Join 9: the builder reads the build seats' steps in seat form, at the seat's holder (A-116, A-128)

module.json reads seat:node-build-<language>.steps as the checker and the watchman do; the
tools bundle reads <holder>.steps, the holder found by seatlist.HolderOf where it is read.

Builds: design 47 G A-116, A-126, A-128

Claude-Session: https://claude.ai/code/session_01NcbgfGKaxw984XyAPfLm4h

modules/mesh-delivery-builder/cmd/mesh-delivery-builder-tools/build_test.go

@@ -2,9 +2,12 @@ package main
 
 import (
 	"encoding/json"
+	"errors"
 	"strings"
 	"testing"
 
+	"mesh-delivery-builder/internal/build"
+
 	"git.novox.be/novox/mesh-delivery/contracts/go/clients/meshcatalogclient"
 	"git.novox.be/novox/mesh-delivery/contracts/go/seats/meshcatalog"
 )
@@ -30,3 +33,24 @@ func TestNewestIsReadFromTheCatalogHalfOfEachWatchedBranch(t *testing.T) {
 		t.Fatalf("newest = %v, %v, want each branch's entry fingerprint whole", got, err)
 	}
 }
+
+// A build seat's steps are read in its holder's state, the holder found where it is read (design 47 G A-128); a seat with no
+// holder found reads as an error.
+func TestABuildSeatsStepsAreReadInItsHoldersState(t *testing.T) {
+	var named []string
+	steps := stepsOfHolder(func(seat string) (string, error) {
+		if seat == "node-build-go" {
+			return "mesh-build-go", nil
+		}
+		return "", errors.New("no holder")
+	}, func(name string) build.StateRead {
+		named = append(named, name)
+		return build.StateRead{Keys: func() ([]string, error) { return []string{"k"}, nil }}
+	})
+	if ks, err := steps("node-build-go").Keys(); err != nil || len(ks) != 1 || len(named) != 1 || named[0] != "mesh-build-go.steps" {
+		t.Errorf("read %v (keys %v, %v); want the holder's mesh-build-go.steps", named, ks, err)
+	}
+	if _, err := steps("node-build-node").Keys(); err == nil || !strings.Contains(err.Error(), "node-build-node") {
+		t.Errorf("a seat with no holder reads %v; want an error naming it", err)
+	}
+}

modules/mesh-delivery-builder/cmd/mesh-delivery-builder-tools/main.go

@@ -293,6 +293,22 @@ func askKept(s stdio.KeptState, state, bucket, what string, bound time.Duration,
 	}
 }
 
+// stepsOfHolder reads a build seat's steps in the state of the seat's holder (`<holder>.steps`), the holder found where it is
+// read by mesh-sdk's seatlist helper (design 47 G A-128, A-126), as the manifest's `seat:<seat>.steps` reads name it; a seat
+// whose holder cannot be found reads as an error naming it.
+func stepsOfHolder(holder func(seat string) (string, error), read func(name string) build.StateRead) func(seat string) build.StateRead {
+	return func(seat string) build.StateRead {
+		module, err := holder(seat)
+		if err != nil {
+			fail := fmt.Errorf("the holder of %s is not found: %w", seat, err)
+			return build.StateRead{Keys: func() ([]string, error) { return nil, fail },
+				Get:     func(string) (json.RawMessage, time.Time, error) { return nil, time.Time{}, fail },
+				Written: func(string) time.Time { return time.Time{} }}
+		}
+		return read(module + ".steps")
+	}
+}
+
 func read(s stdio.KeptState) build.StateRead {
 	return build.StateRead{Keys: s.Keys, Get: func(key string) (json.RawMessage, time.Time, error) {
 		e, err := s.Get(key)
@@ -331,7 +347,7 @@ const (
 
 func main() {
 	reasks := stdio.State(build.ReAsksState)
-	r := build.StuckReader{Logf: func(f string, a ...any) { fmt.Fprintf(os.Stderr, "[mesh-delivery-builder-tools] "+f+"\n", a...) }, Builds: read(stdio.State("builds")), ReAsks: read(reasks), StepsOf: func(seat string) build.StateRead { return read(stdio.State(seat + ".steps")) },
+	r := build.StuckReader{Logf: func(f string, a ...any) { fmt.Fprintf(os.Stderr, "[mesh-delivery-builder-tools] "+f+"\n", a...) }, Builds: read(stdio.State("builds")), ReAsks: read(reasks), StepsOf: stepsOfHolder(func(seat string) (string, error) { return seatlist.HolderOf(stdio.Ask, seat) }, func(name string) build.StateRead { return read(stdio.State(name)) }),
 		Hearing: read(stdio.State(buildrun.HearingState))}
 	put := func(key string, value []byte) error {
 		_, err := reasks.Put(key, json.RawMessage(value))

modules/mesh-delivery-builder/cmd/mesh-delivery-builder/names_test.go

@@ -26,7 +26,7 @@ func TestTheNamesAreTheManifests(t *testing.T) {
 		t.Fatal(err)
 	}
 	for _, read := range []string{
-		"node-build-go.steps", "node-build-image.steps", "node-build-node.steps",
+		"seat:node-build-go.steps", "seat:node-build-image.steps", "seat:node-build-node.steps",
 	} {
 		if !slices.Contains(m.Reads, read) {
 			t.Errorf("the builder reads %s, its manifest's reads are %v", read, m.Reads)

modules/mesh-delivery-builder/manifest_test.go

@@ -119,8 +119,9 @@ func TestManifestDeclarations(t *testing.T) { // 1607/AC1
 	// 1887/A4c: the builder chooses no node, so it reads neither presence nor have, invokes no build module's tool and
 	// holds no capacity; it puts asks on the three build seats and reads their steps (ADR 0525 §1, §4, §5). Whether a
 	// node's machine is heard it asks the watchdogs seat's presence (issue 1966, ADR 0596 §2, ADR 0668 §3).
-	if want := []string{"node-build-go.steps", "node-build-image.steps", "node-build-node.steps",
-		"seat:mesh-module-assigner.assignments"}; !reflect.DeepEqual(sorted(m.Reads), want) {
+	// Each build seat's steps are read in seat form, its holder found where it is read (A-116, A-128).
+	if want := []string{"seat:mesh-module-assigner.assignments", "seat:node-build-go.steps", "seat:node-build-image.steps",
+		"seat:node-build-node.steps"}; !reflect.DeepEqual(sorted(m.Reads), want) {
 		t.Errorf("reads = %v, want %v", m.Reads, want)
 	}
 	if want := []string{"node-build-go", "node-build-image", "node-build-node", "operator-channel"}; !reflect.DeepEqual(sorted(m.Uses), want) {

modules/mesh-delivery-builder/module.json

@@ -155,10 +155,10 @@
     { "name": "build-log", "max-age-days": 30, "max-mib": 3072 }
   ],
   "reads": [
-    "node-build-go.steps",
-    "node-build-image.steps",
-    "node-build-node.steps",
-    "seat:mesh-module-assigner.assignments"
+    "seat:mesh-module-assigner.assignments",
+    "seat:node-build-go.steps",
+    "seat:node-build-image.steps",
+    "seat:node-build-node.steps"
   ],
   "uses": [
     "node-build-go",