lib names its paths) differ in the root tree, as a change to go/ alone makes them, and carry the same objects of the
+// named paths; the module's kept tree, and so its fingerprint's tree input, is the same after both, and its new form
+// (fingerprint or reason) does not move (issue 1758, I9, ADR 0499 check clause 6 in miniature).
+func TestAMergeOfMeshSDKChangingOnlyGoLeavesItsNamedTreeEqual(t *testing.T) {
+	manifest, err := os.ReadFile("../../internal/index/testdata/sdk-9cb4d59-mesh-sdk.module.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	objects := map[string]string{"src": "1111111111111111111111111111111111111111", "test": "2222222222222222222222222222222222222222",
+		"package.json": "3333333333333333333333333333333333333333", "package-lock.json": "4444444444444444444444444444444444444444", "tsconfig.json": "5555555555555555555555555555555555555555"}
+	js, ctx, _, modules := startIndexer(t, func(context.Context, jetstream.KeyValue) {})
+	merged := func(merge, root string) delivery.Module {
+		data, err := delivery.EncodeForge(delivery.Forge{Kind: delivery.ForgeMerged, Repository: "novox/mesh-sdk", Branch: "feat/x", Number: 70,
+			Head: "0123456789abcdef0123456789abcdef01234567", Merge: merge, Root: root, Trees: map[string]string{"": root},
+			Manifests: map[string]string{"": string(manifest)}, Paths: map[string]map[string]string{"": objects}})
+		if err != nil {
+			t.Fatal(err)
+		}
+		if _, err := js.Publish(ctx, "mesh.stream.mesh-delivery-forge-bridge.event.forge.novox.mesh-sdk.merged", data); err != nil {
+			t.Fatal(err)
+		}
+		var m delivery.Module
+		for deadline := time.Now().Add(5 * time.Second); time.Now().Before(deadline); time.Sleep(50 * time.Millisecond) {
+			if e, err := modules.Get(ctx, "mesh-sdk"); err == nil {
+				if m, err = delivery.DecodeModule(e.Value()); err == nil && m.Commit == merge {
+					return m
+				}
+			}
+		}
+		t.Fatalf("modules.mesh-sdk = %+v within 5 s, want the merge %s", m, merge)
+		return m
+	}
+	first := merged("89abcdef0123456789abcdef0123456789abcdef", "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa")
+	second := merged("99abcdef0123456789abcdef0123456789abcdef", "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb")
+	if first.Inputs2 == nil || second.Inputs2 == nil || first.Inputs2.Tree != second.Inputs2.Tree || !strings.HasPrefix(first.Inputs2.Tree, delivery.NamedTreePrefix) {
+		t.Fatalf("kept trees %+v and %+v, want one named tree", first.Inputs2, second.Inputs2)
+	}
+	if first.FP2 != second.FP2 || first.None2 != second.None2 {
+		t.Errorf("the new form moved: %q/%q, then %q/%q", first.FP2, first.None2, second.FP2, second.None2)
+	}
+}