feat(cmd): add version, plain json, struct inference and schema modes

Assisted-by: GLM 5.3 Flash
2026-09-22 00:55:02 +02:00
parent d18935ebc2
commit 3e741e7790
7 changed files with 951 additions and 14 deletions
@@ -0,0 +1,288 @@
+// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
+// SPDX-License-Identifier: MIT
+
+package main
+
+import (
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"io"
+	"path/filepath"
+	"reflect"
+	"strconv"
+	"strings"
+)
+
+// runSchema writes a TOML template for the named struct type of a Go source
+// file: one key per exported field, the comment a `comment=` tag option
+// carries printed above it, and a `default=` option as the value, or the
+// type's zero value where no default is given. Struct fields resolve into
+// [sections], slices of them into [[array of tables]] blocks, and an
+// untagged embedded struct flattens into its parent, the way the library
+// decodes it.
+func runSchema(typeName, sourcePath string, stdout io.Writer) error {
+	fset := token.NewFileSet()
+	file, err := parser.ParseFile(fset, sourcePath, nil, parser.ParseComments)
+	if err != nil {
+		return fmt.Errorf("%s: %w", filepath.Base(sourcePath), err)
+	}
+	types := declaredStructs(file)
+	st, ok := types[typeName]
+	if !ok {
+		return fmt.Errorf("no struct type %q in %s", typeName, filepath.Base(sourcePath))
+	}
+	body := &strings.Builder{}
+	writeSchemaFields(body, st, types, "")
+	_, err = io.WriteString(stdout, strings.TrimLeft(body.String(), "\n"))
+	return err
+}
+
+// declaredStructs collects the field lists of the file's top-level struct
+// type declarations.
+func declaredStructs(file *ast.File) map[string]*ast.StructType {
+	out := map[string]*ast.StructType{}
+	for _, decl := range file.Decls {
+		gd, ok := decl.(*ast.GenDecl)
+		if !ok {
+			continue
+		}
+		for _, spec := range gd.Specs {
+			ts, ok := spec.(*ast.TypeSpec)
+			if !ok {
+				continue
+			}
+			st, ok := ts.Type.(*ast.StructType)
+			if !ok {
+				continue
+			}
+			out[ts.Name.Name] = st
+		}
+	}
+	return out
+}
+
+// fieldMeta is what the generator reads off one struct field.
+type fieldMeta struct {
+	key     string
+	comment string
+	def     string
+	typ     ast.Expr
+}
+
+// writeSchemaFields writes the fields of one struct level: the scalar lines
+// first, then the sections, so the template re-parses with every value under
+// the header it belongs to. prefix is the dotted path the nested headers
+// carry.
+func writeSchemaFields(w *strings.Builder, st *ast.StructType, types map[string]*ast.StructType, prefix string) {
+	metas := metasOf(st, types)
+	for _, m := range metas {
+		if _, elemSt := elementStruct(m.typ, types); elemSt != nil {
+			continue
+		}
+		if isStructKind(m.typ, types) || isMapKind(m.typ) {
+			continue
+		}
+		writeComment(w, m.comment)
+		if _, ok := baseType(m.typ).(*ast.ArrayType); ok {
+			fmt.Fprintf(w, "%s = []\n", m.key)
+			continue
+		}
+		fmt.Fprintf(w, "%s = %s\n", m.key, scalarLiteral(m))
+	}
+	for _, m := range metas {
+		if !isStructKind(m.typ, types) && !isMapKind(m.typ) {
+			continue
+		}
+		writeComment(w, m.comment)
+		fmt.Fprintf(w, "[%s%s]\n", prefix, m.key)
+		if sub := structOf(m.typ, types); sub != nil {
+			writeSchemaFields(w, sub, types, prefix+m.key+".")
+		}
+		fmt.Fprintln(w)
+	}
+	for _, m := range metas {
+		_, elemSt := elementStruct(m.typ, types)
+		if elemSt == nil {
+			continue
+		}
+		writeComment(w, m.comment)
+		fmt.Fprintf(w, "[[%s%s]]\n", prefix, m.key)
+		writeSchemaFields(w, elemSt, types, "")
+		fmt.Fprintln(w)
+	}
+}
+
+// writeComment writes the comment lines above a binding.
+func writeComment(w *strings.Builder, text string) {
+	if text == "" {
+		return
+	}
+	for line := range strings.SplitSeq(text, "\n") {
+		fmt.Fprintf(w, "# %s\n", line)
+	}
+}
+
+// metasOf flattens the exported fields of a struct. The key comes from the
+// toml tag, or the lower-cased field name; a `-` key drops the field.
+func metasOf(st *ast.StructType, types map[string]*ast.StructType) []fieldMeta {
+	var out []fieldMeta
+	for _, field := range st.Fields.List {
+		if len(field.Names) == 0 {
+			// An untagged embedded struct flattens into the parent.
+			if ident, ok := baseType(field.Type).(*ast.Ident); ok {
+				if inner, ok := types[ident.Name]; ok {
+					out = append(out, metasOf(inner, types)...)
+				}
+			}
+			continue
+		}
+		name := field.Names[0].Name
+		if !ast.IsExported(name) {
+			continue
+		}
+		tagText := ""
+		if field.Tag != nil {
+			tagText, _ = strconv.Unquote(field.Tag.Value)
+		}
+		toml := reflect.StructTag(tagText).Get("toml")
+		key, opts := "", ""
+		if toml != "" {
+			key, opts, _ = strings.Cut(toml, ",")
+		}
+		if key == "-" {
+			continue
+		}
+		if key == "" {
+			key = strings.ToLower(name)
+		}
+		out = append(out, fieldMeta{
+			key:     key,
+			comment: tagOption(opts, "comment="),
+			def:     tagOption(opts, "default="),
+			typ:     field.Type,
+		})
+	}
+	return out
+}
+
+// tagOption returns the text a `name=` option carries in the option part of
+// a tag.
+func tagOption(opts, name string) string {
+	for opts != "" {
+		var opt string
+		opt, opts, _ = strings.Cut(opts, ",")
+		if text, ok := strings.CutPrefix(opt, name); ok {
+			return text
+		}
+	}
+	return ""
+}
+
+// baseType unwraps pointers and parentheses.
+func baseType(e ast.Expr) ast.Expr {
+	for {
+		switch x := e.(type) {
+		case *ast.StarExpr:
+			e = x.X
+		case *ast.ParenExpr:
+			e = x.X
+		default:
+			return e
+		}
+	}
+}
+
+// structOf returns the struct type an expression denotes when its
+// declaration sits in the same file, or when it is an anonymous struct.
+func structOf(e ast.Expr, types map[string]*ast.StructType) *ast.StructType {
+	if ident, ok := baseType(e).(*ast.Ident); ok {
+		return types[ident.Name]
+	}
+	if st, ok := baseType(e).(*ast.StructType); ok {
+		return st
+	}
+	return nil
+}
+
+// isStructKind reports whether the type is a struct the generator renders as
+// a section.
+func isStructKind(e ast.Expr, types map[string]*ast.StructType) bool {
+	return structOf(e, types) != nil
+}
+
+// isMapKind reports whether the type is a map, which renders as an empty
+// section.
+func isMapKind(e ast.Expr) bool {
+	_, ok := baseType(e).(*ast.MapType)
+	return ok
+}
+
+// elementStruct returns the struct type a slice's element denotes, for the
+// [[array of tables]] blocks.
+func elementStruct(e ast.Expr, types map[string]*ast.StructType) (ast.Expr, *ast.StructType) {
+	arr, ok := baseType(e).(*ast.ArrayType)
+	if !ok {
+		return nil, nil
+	}
+	return arr.Elt, structOf(arr.Elt, types)
+}
+
+// scalarLiteral renders the value line for a scalar field: the default=
+// option when it is set, and the type's zero value otherwise.
+func scalarLiteral(m fieldMeta) string {
+	kind := scalarKind(m.typ)
+	if m.def != "" {
+		if kind == "string" {
+			return strconv.Quote(m.def)
+		}
+		return m.def
+	}
+	switch kind {
+	case "int":
+		return "0"
+	case "float":
+		return "0.0"
+	case "bool":
+		return "false"
+	case "datetime":
+		return "1979-05-27T00:00:00Z"
+	}
+	return `""`
+}
+
+// scalarKind classifies a scalar type for the zero-value rendering.
+func scalarKind(e ast.Expr) string {
+	switch t := baseType(e).(type) {
+	case *ast.Ident:
+		switch t.Name {
+		case "bool":
+			return "bool"
+		case "float32", "float64":
+			return "float"
+		case "int", "int8", "int16", "int32", "int64",
+			"uint", "uint8", "uint16", "uint32", "uint64", "uintptr", "byte", "rune":
+			return "int"
+		}
+		if t.Name != "string" {
+			// A named type in the file may be a scalar alias; the string
+			// zero value is the safe default for it and everything unknown.
+			return "unknown"
+		}
+		return "string"
+	case *ast.SelectorExpr:
+		if pkg, ok := t.X.(*ast.Ident); ok {
+			if pkg.Name == "time" && t.Sel.Name == "Time" {
+				return "datetime"
+			}
+			if pkg.Name == "interpres" {
+				switch t.Sel.Name {
+				case "OffsetDateTime", "LocalDateTime", "LocalDate", "LocalTime":
+					return "datetime"
+				}
+			}
+		}
+	}
+	return "unknown"
+}