Refuse a calc over digits(0) or a repeat of 0, name an option's wrong kind as JSON does, type the name scope kinds, and compile only from a jsonvalue.Value

internal/builtinfunc/builtins.go

@@ -36,6 +36,9 @@ var builtins = withTransforms(map[string]builtin{
 	"nanoid": {arity: 1, checkArgs: countArg, prep: chars(nanoidAlphabet)},
 	"hex":    {arity: 1, checkArgs: countArg, prep: chars(hexDigits)},
 	"digits": {arity: 1, checkArgs: countArg, prep: chars("0123456789"), prints: datatype.String, proveNumber: func(token string, prints datatype.DataType, a []string) proven.Facts {
+		if atoi(a[0]) == 0 {
+			return proven.Unproven("{" + token + "} prints nothing, which is no number")
+		}
 		return proven.Printing(token, prints, proven.Bounded(0, math.Pow(10, float64(atoi(a[0])))-1, true))
 	}},
 	"upper": {arity: 1, checkArgs: countArg, prep: chars("ABCDEFGHIJKLMNOPQRSTUVWXYZ")},

internal/datafiles/datafiles.go

@@ -2,8 +2,6 @@
 package datafiles
 
 import (
-	"bytes"
-	"encoding/json"
 	"fmt"
 	"io/fs"
 	"os"
@@ -11,6 +9,7 @@ import (
 	"strings"
 
 	"github.com/larvit/fejkdata/internal/grammar"
+	"github.com/larvit/fejkdata/internal/jsonvalue"
 )
 
 // Source is one tree to load: an fs.FS and the directory in it to start from. label
@@ -35,7 +34,7 @@ func FS(fsys fs.FS, base string) Source { return Source{fsys: fsys, base: base}
 type Category struct {
 	Folders []string
 	Name    string
-	JSON    any
+	JSON    jsonvalue.Value
 	rows    *rowsFiles
 }
 
@@ -142,7 +141,7 @@ func (s Source) compileFile(dir []string, file string, rows *rowsFiles, compile
 	if err != nil {
 		return false, fmt.Errorf("%s: %w", s.labelled(full), err)
 	}
-	raw, err := DecodeJSON(b)
+	raw, err := jsonvalue.Decode(b)
 	if err != nil {
 		return false, fmt.Errorf("%s: %w", s.labelled(full), err)
 	}
@@ -179,14 +178,3 @@ func (r *rowsFiles) read(name string) (string, error) {
 	}
 	return string(b), nil
 }
-
-// DecodeJSON decodes one JSON value, keeping each number as the json.Number it is written as.
-func DecodeJSON(b []byte) (any, error) {
-	var v any
-	if !json.Valid(b) {
-		return nil, json.Unmarshal(b, &v)
-	}
-	dec := json.NewDecoder(bytes.NewReader(b))
-	dec.UseNumber()
-	return v, dec.Decode(&v)
-}

internal/datafiles/datafiles_test.go

@@ -20,7 +20,7 @@ func walk(t *testing.T, src Source) ([]handed, error) {
 	t.Helper()
 	var got []handed
 	err := src.Walk(func(c Category) error {
-		got = append(got, handed{c.Folders, c.Name, c.JSON})
+		got = append(got, handed{c.Folders, c.Name, c.JSON.Any()})
 		return nil
 	})
 	return got, err
@@ -133,7 +133,7 @@ func TestLoadHandsOneCategoryAndItsRows(t *testing.T) {
 	var got handed
 	var rows string
 	err := src.Load([]string{"sub"}, "t", func(c Category) error {
-		got = handed{c.Folders, c.Name, c.JSON}
+		got = handed{c.Folders, c.Name, c.JSON.Any()}
 		var err error
 		rows, err = c.ReadRows("t.tsv")
 		return err

internal/jsonvalue/jsonvalue.go

@@ -0,0 +1,39 @@
+// Package jsonvalue holds a decoded JSON value whose numbers keep the text they are written in.
+package jsonvalue
+
+import (
+	"bytes"
+	"encoding/json"
+)
+
+// Value is a JSON value that only Decode, String and Object make, so a template never compiles
+// from a value encoding/json decoded with its numbers as float64.
+type Value struct{ v any }
+
+// Decode decodes one JSON value, keeping each number as the json.Number it is written as.
+func Decode(b []byte) (Value, error) {
+	var v any
+	if !json.Valid(b) {
+		return Value{}, json.Unmarshal(b, &v)
+	}
+	dec := json.NewDecoder(bytes.NewReader(b))
+	dec.UseNumber()
+	err := dec.Decode(&v)
+	return Value{v}, err
+}
+
+// String is the JSON string s.
+func String(s string) Value { return Value{s} }
+
+// Object is the JSON object holding fields.
+func Object(fields map[string]Value) Value {
+	m := make(map[string]any, len(fields))
+	for k, f := range fields {
+		m[k] = f.v
+	}
+	return Value{m}
+}
+
+// Any is the value as encoding/json decodes it: a map[string]any, []any, string, json.Number,
+// bool or nil.
+func (v Value) Any() any { return v.v }