Give the inline pipeline its own file, and record the shape, padding and template-API decisions

README.md

@@ -25,12 +25,13 @@ fejkdata '{"format":"name: {x}","x":["bosse","lina"]}'  # name: bosse or name: l
 
 A path names a category, or a field inside one: each dot segment descends one
 level — folders, then the category (a JSON file), then fields. An argument that is
-a JSON object or array, or that carries a `{` token, is instead an **inline
-template**: a format string or a JSON value compiled and rendered on the spot. Its
-tokens reach the data by reference from the root — `{/sv_SE.person.last}` (or
-`{.name}`, which means the same here), so shipped and `--data-path` categories are
-available — and `{..name}` is rejected, an inline template having no folder to step
-up from. A path never contains a brace, so the two cannot collide (see
+a JSON object, array or string, or that carries a `{` token, is instead an
+**inline template**: a format string or a JSON value compiled and rendered on the
+spot. Its tokens reach the data by reference from the root —
+`{/sv_SE.person.last}`, so shipped and `--data-path` categories are alike
+available. An inline template sits in no folder, so the folder-relative `{.name}`
+and `{..name}` are rejected naming the root spelling. A path never contains a
+brace, a bracket or a quote, so the two cannot collide (see
 [Decisions](#decisions)).
 
 | Flag | |
@@ -46,7 +47,9 @@ up from. A path never contains a brace, so the two cannot collide (see
 `--name value` and `--name=value` both work, a short flag's value attaches or
 follows (`-n3`, `-n 3`) and short flags bundle (`-hn 3`) — see
 [Decisions](#decisions); flags go anywhere, `--` ends them. Exit codes: `0` success, `1` runtime error (missing
-dir, unknown path), `2` misuse. From a checkout: `go run ./cmd/fejkdata …`.
+dir, unknown path), `2` misuse — a bad flag, an argument that names neither a
+template nor a path, or an inline template that does not compile. From a checkout:
+`go run ./cmd/fejkdata …`.
 
 ### Your own data
 
@@ -107,8 +110,8 @@ work with no data on disk. A directory is a namespace: each JSON file is a
 category named after the file, each subdirectory a dot-path segment, so
 `mydata/sv_SE/person.json` is `sv_SE.person` and replaces the shipped one.
 Sources merge in order; matching folders combine, any other clash is won by the
-last loaded. Names may not use `.`, `|`, `(`, `{`, `}`, `[`, `]` or `/`; dot-prefixed
-entries are skipped, so a data directory can also be a checkout.
+last loaded. Names may not use `.`, `|`, `(`, `{`, `}`, `[`, `]`, `"` or `/`;
+dot-prefixed entries are skipped, so a data directory can also be a checkout.
 
 Each locale carries `address`, `color`, `company`, `date`, `email`, `ip`,
 `person`, `phone`, `price`, `sentence`, `ssn`, `time`, `url`, `username`,
@@ -346,8 +349,9 @@ tokens add cost in proportion to the output.
 2. **Text means what it says** — a format renders as written; only `{…}` varies,
    random characters included (`{digits(3)}`). One spelling per result; the wrong
    one is a load error naming the right one.
-3. **Every mistake is a load error** — `New` rejects; `Fake` on a loaded generator
-   fails only for an unknown path.
+3. **Every mistake is a load error** — `New` rejects the data and `NewTemplate`
+   the inline template; on a loaded generator `Fake` fails only for an unknown
+   path, and `Template.Fake` cannot fail at all.
 4. **Zero to a value in one command** — `go install`, then `fejkdata sv_SE.person`:
    no checkout, no flag. Flags are GNU-form (`--seed 42`, `-n 3`) in any position;
    the first custom template needs no escape and no option.
@@ -372,13 +376,24 @@ tokens add cost in proportion to the output.
   naming the double-dash spelling, and `-s=42` is rejected naming both short
   spellings: `=` belongs to the long form, and reading `=42` as the value would
   make `-d=./x` a directory named `=./x`.
-- **An argument is a template by its shape, not by a flag.** A JSON object or
-  array, or a string carrying a `{` token, is an inline template; anything else is
-  a path. A name may not contain a brace or a bracket, so a path can never collide
-  with either spelling, and the `[` of a JSON array is gated on valid JSON so a
-  stray copied bracket never swallows an argument. No `--template` flag is needed.
-  Reserving both brackets — though only a leading `[` could collide — keeps one
-  simple name rule instead of a leading-position special case.
+- **An argument is a template by its shape, not by a flag.** A JSON object, array
+  or string, or a string carrying a `{` token, is an inline template; anything else
+  is a path. A name may not contain a brace, a bracket or a quote, so a path can
+  never collide with any of those spellings, and the leading `[` or `"` is gated on
+  valid JSON so a stray copied bracket never swallows an argument — it names
+  nothing, and says so. No `--template` flag is needed. Reserving the characters
+  whole — though only a leading one could collide — keeps one simple name rule
+  instead of a leading-position special case. The JSON string is what makes the
+  library's own advice reachable: the error for an object holding only a format
+  names `"…"`, and that spelling has to work where it is printed.
+- **A padded JSON argument is rejected, not trimmed.** Padding is the one place the
+  two readings disagree — a format string renders it, JSON drops it — so the
+  spelling that renders is named rather than silently chosen.
+- **`FakeTemplate` and `NewTemplate` both stay.** They reach the same value but not
+  at the same cost: `NewTemplate` pays the compile and validation once and renders
+  many times, `FakeTemplate` is the one-shot call, and `--repeat` is exactly the
+  case that needs the first. The pair is `regexp.MustCompile` and `regexp.Match`,
+  not two spellings of one result.
 - **The shipped data is embedded, not discovered.** A directory a machine happens
   to have would make `--seed 42` machine-dependent. Data still lives in `data/`
   as JSON; `--data-path` layers over it.
@@ -467,6 +482,7 @@ fejkdata.go     Generator, New, options, the embedded data set, List
 node.go         the node model and JSON -> node compilation
 path.go         the dotted-path walk, and proving a path resolves
 render.go       Fake and the recursive renderer (choices, format strings, expansions)
+inline.go       inline templates: Template, NewTemplate, FakeTemplate, and their compile and link
 template.go     the {token} grammar: scanning, tokens, operands, validation, compiling a format
 hold.go         the hold: one draw per expansion for paths and operands, and its fences
 reference.go    reference sigils, and binding references across the tree

cmd/fejkdata/main.go

@@ -27,11 +27,11 @@ const usage = `Usage: fejkdata [flags] <path|template>
   <template>             a format string or JSON value to render inline, e.g.
                          'name: {/sv_SE.person.last}' or '{"format":"{x}","x":["bosse","lina"]}'
 
-An argument containing a { token, or a JSON object or array, is a template; any
-other argument is a path (a path never contains a brace). Templates reach the data
-with a reference: {/sv_SE.person.first} from the root, whether the data is shipped
-or layered with --data-path. A [ that is not valid JSON names no template and no
-path.
+An argument containing a { token, or a JSON object, array or string, is a
+template; any other argument is a path (a path never contains a brace, a bracket
+or a quote). Templates reach the data by reference from the root —
+{/sv_SE.person.first} — whether the data is shipped or layered with --data-path. A
+bracket that is not valid JSON names no template and no path.
 
   -d, --data-path D      a data directory to layer over the shipped data (repeatable; last wins on a clash)
   -h, --help             print this help, then exit
@@ -195,18 +195,22 @@ func parseArgs(argv []string) (invocation, error) {
 	return in, nil
 }
 
-// check rejects a flag combination that cannot run.
-func (in invocation) check() error {
+// check rejects a flag combination or an argument that cannot run, and reports
+// what the argument names, so its shape is settled before any data is read.
+func (in invocation) check() (argKind, error) {
 	if in.list && len(in.paths) > 0 {
-		return errors.New("--list takes no path")
+		return argPath, errors.New("--list takes no path")
 	}
 	if in.list && (in.repeatSet || in.separatorSet) {
-		return errors.New("--list takes no --repeat or --separator")
+		return argPath, errors.New("--list takes no --repeat or --separator")
 	}
-	if !in.list && len(in.paths) != 1 {
-		return fmt.Errorf("expected one path, got %d", len(in.paths))
+	if in.list {
+		return argPath, nil
 	}
-	return nil
+	if len(in.paths) != 1 {
+		return argPath, fmt.Errorf("expected one path, got %d", len(in.paths))
+	}
+	return classify(in.paths[0])
 }
 
 func (in invocation) options() []fejkdata.Option {
@@ -223,24 +227,19 @@ func (in invocation) options() []fejkdata.Option {
 	return opts
 }
 
-// write streams the path's renders to w, repeat of them joined by the separator
-// and ended by a newline. A path that renders once renders every time, so a Fake
-// failure comes before anything is written; a write failure surfaces from Flush,
-// bufio keeping the first one.
-func (in invocation) write(f *fejkdata.Generator, w io.Writer) error {
+// write streams the argument's renders to w, repeat of them joined by the
+// separator and ended by a newline. A value that renders once renders every time,
+// so a render failure comes before anything is written; a write failure surfaces
+// from Flush, bufio keeping the first one.
+func (in invocation) write(f *fejkdata.Generator, kind argKind, w io.Writer) error {
 	arg := in.paths[0]
-	var draw func() (string, error)
-	switch {
-	case isTemplate(arg):
+	draw := func() (string, error) { return f.Fake(arg) }
+	if kind == argTemplate {
 		t, err := f.NewTemplate(arg)
 		if err != nil {
 			return templateError{err}
 		}
 		draw = func() (string, error) { return t.Fake(), nil }
-	case strings.HasPrefix(arg, "["):
-		return templateError{fmt.Errorf("%q starts with [ but is not valid JSON, so it names no template and no path", arg)}
-	default:
-		draw = func() (string, error) { return f.Fake(arg) }
 	}
 	out := bufio.NewWriter(w)
 	for i := 0; i < in.repeat; i++ {
@@ -264,16 +263,30 @@ type templateError struct{ error }
 
 func (e templateError) Unwrap() error { return e.error }
 
-// isTemplate reports whether an argument is an inline template rather than a
-// path: a format string carrying a { token, or a JSON object or array. A name may
-// not contain a brace or bracket, so both spellings collide with no path; the [
-// gate is valid-JSON so a [ alone never swallows an argument that merely began
-// with a copied bracket.
-func isTemplate(arg string) bool {
-	if strings.ContainsRune(arg, '{') {
-		return true
+type argKind int
+
+const (
+	argPath argKind = iota
+	argTemplate
+)
+
+// classify reads what a positional argument names by its shape: a format string
+// carrying a { token, or a JSON object, array or string, is an inline template;
+// anything else is a path. A name may hold neither a brace nor a bracket nor a
+// quote, so no path collides with any of those spellings, and the JSON gate is
+// valid-JSON so a copied bracket names nothing rather than swallowing an argument.
+func classify(arg string) (argKind, error) {
+	if strings.ContainsRune(arg, '{') || (isJSONStart(arg) && json.Valid([]byte(arg))) {
+		return argTemplate, nil
 	}
-	return strings.HasPrefix(arg, "[") && json.Valid([]byte(arg))
+	if i := strings.IndexAny(arg, "[]"); i >= 0 {
+		return argPath, fmt.Errorf("%q holds a %q, which no path may, and it is not valid JSON, so it names no template either", arg, arg[i:i+1])
+	}
+	return argPath, nil
+}
+
+func isJSONStart(arg string) bool {
+	return strings.HasPrefix(arg, "[") || strings.HasPrefix(arg, `"`)
 }
 
 func main() { os.Exit(run(os.Args[1:], os.Stdout, os.Stderr)) }
@@ -292,7 +305,8 @@ func run(args []string, stdout, stderr io.Writer) int {
 		fmt.Fprintln(stdout, "fejkdata "+buildVersion())
 		return 0
 	}
-	if err := in.check(); err != nil {
+	kind, err := in.check()
+	if err != nil {
 		return misuse(stderr, err)
 	}
 	f, err := fejkdata.New(in.options()...)
@@ -309,7 +323,7 @@ func run(args []string, stdout, stderr io.Writer) int {
 		}
 		return 0
 	}
-	if err := in.write(f, stdout); err != nil {
+	if err := in.write(f, kind, stdout); err != nil {
 		var te templateError
 		if errors.As(err, &te) {
 			return misuse(stderr, te.error)
@@ -321,7 +335,8 @@ func run(args []string, stdout, stderr io.Writer) int {
 }
 
 func misuse(stderr io.Writer, err error) int {
-	fmt.Fprintf(stderr, "fejkdata: %v\ntry 'fejkdata --help'\n", err)
+	// A library error already names the program, so the prefix is not doubled.
+	fmt.Fprintf(stderr, "fejkdata: %s\ntry 'fejkdata --help'\n", strings.TrimPrefix(err.Error(), "fejkdata: "))
 	return 2
 }
 

cmd/fejkdata/main_test.go

@@ -301,21 +301,34 @@ func TestRunShippedDataByDefault(t *testing.T) {
 	}
 }
 
-func TestIsTemplate(t *testing.T) {
-	for arg, want := range map[string]bool{
-		"sv_SE.person":   false,
-		"person.last":    false,
-		"[abc]":          false, // a [ that is not valid JSON is not a template
-		"[abc].field":    false,
-		"name: {x}":      true, // a { token: a path can never carry a brace
-		`{"format":"x"}`: true,
-		`["a","b"]`:      true, // a JSON array carries no brace
-		`[1, 2]`:         true,
+func TestClassify(t *testing.T) {
+	for arg, want := range map[string]argKind{
+		"sv_SE.person":   argPath,
+		"person.last":    argPath,
+		`"abc`:           argPath,     // a quote opening no JSON string is part of a name
+		"name: {x}":      argTemplate, // a { token: a path can never carry a brace
+		`{"format":"x"}`: argTemplate,
+		`["a","b"]`:      argTemplate, // a JSON array carries no brace
+		`[1, 2]`:         argTemplate,
+		`"hello"`:        argTemplate, // a JSON string, the spelling a format-only object names
 	} {
-		if got := isTemplate(arg); got != want {
-			t.Errorf("isTemplate(%q) = %v, want %v", arg, got, want)
+		got, err := classify(arg)
+		if err != nil || got != want {
+			t.Errorf("classify(%q) = %v, %v; want %v", arg, got, err, want)
 		}
 	}
+	for _, arg := range []string{"[abc]", "[abc].field", "x[1]", "a]b"} {
+		if _, err := classify(arg); err == nil {
+			t.Errorf("classify(%q) = no error; want the bracket rejected", arg)
+		}
+	}
+}
+
+func TestRunShapeMisuseBeforeLoad(t *testing.T) {
+	code, _, errb := runOut("--no-shipped-data", "[abc]")
+	if code != 2 || !strings.Contains(errb, "[abc]") || strings.Contains(errb, "--data-path") {
+		t.Fatalf("shape misuse with no data = %d, %q; want the shape error before any load", code, errb)
+	}
 }
 
 func TestRunInlineTemplate(t *testing.T) {
@@ -327,6 +340,10 @@ func TestRunInlineTemplate(t *testing.T) {
 	if code != 0 || (out != "name: bosse\n" && out != "name: lina\n") {
 		t.Fatalf("inline JSON template = %d, %q, want one name, stderr %q", code, out, errb)
 	}
+	code, out, errb = runOut("--seed", "1", `"name: {/sv_SE.person.last}"`)
+	if code != 0 || !strings.HasPrefix(out, "name: ") || strings.Contains(out, "{") {
+		t.Fatalf("inline JSON string = %d, %q, stderr %q", code, out, errb)
+	}
 	code, out, errb = runOut("--seed", "1", "-n", "2", `{digits(1)}`)
 	if code != 0 || len(strings.Split(strings.TrimRight(out, "\n"), "\n")) != 2 {
 		t.Fatalf("inline template with --repeat = %d, %q, stderr %q", code, out, errb)
@@ -339,11 +356,15 @@ func TestRunTemplateMisuse(t *testing.T) {
 		"[red,green]",     // a near-miss JSON array (unquoted strings)
 		`{"format":"x"}`,  // an object holding only a format
 		"{/no.such.path}", // a reference into nothing
+		"x[1]",            // a bracket no path may hold
 	} {
 		code, out, errb := runOut("--seed", "1", arg)
 		if code != 2 || out != "" || !strings.Contains(errb, "try 'fejkdata --help'") {
 			t.Errorf("run(%q) = %d, %q, %q; want misuse naming --help", arg, code, out, errb)
 		}
+		if strings.Contains(errb, "fejkdata: fejkdata:") {
+			t.Errorf("run(%q) doubled the program prefix: %q", arg, errb)
+		}
 	}
 }
 

data.go

@@ -62,19 +62,13 @@ func loadData(sources []dataSource) (map[string]node, error) {
 	if len(root) == 0 {
 		return nil, fmt.Errorf("no .json data found")
 	}
-	// The fences here and the scoped ones [Generator.NewTemplate] runs are one
-	// sequence split across two entry points; a new fence lands a twin below and
-	// in NewTemplate (see its comment for the one omission, checkNoCycles).
 	if err := linkRefs(root); err != nil {
 		return nil, err
 	}
 	if err := checkNoCycles(root); err != nil {
 		return nil, err
 	}
-	if err := checkRepeatReach(root); err != nil {
-		return nil, err
-	}
-	if err := checkBoundLevelsHeld(root); err != nil {
+	if err := checkScope(treeScope(root)); err != nil {
 		return nil, err
 	}
 	return root, nil

graph.go

@@ -165,24 +165,28 @@ func pathLeaves(n node, tail []string) []node {
 	return out
 }
 
-// checkRepeatReach bounds the renders a repeat multiplies to along any root-to-leaf
-// path, so nested repeats cannot build what one repeat may not. It runs after
-// checkNoCycles, whose guarantee is what lets the walk terminate.
-func checkRepeatReach(root map[string]node) error {
-	mem := reachMemo{}
-	return walkNodes(root, func(path string, n node) error {
-		return repeatCheck(path, n, mem)
-	})
+// nodeScope is the set of nodes one validation pass covers: a whole loaded tree,
+// or a single inline node.
+type nodeScope func(fn func(path string, n node) error) error
+
+func treeScope(root map[string]node) nodeScope {
+	return func(fn func(path string, n node) error) error { return walkNodes(root, fn) }
 }
 
-// checkNodeRepeatReach is checkRepeatReach for one inline node: each template in
-// it is bounded, following reference edges into the already-validated tree the same
-// way a repeat through a reference multiplies along a path.
-func checkNodeRepeatReach(n node) error {
+func inlineScope(n node) nodeScope {
+	return func(fn func(path string, m node) error) error { return eachNode(n, "template", fn) }
+}
+
+// checkScope runs the per-node fences over a scope, each over the whole scope
+// before the next, so which of several broken nodes is reported does not depend on
+// the walk. It runs after checkNoCycles, whose guarantee is what lets the walks
+// terminate.
+func checkScope(s nodeScope) error {
 	mem := reachMemo{}
-	return eachNode(n, "template", func(path string, m node) error {
-		return repeatCheck(path, m, mem)
-	})
+	if err := s(func(path string, n node) error { return repeatCheck(path, n, mem) }); err != nil {
+		return err
+	}
+	return s(heldCheck)
 }
 
 type reachMemo map[node]int
@@ -204,6 +208,8 @@ func (m reachMemo) of(n node) int {
 	return r
 }
 
+// repeatCheck bounds the renders a repeat multiplies to along any root-to-leaf
+// path, so nested repeats cannot build what one repeat may not.
 func repeatCheck(path string, n node, mem reachMemo) error {
 	if t, ok := n.(*template); ok && t.repeat > 1 && mem.of(n) > MaxRepeat {
 		return fmt.Errorf("%s: repeat %d multiplies to %d renders along one path, above the maximum %d", path, t.repeat, mem.of(n), MaxRepeat)

hold.go

@@ -6,27 +6,11 @@ import (
 	"strings"
 )
 
-// checkBoundLevelsHeld rejects every route to a held name except the ones that read
-// its draw. An expansion holds one draw of that name; anything else that renders it
-// draws again, and the two disagree. checkNoOverlap settles the spellings within one
+// heldCheck rejects every route to a held name except the ones that read its draw.
+// An expansion holds one draw of that name; anything else that renders it draws
+// again, and the two disagree. checkNoOverlap settles the spellings within one
 // format (a token, an operand); this settles the rest — a reference, whether it
 // sits in that format or in anything the format renders, however deep.
-//
-// It runs after checkNoCycles, whose guarantee is what lets the walk terminate.
-func checkBoundLevelsHeld(root map[string]node) error {
-	return walkNodes(root, func(path string, n node) error {
-		return heldCheck(path, n)
-	})
-}
-
-// checkNodeBoundLevelsHeld is checkBoundLevelsHeld for one inline node: the same
-// held fence, over its own templates and the shared tree they reference.
-func checkNodeBoundLevelsHeld(n node) error {
-	return eachNode(n, "template", func(path string, m node) error {
-		return heldCheck(path, m)
-	})
-}
-
 func heldCheck(path string, n node) error {
 	t, ok := n.(*template)
 	if !ok || len(t.held) == 0 {

inline.go

@@ -0,0 +1,97 @@
+package fejkdata
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+// Template is an inline template compiled, referenced and validated against a
+// generator's loaded data once, ready to render many times with [Template.Fake].
+// It is safe for concurrent use: Fake serializes on its generator's lock, so a
+// seeded sequence is reproducible only when a generator — and its templates — are
+// drawn from one goroutine.
+type Template struct {
+	g *Generator
+	n node
+}
+
+// Fake renders the template with one draw.
+func (t *Template) Fake() string {
+	t.g.mu.Lock()
+	defer t.g.mu.Unlock()
+	return render(t.g.rand, t.n)
+}
+
+// NewTemplate compiles an inline template — a format string or a JSON value — and
+// binds its references against the loaded tree, so repeated renders pay the
+// compile and validation once. It shares [New]'s guarantees: a bad template errors
+// here, and rendering cannot fail.
+//
+// checkNoCycles is the one fence loadData runs that an inline node does not need:
+// the loaded tree is proven acyclic at [New], the node is a finite tree, and no
+// tree node can reference it, so nothing it renders can reach itself.
+func (f *Generator) NewTemplate(input string) (*Template, error) {
+	n, err := compileInput(input)
+	if err != nil {
+		return nil, fmt.Errorf("fejkdata: %w", err)
+	}
+	if err := linkNodeRefs(n, f.categories); err != nil {
+		return nil, fmt.Errorf("fejkdata: %w", err)
+	}
+	if err := checkScope(inlineScope(n)); err != nil {
+		return nil, fmt.Errorf("fejkdata: %w", err)
+	}
+	return &Template{g: f, n: n}, nil
+}
+
+// FakeTemplate compiles and renders an inline template in one call. It is
+// [NewTemplate] then [Template.Fake]; to render the same template many times, hold
+// the *Template and call its Fake.
+func (f *Generator) FakeTemplate(input string) (string, error) {
+	t, err := f.NewTemplate(input)
+	if err != nil {
+		return "", err
+	}
+	return t.Fake(), nil
+}
+
+// compileInput compiles an inline template: a JSON value, or a bare format string
+// when the input is not JSON. A JSON string literal and a bare string compile
+// alike (both are a template with no fields); the other JSON scalars — a number,
+// bool or null — are no template, so they are rejected here, as a data file that
+// was one would be at load. Padding is where the two readings would disagree — a
+// format string renders it, JSON drops it — so a padded JSON value is rejected
+// naming the one that renders.
+func compileInput(input string) (node, error) {
+	var raw any
+	if err := json.Unmarshal([]byte(input), &raw); err != nil {
+		return compile(input)
+	}
+	if trimmed := strings.TrimSpace(input); trimmed != input {
+		return nil, fmt.Errorf("a JSON template may not be padded with spaces, which a format string would render; write %s", trimmed)
+	}
+	return compile(raw)
+}
+
+// linkNodeRefs binds the references in an inline node's templates against the
+// loaded tree. An inline template sits in no folder, so . and .. name nothing and
+// are rejected for the root spelling they would otherwise silently mean.
+func linkNodeRefs(n node, root map[string]node) error {
+	return eachNode(n, "template", func(path string, m node) error {
+		t, ok := m.(*template)
+		if !ok {
+			return nil
+		}
+		for _, name := range refTokens(t.format) {
+			sigil, rest, err := refShape(name)
+			if err != nil {
+				return fmt.Errorf("%s: reference {%s}: %w", path, name, err)
+			}
+			if sigil != "/" {
+				return fmt.Errorf("%s: reference {%s}: an inline template has no folder; write {/%s}", path, name, rest)
+			}
+		}
+		return linkTemplateRefs(nil, path, t, root)
+	})
+}

inline_test.go

@@ -94,7 +94,7 @@ func TestFakeTemplateErrors(t *testing.T) {
 		{`"{x}"`, `no field "x"`},
 		{`"{digits(0)}"`, "must be positive"},
 		{`name: {/no.such.path}`, "no entry"},
-		{`name: {..nope}`, "no folder above"},
+		{`name: {..nope}`, "write {/nope}"},
 		{`{"format":"x"}`, "is a string"},
 		{`{/misc.country} {/misc.country.alpha2}`, "renders a level"},
 	} {
@@ -105,6 +105,23 @@ func TestFakeTemplateErrors(t *testing.T) {
 	}
 }
 
+func TestFakeTemplateJSONString(t *testing.T) {
+	f := shipped(t)
+	got := tmpl(t, f, `"name: {/sv_SE.person.last}"`)
+	if !strings.HasPrefix(got, "name: ") || strings.Contains(got, "{") {
+		t.Fatalf("FakeTemplate(JSON string) = %q, want a rendered last name after the prefix", got)
+	}
+}
+
+func TestPaddedJSONIsRejected(t *testing.T) {
+	f := shipped(t)
+	in := `{"format":"{x}","x":["a","b"]}`
+	_, err := f.NewTemplate("  " + in + "  ")
+	if err == nil || !strings.Contains(err.Error(), "write "+in) {
+		t.Fatalf("NewTemplate(padded JSON) = %v, want an error naming the unpadded spelling", err)
+	}
+}
+
 func TestNewTemplateReusable(t *testing.T) {
 	f := shipped(t)
 	tmpl, err := f.NewTemplate(`{digits(2)}`)

loading_test.go

@@ -275,8 +275,6 @@ func TestNewErrors(t *testing.T) {
 			map[string]string{"a|b": `"1"`},
 			`category "a|b" contains "|"`,
 		},
-		// A bracket is not a token-grammar character, but the CLI reads an argument
-		// starting with [ as a JSON array, so a name carrying one would be misread.
 		"field name with a bracket": {
 			map[string]string{"a": `{"format":"{x}","x":"1","b[c":"2"}`},
 			`field "b[c" contains "["`,
@@ -285,6 +283,10 @@ func TestNewErrors(t *testing.T) {
 			map[string]string{"[abc]": `"1"`},
 			`category "[abc]" contains "["`,
 		},
+		"field name with a quote": {
+			map[string]string{"a": `{"format":"{x}","x":"1","b\"c":"2"}`},
+			`field "b\"c" contains "\""`,
+		},
 		// An empty name is not a path segment, so List never offered it — while a
 		// bare {}, a trailing dot in Fake("a.") and a {/a.} reference all reached
 		// it. The engine accepted spellings it would never advertise.

node.go

@@ -136,19 +136,6 @@ func (t *template) compileFormat() error {
 	return checkNoRepeatedRead(t.format, c, t.refs)
 }
 
-// compileInput compiles an inline template: a JSON value, or a bare format string
-// when the input is not JSON. A JSON string literal and a bare string compile
-// alike (both are a template with no fields); the other JSON scalars — a number,
-// bool or null — are no template, so they are rejected here, as a data file that
-// was one would be at load.
-func compileInput(input string) (node, error) {
-	var raw any
-	if err := json.Unmarshal([]byte(input), &raw); err != nil {
-		return compile(input)
-	}
-	return compile(raw)
-}
-
 func compileChoice(items []any) (node, error) {
 	if len(items) == 0 {
 		return nil, fmt.Errorf("empty choice")
@@ -350,15 +337,15 @@ func weightOf(raw any) (float64, error) {
 
 // reservedInName is what a category, folder or field name may not contain: a dot
 // separates the segments of a path, '|' the arms of a token, '(' opens a function
-// call, braces delimit the token, '/' starts a reference, and a bracket would be
-// misread by the command line as a JSON array. A name carrying one is rejected
-// where it is authored rather than where it would be unreachable.
-const reservedInName = ".|({}/[]"
+// call, braces delimit the token, '/' starts a reference, and brackets and a quote
+// open a JSON value. A name carrying one is rejected where it is authored rather
+// than where it would be unreachable.
+const reservedInName = ".|({}/[]\""
 
 // reservedList spells reservedInName for an error message, so the two cannot drift.
 var reservedList = strings.Join(strings.Split(reservedInName, ""), " ")
 
-// checkName rejects a name the dot path, {token} and CLI grammars cannot spell.
+// checkName rejects a name the dot path, {token} and JSON grammars cannot spell.
 // Both a category or folder and a field go through it, so there is one answer to
 // what a name may contain.
 func checkName(name string) error {
@@ -366,7 +353,7 @@ func checkName(name string) error {
 		return fmt.Errorf("%q is empty, which is not a path segment, so List never offers it", name)
 	}
 	if i := strings.IndexAny(name, reservedInName); i >= 0 {
-		return fmt.Errorf("%q contains %q; a name may not use %s, which the dot path, {token} and CLI grammars reserve",
+		return fmt.Errorf("%q contains %q; a name may not use %s, which the dot path, {token} and JSON grammars reserve",
 			name, name[i:i+1], reservedList)
 	}
 	return nil

one_spelling_test.go

@@ -47,3 +47,13 @@ func TestInertObjectIsRejected(t *testing.T) {
 		}
 	}
 }
+
+func TestInlineFolderSigilsAreRejected(t *testing.T) {
+	f := shipped(t)
+	for _, input := range []string{"{.sv_SE.person.last}", "{..sv_SE.person.last}"} {
+		_, err := f.NewTemplate(input)
+		if err == nil || !strings.Contains(err.Error(), "write {/sv_SE.person.last}") {
+			t.Errorf("NewTemplate(%q) = %v, want an error naming the root spelling", input, err)
+		}
+	}
+}

reference.go

@@ -110,19 +110,6 @@ func linkTemplateRefs(folder []string, path string, t *template, root map[string
 	return nil
 }
 
-// linkNodeRefs binds the references in an inline node's templates against the
-// loaded tree. The node has no folder of its own, so every sigil is root-relative:
-// / and . mean the root, .. has no folder above it.
-func linkNodeRefs(n node, root map[string]node) error {
-	return eachNode(n, "template", func(path string, m node) error {
-		t, ok := m.(*template)
-		if !ok {
-			return nil
-		}
-		return linkTemplateRefs(nil, path, t, root)
-	})
-}
-
 // eachTemplate calls fn once per template, with the folder its category sits in
 // and the dot path reaching it, folders and names in sorted order.
 func eachTemplate(root map[string]node, fn func(folder []string, path string, t *template) error) error {

render.go

@@ -30,59 +30,6 @@ func (f *Generator) Fake(path string) (string, error) {
 	return render(f.rand, n), nil
 }
 
-// Template is an inline template compiled, referenced and validated against a
-// generator's loaded data once, ready to render many times with [Template.Fake].
-// It is safe for concurrent use: Fake serializes on its generator's lock, so a
-// seeded sequence is reproducible only when a generator — and its templates — are
-// drawn from one goroutine.
-type Template struct {
-	g *Generator
-	n node
-}
-
-// Fake renders the template with one draw.
-func (t *Template) Fake() string {
-	t.g.mu.Lock()
-	defer t.g.mu.Unlock()
-	return render(t.g.rand, t.n)
-}
-
-// NewTemplate compiles an inline template — a format string or a JSON value — and
-// binds its references against the loaded tree, so repeated renders pay the
-// compile and validation once. It shares [New]'s guarantees: a bad template errors
-// here, and rendering cannot fail.
-// NewTemplate runs the same fences loadData does for a category, scoped to one
-// inline node with everything but checkNoCycles: a reference binds only into the
-// loaded tree, which has no path into this node, so rendering it cannot reach
-// itself. A new fence belongs in both places (loadData and here).
-func (f *Generator) NewTemplate(input string) (*Template, error) {
-	n, err := compileInput(input)
-	if err != nil {
-		return nil, fmt.Errorf("fejkdata: %w", err)
-	}
-	if err := linkNodeRefs(n, f.categories); err != nil {
-		return nil, fmt.Errorf("fejkdata: %w", err)
-	}
-	if err := checkNodeRepeatReach(n); err != nil {
-		return nil, fmt.Errorf("fejkdata: %w", err)
-	}
-	if err := checkNodeBoundLevelsHeld(n); err != nil {
-		return nil, fmt.Errorf("fejkdata: %w", err)
-	}
-	return &Template{g: f, n: n}, nil
-}
-
-// FakeTemplate compiles and renders an inline template in one call. It is
-// [NewTemplate] then [Template.Fake]; to render the same template many times, hold
-// the *Template and call its Fake.
-func (f *Generator) FakeTemplate(input string) (string, error) {
-	t, err := f.NewTemplate(input)
-	if err != nil {
-		return "", err
-	}
-	return t.Fake(), nil
-}
-
 // descend walks named fields to the node a path names. It is the one render-side
 // step that can fail, because the path comes from the caller and may name a field
 // that does not exist. A choice consumes no segment, so the rest of the path must