New check: no placement directory and no manifest reading the indexer's placement, so the repository path cannot come back

checks/noplacement/go.mod

@@ -0,0 +1,3 @@
+module git.novox.be/novox/mesh-catalog/checks/noplacement
+
+go 1.22

checks/noplacement/main.go

@@ -0,0 +1,94 @@
+// Command noplacement refuses what the repository path of placement left behind (novox/hq ADR 0567 §1, §8, §10).
+//
+// Placement, which module runs on which node, is bus state held by the seat mesh-placement; no file of the
+// catalogue says it, and no manifest reads it from the delivery indexer, which no longer keeps it. It refuses:
+//
+//  1. a `placement` directory (or file) at the root of the catalogue;
+//
+//  2. a manifest naming a state, stream, event or bucket of the indexer's placement (`mesh-delivery-indexer.placement…`
+//     or `mesh-delivery-indexer_placement…`) in any string value, such as `reads`.
+//
+//     go run . <catalogue root>
+//
+// Exits 1 on a finding.
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+// Prefixes are the names of the indexer's placement parts; a manifest string starting with one names them.
+var Prefixes = []string{"mesh-delivery-indexer.placement", "mesh-delivery-indexer_placement"}
+
+// Findings is every refusal in the catalogue at root, sorted.
+func Findings(root string) ([]string, error) {
+	var out []string
+	if _, err := os.Lstat(filepath.Join(root, "placement")); err == nil {
+		out = append(out, "placement: the repository holds no placement; it is bus state of the seat mesh-placement (novox/hq ADR 0567 §1)")
+	}
+	manifests, err := filepath.Glob(filepath.Join(root, "modules", "*", "module.json"))
+	if err != nil {
+		return nil, err
+	}
+	sort.Strings(manifests)
+	for _, file := range manifests {
+		raw, err := os.ReadFile(file)
+		if err != nil {
+			return nil, err
+		}
+		var doc any
+		if err := json.Unmarshal(raw, &doc); err != nil {
+			return nil, fmt.Errorf("%s: %w", file, err)
+		}
+		module := filepath.Base(filepath.Dir(file))
+		for _, s := range named(doc, nil) {
+			out = append(out, fmt.Sprintf("%s: names %q, which the indexer no longer keeps; placement is the seat mesh-placement's (novox/hq ADR 0567 §8)", module, s))
+		}
+	}
+	return out, nil
+}
+
+// named collects the strings of a decoded manifest that start with one of the Prefixes.
+func named(v any, into []string) []string {
+	switch v := v.(type) {
+	case string:
+		for _, p := range Prefixes {
+			if strings.HasPrefix(v, p) {
+				return append(into, v)
+			}
+		}
+	case []any:
+		for _, e := range v {
+			into = named(e, into)
+		}
+	case map[string]any:
+		for _, e := range v {
+			into = named(e, into)
+		}
+	}
+	return into
+}
+
+func main() {
+	if len(os.Args) != 2 {
+		fmt.Fprintln(os.Stderr, "usage: noplacement <catalogue root>")
+		os.Exit(2)
+	}
+	found, err := Findings(os.Args[1])
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	for _, f := range found {
+		fmt.Println(f)
+	}
+	if len(found) > 0 {
+		os.Exit(1)
+	}
+	fmt.Println("no placement directory, and no manifest reads the indexer's placement")
+}

checks/noplacement/main_test.go

@@ -0,0 +1,54 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func TestFindingsRefuseWhatThePlacementPathLeft(t *testing.T) {
+	for _, row := range []struct {
+		name  string
+		files map[string]string
+		want  string // empty: clean
+	}{
+		{"clean", map[string]string{"modules/a/module.json": `{"module":"a","reads":["mesh-controller.assignments"]}`}, ""},
+		{"a placement directory", map[string]string{"placement/ace.json": `{}`}, "placement: the repository holds no placement"},
+		{"a read of the indexer's placement", map[string]string{"modules/a/module.json": `{"module":"a","reads":["mesh-delivery-indexer.placement"]}`}, `a: names "mesh-delivery-indexer.placement"`},
+		{"a read of its candidates", map[string]string{"modules/b/module.json": `{"module":"b","reads":["mesh-delivery-indexer.placement-candidates"]}`}, "placement-candidates"},
+		{"its event", map[string]string{"modules/c/module.json": `{"module":"c","on":[{"event":"mesh-delivery-indexer.placement-changed"}]}`}, "placement-changed"},
+		{"the seat's own state is allowed", map[string]string{"modules/d/module.json": `{"module":"d","reads":["mesh-placement.placement"]}`}, ""},
+	} {
+		t.Run(row.name, func(t *testing.T) {
+			root := t.TempDir()
+			for path, text := range row.files {
+				p := filepath.Join(root, path)
+				if err := os.MkdirAll(filepath.Dir(p), 0o755); err != nil {
+					t.Fatal(err)
+				}
+				if err := os.WriteFile(p, []byte(text), 0o644); err != nil {
+					t.Fatal(err)
+				}
+			}
+			got, err := Findings(root)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if all := strings.Join(got, "\n"); (row.want == "") != (all == "") || !strings.Contains(all, row.want) {
+				t.Fatalf("findings = %q, want one containing %q", all, row.want)
+			}
+		})
+	}
+}
+
+// The script's run of this check over the real tree (novox/hq ADR 0529 clause 2).
+func TestTheCatalogueHoldsNoPlacementOfTheRepositoryPath(t *testing.T) {
+	got, err := Findings(filepath.Join("..", ".."))
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, f := range got {
+		t.Error(f)
+	}
+}

checks/noplacement/reads-outside

@@ -0,0 +1,6 @@
+# What these tests read outside their package, as paths from the repository's root (a glob, or a directory read whole;
+# ? before a path whose absence is read). mesh-build-go hashes them into the package's digest, so its verdict is kept
+# until one of them changes (issue 1936). An empty list, or a line matching nothing, keeps nothing.
+# the root, for a placement directory, and every manifest, for a read of the indexer's placement states.
+?placement
+modules/*/module.json