Judge ADR 0326 §3 only where a definition is written (hq issue 574)

ParseManifest also reads stored builds again: a build's manifest at a
commit, the gate, a release, a module put back. betterbird's builds from
before its accounts file named its keys would have become uncomposable
there, so a send to g14 or shanks could fail and a rollback be refused.
The refusal now runs in module check, module add, a build taken in, the
builder and the merge gate's registration, and a file is no longer
reported by both §2 and §3.

cmd/mesh-controller/check.go

@@ -75,6 +75,16 @@ func moduleCheckFor(paths []string, longestMachine int, out io.Writer) error {
 			failed += len(wrong)
 			faulted[m.Module] = true
 		}
+		// A module that declares a setting names the keys of its mergeable files (novox/hq ADR 0326 §3,
+		// issue 574): judged where a definition is written, as at registration, never where a stored
+		// build is read again.
+		if wrong := catalogue.WrittenSettingsProblems(m); len(wrong) > 0 {
+			for _, p := range wrong {
+				fmt.Fprintf(out, "%s: %s\n", path, p)
+			}
+			failed += len(wrong)
+			faulted[m.Module] = true
+		}
 		if named := catalogue.InstallationProblems(m); len(named) > 0 {
 			for _, p := range named {
 				fmt.Fprintf(out, "%s: %s\n", path, p)

cmd/mesh-controller/modules.go

@@ -1051,6 +1051,11 @@ func namesNoInstallation(m catalogue.Manifest) error {
 	if problems := catalogue.TrustProblems(m); len(problems) > 0 {
 		return fmt.Errorf("%s", strings.Join(problems, "; "))
 	}
+	// And a module that declares a setting names the keys of its mergeable files (novox/hq ADR 0326
+	// §3, issue 574): judged where a definition is written, never where a stored build is read again.
+	if problems := catalogue.WrittenSettingsProblems(m); len(problems) > 0 {
+		return fmt.Errorf("%s", strings.Join(problems, "; "))
+	}
 	named := catalogue.InstallationProblems(m)
 	if len(named) == 0 {
 		return nil

cmd/mesh-controller/written_settings_test.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// ADR 0326 §3 is judged where a definition is written (novox/hq issue 574): `module check`, and
+// namesNoInstallation, which `module add`, a build taken in and the merge gate's registration run.
+func TestWhereADefinitionIsWrittenADeclaringModuleNamesItsFilesKeys(t *testing.T) {
+	const silent = `{"module":"mail-client","version":"1",
+		"settings":{"prefs":{"kind":"preference","default":"// none","why":"its own defaults until a machine names one"}},
+		"resources":[
+			{"id":"user-js","type":"file","path":"/var/lib/mail-client/user.js","mode":"0644","content":"${setting:prefs}\n"},
+			{"id":"accounts","type":"file","path":"/var/lib/mail-client/accounts.json","mode":"0600","merge":"json",
+			 "content":"{}\n"%s}]}`
+	dir := t.TempDir()
+	bad := filepath.Join(dir, "bad.json")
+	good := filepath.Join(dir, "good.json")
+	os.WriteFile(bad, []byte(strings.Replace(silent, "%s", "", 1)), 0o600)
+	os.WriteFile(good, []byte(strings.Replace(silent, "%s", `,"takes-settings":["accounts"]`, 1)), 0o600)
+
+	var out bytes.Buffer
+	if err := moduleCheck([]string{bad}, &out); err == nil ||
+		!strings.Contains(out.String(), "mergeable accounts names no takes-settings") {
+		t.Fatalf("module check passed a declaring module's silent mergeable file: %v\n%s", err, out.String())
+	}
+	out.Reset()
+	if err := moduleCheck([]string{good}, &out); err != nil {
+		t.Fatalf("the file naming its keys was refused: %v\n%s", err, out.String())
+	}
+
+	raw, _ := os.ReadFile(bad)
+	m, err := catalogue.ParseManifest(raw)
+	if err != nil {
+		t.Fatalf("reading it is not where it is judged: %v", err)
+	}
+	if err := namesNoInstallation(m); err == nil || !strings.Contains(err.Error(), "names no takes-settings") {
+		t.Fatalf("registration passed it: %v", err)
+	}
+}