Build the walk root in New, drop the categories copy, and correct the node and renders comments

drawfence_test.go

@@ -28,7 +28,7 @@ func fenceRoots(t *testing.T, f *Generator) ([]fenceRoot, map[string]*table) {
 	t.Helper()
 	var roots []fenceRoot
 	tables := map[string]*table{}
-	_ = walkNodes(f.categories, func(path string, n node) error {
+	_ = walkNodes(f.root.children, func(path string, n node) error {
 		switch n := n.(type) {
 		case *template:
 			roots = append(roots, fenceRoot{path, n})
@@ -61,7 +61,7 @@ func TestReplayPairsFindsWhatAWholeReplayFinds(t *testing.T) {
 	if err != nil {
 		t.Fatalf("New() = %v", err)
 	}
-	_ = walkNodes(shipped.categories, func(path string, n node) error {
+	_ = walkNodes(shipped.root.children, func(path string, n node) error {
 		if tm, ok := n.(*template); ok {
 			roots = append(roots, fenceRoot{path, tm})
 		}
@@ -85,7 +85,7 @@ func TestReplayPairsFindsWhatAWholeReplayOfSelectedRowsFinds(t *testing.T) {
 		t.Fatalf("New = %v", err)
 	}
 	var reads []pathRead
-	_ = walkNodes(f.categories, func(_ string, n node) error {
+	_ = walkNodes(f.root.children, func(_ string, n node) error {
 		tb, isTable := n.(*table)
 		if !isTable || tb.keyIndex < 0 || tb.familyRoot().path != "region" {
 			return nil

fejkdata.go

@@ -31,12 +31,11 @@ var ErrNoData = errors.New("no data: WithoutShippedData needs at least one WithD
 // from one goroutine. The compiled tree is immutable after [New], so List, NewTemplate
 // and NewRecordTemplate read it without a lock; mu guards the rest, which every render takes.
 type Generator struct {
-	mu         sync.Mutex
-	rand       *session
-	categories map[string]node
-	root       folder // the categories as the node a path walks from, owned here so a walk allocates none
-	records    map[node]recordShape
-	structs    map[reflect.Type]structResult
+	mu      sync.Mutex
+	rand    *session
+	root    folder // the categories as the node a path walks from, owned here so a walk allocates none
+	records map[node]recordShape
+	structs map[reflect.Type]structResult
 }
 
 // session is one generator's mutable render state: the seeded rng plus the {seq()}
@@ -112,7 +111,7 @@ func New(opts ...Option) (*Generator, error) {
 	if err != nil {
 		return nil, fmt.Errorf("fejkdata: %w", err)
 	}
-	return &Generator{rand: rng, categories: cats}, nil
+	return &Generator{rand: rng, root: folder{children: cats}}, nil
 }
 
 // List returns the sorted dotted paths Fake renders: each category and every field,
@@ -120,8 +119,8 @@ func New(opts ...Option) (*Generator, error) {
 // segment, so a path continues through one only where every variant carries it.
 func (f *Generator) List() []string {
 	var out []string
-	for _, name := range sortedNames(f.categories) {
-		for _, p := range paths(f.categories[name]) {
+	for _, name := range sortedNames(f.root.children) {
+		for _, p := range paths(f.root.children[name]) {
 			out = append(out, join(name, p))
 		}
 	}

holdfence.go

@@ -152,9 +152,8 @@ func isFixed(n node) bool {
 }
 
 // renders reports whether rendering n can reach anything in want, following the
-// same edges expand does. seen keeps a node shared by several routes from being
-// walked twice; checkNoCycles has already proved the graph is a DAG, so the walk
-// ends.
+// same edges expand does. seen keeps a node from being walked twice, so the walk
+// ends across a cycle too.
 func renders(n node, want, seen map[node]bool) bool {
 	if want[n] {
 		return true

inline.go

@@ -32,7 +32,7 @@ func (f *Generator) NewTemplate(input string) (*Template, error) {
 	if err != nil {
 		return nil, fmt.Errorf("fejkdata: %w", err)
 	}
-	if err := inlineBinding(n, "template", f.categories).bind(); err != nil {
+	if err := inlineBinding(n, "template", f.root.children).bind(); err != nil {
 		return nil, fmt.Errorf("fejkdata: %w", err)
 	}
 	return &Template{g: f, n: n}, nil

node.go

@@ -11,7 +11,7 @@ import (
 
 // node is a compiled element of the namespace tree: a folder, choice, null,
 // template, table, column or row. Compiling JSON into these once (see compile)
-// means rendering never re-inspects the raw JSON or re-sums weights. A new kind needs a
+// means rendering never re-inspects the raw JSON. A new kind needs a
 // case in contained, paths, render and renderEdges; each panics on a kind it does not list.
 type node interface{ isNode() }
 

path_test.go

@@ -50,7 +50,7 @@ func TestDeepDottedPath(t *testing.T) {
 	// A 5-segment path descends through alternating object/array nodes; choices
 	// on the path are single-variant, so it resolves deterministically.
 	f := engine(1)
-	f.categories = map[string]node{
+	f.root.children = map[string]node{
 		"deep": compiled(t, `{"format":"{a}","a":{"format":"{b}","b":{"format":"{c}","c":{"format":"{d}","d":"leaf"}}}}`),
 	}
 	if got, err := f.Fake("deep.a.b.c.d"); err != nil || got != "leaf" {
@@ -64,7 +64,7 @@ func TestDeepDottedPath(t *testing.T) {
 
 func TestDescendIntoStringErrors(t *testing.T) {
 	f := engine(1)
-	f.categories = map[string]node{"greeting": compiled(t, `"hej"`)}
+	f.root.children = map[string]node{"greeting": compiled(t, `"hej"`)}
 	if _, err := f.Fake("greeting.extra"); err == nil || !strings.Contains(err.Error(), `no field "extra"`) {
 		t.Fatalf("Fake(greeting.extra) = %v, want a no-field error", err)
 	}
@@ -153,7 +153,7 @@ func TestBindingKeyIsNotAPathSegment(t *testing.T) {
 
 func TestFakePathNavigation(t *testing.T) {
 	f := engine(1)
-	f.categories = map[string]node{
+	f.root.children = map[string]node{
 		"addr": compiled(t, `{"format":"{street}","street":"Main"}`),
 	}
 	if got, err := f.Fake("addr"); err != nil || !strings.Contains(got, "Main") {

record.go

@@ -126,7 +126,7 @@ func (f *Generator) FakeRecord(path string) (*Record, error) {
 	if err != nil {
 		return nil, fmt.Errorf("fejkdata: %w", err)
 	}
-	_, n, tail, err := resolveCategory(f.categories, segments)
+	_, n, tail, err := resolveCategory(f.root.children, segments)
 	if err != nil {
 		return nil, fmt.Errorf("fejkdata: %s: %w", path, err)
 	}

render.go

@@ -25,7 +25,6 @@ func (f *Generator) Fake(path string) (string, error) {
 	}
 	var set holdSet
 	sc := renderScope{set: &set}
-	f.root.children = f.categories
 	n, err := descend(f.rand, &f.root, segments, sc)
 	if err != nil {
 		return "", fmt.Errorf("fejkdata: %s: %w", path, err)

shape_test.go

@@ -61,8 +61,8 @@ func shippedShape(f *Generator) string {
 			}
 		}
 	}
-	for _, name := range sortedNames(f.categories) {
-		walk(name, f.categories[name])
+	for _, name := range sortedNames(f.root.children) {
+		walk(name, f.root.children[name])
 	}
 	var b strings.Builder
 	for _, p := range f.List() {

struct.go

@@ -49,7 +49,7 @@ func (f *Generator) structShapeOf(t reflect.Type) (*structShape, error) {
 	if label == "" {
 		label = "struct"
 	}
-	sc := &structCompile{categories: f.categories, visiting: map[reflect.Type]bool{}, structsLeft: maxStructs}
+	sc := &structCompile{categories: f.root.children, visiting: map[reflect.Type]bool{}, structsLeft: maxStructs}
 	shape, err := sc.compileShape(t, label)
 	if err == nil && shape.empty() {
 		err = fmt.Errorf("%s has no fake tags, so nothing to fill", t)

table_test.go

@@ -991,7 +991,7 @@ func TestEnteredRowsAgreeWithPinning(t *testing.T) {
 	f := newGenerator(t, writeFiles(t, geo()), WithSeed(1))
 	var tables []*table
 	for _, category := range []string{"region", "municipality", "locality"} {
-		tbl, isTable := f.categories[category].(*table)
+		tbl, isTable := f.root.children[category].(*table)
 		if !isTable {
 			t.Fatalf("%s is not a table", category)
 		}
@@ -1063,7 +1063,7 @@ func TestProbeReportsTheTablesADrawPins(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-		head := f.categories[segs[0]].(*table)
+		head := f.root.children[segs[0]].(*table)
 		probe := &pathProbe{drawn: map[*table]bool{}}
 		if _, err := probe.walk(head, segs[1:]); err != nil {
 			t.Fatalf("%s: %v", path, err)

todo.md

@@ -26,10 +26,6 @@ least modify.
 
 This round, in order:
 
-- Correct the false comments: `node` says rendering never re-sums weights, which
-  `builtLookup` does on first draw; `Generator` claims immutable after `New`, while
-  `Fake` sets `root.children` each call, which belongs in `New`; `renders` credits
-  `checkNoCycles`, which an inline binding never runs.
 - Run the nine-seat panel again and file what it names here.
 
 ### Data