Fix the column set once, drop the unreachable separator override, and name the record predicate apart from the format table

cmd/fejkdata/main.go

@@ -225,8 +225,8 @@ var recordFormats = map[string]recordFormat{
 	"sql":  {line: func(r *fejkdata.Record, table string) string { return r.SQLInsert(table) }},
 }
 
-// recordFormat reports whether the format writes records rather than plain text.
+// writesRecords reports whether the format writes records rather than plain text.
-func (in invocation) recordFormat() bool {
+func (in invocation) writesRecords() bool {
 	return in.format != "text"
 }
 
@@ -248,7 +248,7 @@ func (in invocation) checkFlags() error {
 	if in.tableSet && in.format != "sql" {
 		return errors.New("--table names the INSERT target, so it needs --format sql")
 	}
-	if in.recordFormat() && in.separatorSet {
+	if in.writesRecords() && in.separatorSet {
 		return errors.New("--separator joins text values, so it has no effect with --format " + in.format)
 	}
 	return nil
@@ -298,10 +298,6 @@ func (in invocation) write(f *fejkdata.Generator, kind argKind, w io.Writer) err
 	if err != nil {
 		return err
 	}
-	separator := in.separator
-	if in.recordFormat() {
-		separator = "\n"
-	}
 	out := bufio.NewWriter(w)
 	for i := 0; i < in.repeat; i++ {
 		v, err := draw()
@@ -309,7 +305,7 @@ func (in invocation) write(f *fejkdata.Generator, kind argKind, w io.Writer) err
 			return err
 		}
 		if i > 0 {
-			out.WriteString(separator)
+			out.WriteString(in.separator)
 		}
 		out.WriteString(v)
 	}
@@ -320,7 +316,7 @@ func (in invocation) write(f *fejkdata.Generator, kind argKind, w io.Writer) err
 // draw builds what one render yields: the value's text, or the record's line in
 // the chosen format, the header carried ahead of the first one.
 func (in invocation) draw(f *fejkdata.Generator, kind argKind, arg string) (func() (string, error), error) {
-	if !in.recordFormat() {
+	if !in.writesRecords() {
 		if kind != argTemplate {
 			return func() (string, error) { return f.Fake(arg) }, nil
 		}

record.go

@@ -100,11 +100,11 @@ func (f *Generator) Record(path string) (*Record, error) {
 	if len(tail) > 0 {
 		return nil, fmt.Errorf("fejkdata: %s descends into %q, a field; only a category-level template is a record", path, tail[0])
 	}
-	t, err := recordOf(n)
+	t, columns, err := recordOf(n)
 	if err != nil {
 		return nil, fmt.Errorf("fejkdata: %s %w", path, err)
 	}
-	return renderRecord(f.rand, t), nil
+	return renderRecord(f.rand, t, columns), nil
 }
 
 // RecordTemplate is an inline record compiled, referenced and validated once,
@@ -112,13 +112,14 @@ func (f *Generator) Record(path string) (*Record, error) {
 type RecordTemplate struct {
 	g       *Generator
 	t       *template
+	columns []string
 }
 
 // Fake renders the record with one draw.
 func (t *RecordTemplate) Fake() *Record {
 	t.g.mu.Lock()
 	defer t.g.mu.Unlock()
-	return renderRecord(t.g.rand, t.t)
+	return renderRecord(t.g.rand, t.t, t.columns)
 }
 
 // NewRecordTemplate compiles an inline record — a JSON object with a format and
@@ -128,11 +129,11 @@ func (f *Generator) NewRecordTemplate(input string) (*RecordTemplate, error) {
 	if err != nil {
 		return nil, err
 	}
-	rt, err := recordOf(t.n)
+	tm, columns, err := recordOf(t.n)
 	if err != nil {
 		return nil, fmt.Errorf("fejkdata: an inline record %w", err)
 	}
-	return &RecordTemplate{g: f, t: rt}, nil
+	return &RecordTemplate{g: f, t: tm, columns: columns}, nil
 }
 
 // FakeRecord compiles and renders an inline record in one call.
@@ -144,32 +145,33 @@ func (f *Generator) FakeRecord(input string) (*Record, error) {
 	return t.Fake(), nil
 }
 
-// recordOf is the fence both record entry points pass: the node is a
+// recordOf is the fence both record entry points pass: the node is a template, it
-// category-level template, it carries no repeat — which composes the format
+// carries no repeat — which composes the format rather than projecting columns —
-// rather than projecting columns — and it offers at least one column.
+// and it offers at least one column. The columns come back with it, fixed for
-func recordOf(n node) (*template, error) {
+// every draw the caller goes on to make.
+func recordOf(n node) (*template, []string, error) {
 	t, ok := n.(*template)
 	if !ok {
-		return nil, errors.New("names a choice, not a template; only a category-level template is a record")
+		return nil, nil, errors.New("names a choice, not a template; a record is a template whose fields are its columns")
 	}
 	if t.repeat != 1 {
-		return nil, fmt.Errorf("carries repeat %d, which composes its format into one string; a record projects columns instead — drop the repeat and render the record again for more rows", t.repeat)
+		return nil, nil, fmt.Errorf("carries repeat %d, which composes its format into one string; a record projects columns instead — drop the repeat and render the record again for more rows", t.repeat)
 	}
-	if len(recordColumns(t)) == 0 {
+	columns := recordColumns(t)
-		return nil, errors.New("has no fields, so no columns")
+	if len(columns) == 0 {
+		return nil, nil, errors.New("has no fields, so no columns")
 	}
-	return t, nil
+	return t, columns, nil
 }
 
-// renderRecord projects a template's direct fields as columns, drawn once each,
+// renderRecord draws each column once, in the name order recordOf fixed. The
-// in name order. A {/path} binding is a render edge, not a column, so it is
+// columns share one reference scope, so two columns that reference one category
-// skipped the same way List and the graph do. The columns share one reference
+// read one draw of it.
-// scope, so two columns that reference one category read one draw of it.
+func renderRecord(s *session, t *template, columns []string) *Record {
-func renderRecord(s *session, t *template) *Record {
 	scope := &draws{variant: map[string]node{}, value: map[string]string{}}
-	r := &Record{}
+	r := &Record{columns: make([]Column, len(columns))}
-	for _, name := range recordColumns(t) {
+	for i, name := range columns {
-		r.columns = append(r.columns, Column{Name: name, Value: render(s, t.fields[name], scope)})
+		r.columns[i] = Column{Name: name, Value: render(s, t.fields[name], scope)}
 	}
 	return r
 }