feat: add TOML codec and envc format support

New toml package (pelletier/go-toml/v2) matching yaml/json options and merge flow.
envc convert/get/merge accept --from/--to toml; fixture and CLI tests; docs refresh.

Co-authored-by: Cursor <cursoragent@cursor.com>

AGENTS.md

@@ -4,11 +4,11 @@ This module is part of the eSlider `go-*` library standard (inventar ASR-0008).
 
 ## Purpose
 
-Convert **env**, **YAML**, **JSON**, and **INI** into nested `map[string]any` and Go structs (and back), with multi-source merging and the `envc` CLI.
+Convert **env**, **YAML**, **JSON**, **TOML**, and **INI** into nested `map[string]any` and Go structs (and back), with multi-source merging and the `envc` CLI.
 
 ## Public API surface
 
-- Subpackages: `env`, `yaml`, `json`, `ini` — each exports `New`, `(*Codec).Map`, `Unmarshal`, `UnmarshalContext`, `Marshal`, `WriteTo`, and format-specific options.
+- Subpackages: `env`, `yaml`, `json`, `toml`, `ini` — each exports `New`, `(*Codec).Map`, `Unmarshal`, `UnmarshalContext`, `Marshal`, `WriteTo`, and format-specific options.
 - `cmd/envc` — binary `envc`: `convert`, `get`, `merge`.
 - Internals under `internal/` are not stable API.
 

README.md

@@ -8,14 +8,14 @@
 [![Go Report Card](https://goreportcard.com/badge/github.com/eslider/go-config)](https://goreportcard.com/report/github.com/eslider/go-config)
 [![GitHub Stars](https://img.shields.io/github/stars/eSlider/go-config?style=social)](https://github.com/eSlider/go-config/stargazers)
 
-Convert **env**, **YAML**, **JSON**, and **INI** to and from Go `map[string]any` and structs. Multi-source inputs merge with **deep map merge**: nested maps combine, **scalar leaves are last-write-wins**, and **slices** default to **replace** (opt-in **concat** via `WithSliceMerge`). Keys are normalized with a configurable **lower+alnum** rule so `sub-service`, `SUB_SERVICE`, and `SubService` line up across formats. Built on [go-viper/mapstructure/v2](https://github.com/go-viper/mapstructure).
+Convert **env**, **YAML**, **JSON**, **TOML**, and **INI** to and from Go `map[string]any` and structs. Multi-source inputs merge with **deep map merge**: nested maps combine, **scalar leaves are last-write-wins**, and **slices** default to **replace** (opt-in **concat** via `WithSliceMerge`). Keys are normalized with a configurable **lower+alnum** rule so `sub-service`, `SUB_SERVICE`, and `SubService` line up across formats. Built on [go-viper/mapstructure/v2](https://github.com/go-viper/mapstructure).
 
 ## Architecture
 
 ```mermaid
 flowchart TB
   Sources["Sources\nbytes reader file URL process env"]
-  Parser["Parser\ngodotenv yaml ini json"]
+  Parser["Parser\ngodotenv yaml json toml ini"]
   Norm["keymap.Walk\nNormalizer"]
   MergeOp["merge.DeepMerge"]
   Map["map string any"]
@@ -88,8 +88,8 @@ os.WriteFile("out.json", b, 0o644)
 ## CLI: `envc`
 
 Install the binary from [**Install**](#install) (`go install …/cmd/envc@latest`). Every
-subcommand uses **`--from`** and **`--to`** with one of **`yaml`**, **`json`**, **`ini`**,
+subcommand uses **`--from`** and **`--to`** with one of **`yaml`**, **`json`**, **`toml`**,
-**`env`**. Snippets use **`bash`** so you can copy-paste; replace paths and URLs with yours.
+**`ini`**, **`env`**. Snippets use **`bash`** so you can copy-paste; replace paths and URLs with yours.
 
 ### Help and version
 
@@ -121,6 +121,9 @@ envc convert --from json --to yaml --input ./settings.json --output ./settings.y
 # Windows-style INI → JSON for a one-off jq filter
 envc convert --from ini --to json --input ./odbc.ini --output ./odbc.json
 
+# TOML (e.g. app / tool config) → YAML for a stack that only reads YAML
+envc convert --from toml --to yaml --input ./config.toml --output ./config.yaml
+
 # Remote YAML → materialize .env for `docker compose --env-file` or similar
 envc convert --from yaml --to env \
   --input "https://raw.githubusercontent.com/org/stack/main/config.yaml" \
@@ -186,6 +189,11 @@ set -a
 source <(envc convert --from ini --to env --input ./legacy.ini)
 set +a
 
+# TOML tool manifest or stack file → env in the shell
+set -a
+source <(envc convert --from toml --to env --input ./stack.toml)
+set +a
+
 # Inline YAML here-doc → env → source (CI or local; no intermediate file)
 set -a
 source <(cat <<'YAML' | envc convert --from yaml --to env
@@ -213,7 +221,7 @@ envc convert --from json --to yaml \
   --output ./snapshot.yaml
 ```
 
-## API (all codecs)
+## API (format codecs)
 
 | Method                                          | Description                       |
 | ----------------------------------------------- | --------------------------------- |
@@ -234,6 +242,8 @@ Shared options (each subpackage): `WithBytes`, `WithReader`, `WithFile`, `WithUR
 
 INI uses dotted sections, e.g. `[service.subservice]` with `name=...`.
 
+TOML uses explicit tables, e.g. `[service]`, `[service.subservice]`, with `name = "..."`.
+
 ## Related libraries
 
 | Module                                                    | Role           |

cmd/envc/convert.go

@@ -11,6 +11,7 @@ import (
 	"github.com/eslider/go-config/ini"
 	"github.com/eslider/go-config/internal/bytesutil"
 	libjson "github.com/eslider/go-config/json"
+	"github.com/eslider/go-config/toml"
 	"github.com/eslider/go-config/yaml"
 	yaml3 "gopkg.in/yaml.v3"
 )
@@ -19,8 +20,8 @@ import (
 func RunConvert(args []string, stdin io.Reader, stdout, stderr io.Writer) int {
 	fs := flag.NewFlagSet("convert", flag.ContinueOnError)
 	fs.SetOutput(stderr)
-	from := fs.String("from", "", "source format: yaml|json|ini|env")
+	from := fs.String("from", "", "source format: yaml|json|toml|ini|env")
-	to := fs.String("to", "", "target format: yaml|json|ini|env")
+	to := fs.String("to", "", "target format: yaml|json|toml|ini|env")
 	input := fs.String("input", "-", "input path, URL, or - for stdin")
 	output := fs.String("output", "-", "output path or - for stdout")
 	if err := fs.Parse(args); err != nil {
@@ -75,6 +76,8 @@ func loadMapFromBytes(ctx context.Context, format string, b []byte) (map[string]
 		return ini.New(ini.WithBytes(b)).Map(ctx)
 	case "env":
 		return env.New(env.WithBytes(b)).Map(ctx)
+	case "toml":
+		return toml.New(toml.WithBytes(b)).Map(ctx)
 	default:
 		return nil, fmt.Errorf("unknown format %q", format)
 	}
@@ -90,6 +93,8 @@ func marshalMap(format string, m map[string]any) ([]byte, error) {
 		return ini.New().Marshal(m)
 	case "env":
 		return env.New().Marshal(m)
+	case "toml":
+		return toml.New().Marshal(m)
 	default:
 		return nil, fmt.Errorf("unknown format %q", format)
 	}

cmd/envc/convert_test.go

@@ -8,6 +8,18 @@ import (
 	"testing"
 )
 
+func TestRunConvert_TOMLToJSON(t *testing.T) {
+	var stdout, stderr bytes.Buffer
+	stdin := strings.NewReader("[app]\nport = 8080\n")
+	code := RunConvert([]string{"--from", "toml", "--to", "json", "--input", "-"}, stdin, &stdout, &stderr)
+	if code != 0 {
+		t.Fatalf("stderr: %s", stderr.String())
+	}
+	if !strings.Contains(stdout.String(), `"port"`) || !strings.Contains(stdout.String(), "8080") {
+		t.Fatalf("out: %s", stdout.String())
+	}
+}
+
 func TestRunConvert_YAMLToJSON(t *testing.T) {
 	var stdout, stderr bytes.Buffer
 	stdin := strings.NewReader("a: 1\n")

cmd/envc/doc.go

@@ -1,3 +1,3 @@
 // Command envc converts, queries, and merges configuration between env, YAML,
-// JSON, and INI formats.
+// JSON, TOML, and INI formats.
 package main

cmd/envc/get.go

@@ -16,7 +16,7 @@ import (
 func RunGet(args []string, stdin io.Reader, stdout, stderr io.Writer) int {
 	fs := flag.NewFlagSet("get", flag.ContinueOnError)
 	fs.SetOutput(stderr)
-	from := fs.String("from", "", "format: yaml|json|ini|env")
+	from := fs.String("from", "", "format: yaml|json|toml|ini|env")
 	path := fs.String("path", "", "dot-separated path (e.g. service.subservice.name)")
 	if err := fs.Parse(args); err != nil {
 		return 2

cmd/envc/main.go

@@ -16,7 +16,7 @@ var (
 
 // printUsage writes the root help text to w.
 func printUsage(w io.Writer) {
-	_, _ = io.WriteString(w, `envc — convert, query, and merge configuration across env, YAML, JSON, and INI.
+	_, _ = io.WriteString(w, `envc — convert, query, and merge configuration across env, YAML, JSON, TOML, and INI.
 
 Usage:
   envc <command> [arguments]

cmd/envc/merge.go

@@ -15,8 +15,8 @@ import (
 func RunMerge(args []string, stdin io.Reader, stdout, stderr io.Writer) int {
 	fs := flag.NewFlagSet("merge", flag.ContinueOnError)
 	fs.SetOutput(stderr)
-	from := fs.String("from", "", "input format: yaml|json|ini|env")
+	from := fs.String("from", "", "input format: yaml|json|toml|ini|env")
-	to := fs.String("to", "", "output format: yaml|json|ini|env")
+	to := fs.String("to", "", "output format: yaml|json|toml|ini|env")
 	output := fs.String("output", "-", "output path or - for stdout")
 	if err := fs.Parse(args); err != nil {
 		return 2

doc.go

@@ -1,6 +1,6 @@
 // Package config is the module root for go-config (import path
-// github.com/eslider/go-config). Use the subpackages [env], [yaml], [json], and
+// github.com/eslider/go-config). Use the subpackages [env], [yaml], [json], [toml],
-// [ini] for format-specific codecs and the [cmd/envc] command for CLI
+// and [ini] for format-specific codecs and the [cmd/envc] command for CLI
 // conversion.
 //
 // Hero workflow (YAML + layered dotenv + process env):
@@ -19,5 +19,6 @@
 // [env]: https://pkg.go.dev/github.com/eslider/go-config/env
 // [yaml]: https://pkg.go.dev/github.com/eslider/go-config/yaml
 // [json]: https://pkg.go.dev/github.com/eslider/go-config/json
+// [toml]: https://pkg.go.dev/github.com/eslider/go-config/toml
 // [ini]: https://pkg.go.dev/github.com/eslider/go-config/ini
 package config

fixtures/identity/service.toml

@@ -0,0 +1,12 @@
+[service]
+name = "my-service"
+
+[service.sub-service]
+name = "abc"
+key = "abs"
+timeout = 30
+enabled = true
+
+[service.database]
+url = "postgres://localhost:5432/db"
+pool-size = 10

go.mod

@@ -5,6 +5,7 @@ go 1.22.2
 require (
 	github.com/go-viper/mapstructure/v2 v2.5.0
 	github.com/joho/godotenv v1.5.1
+	github.com/pelletier/go-toml/v2 v2.2.3
 	gopkg.in/ini.v1 v1.67.0
 	gopkg.in/yaml.v3 v3.0.1
 )

go.sum

@@ -4,6 +4,8 @@ github.com/go-viper/mapstructure/v2 v2.5.0 h1:vM5IJoUAy3d7zRSVtIwQgBj7BiWtMPfmPE
 github.com/go-viper/mapstructure/v2 v2.5.0/go.mod h1:oJDH3BJKyqBA2TXFhDsKDGDTlndYOZ6rGS0BRZIxGhM=
 github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
 github.com/joho/godotenv v1.5.1/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=
+github.com/pelletier/go-toml/v2 v2.2.3 h1:YmeHyLY8mFWbdkNWwpr+qIL2bEqT0o95WSdkNHvL12M=
+github.com/pelletier/go-toml/v2 v2.2.3/go.mod h1:MfCQTFTvCcUyyvvwm1+G6H/jORL20Xlb6rzQu9GuUkc=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=

toml/codec.go

@@ -0,0 +1,117 @@
+package toml
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+
+	"github.com/eslider/go-config/internal/bytesutil"
+	"github.com/eslider/go-config/internal/keymap"
+	"github.com/eslider/go-config/internal/merge"
+	"github.com/eslider/go-config/internal/source"
+	"github.com/eslider/go-config/internal/structconv"
+	toml2 "github.com/pelletier/go-toml/v2"
+)
+
+// Codec loads TOML from multiple sources.
+type Codec struct {
+	sources    []source.Source
+	normalizer keymap.Normalizer
+	sliceStrat merge.SliceStrategy
+	structOpts structconv.Options
+	mergeOpts  []merge.Option
+	httpClient *http.Client
+	urlHeader  http.Header
+}
+
+// New creates a TOML codec.
+func New(opts ...Option) *Codec {
+	c := &Codec{
+		normalizer: keymap.LowerAlnum,
+		sliceStrat: merge.Replace,
+		structOpts: structconv.Options{
+			TagName:     "mapstructure",
+			WeaklyTyped: true,
+			Trim:        true,
+		},
+	}
+	for _, o := range opts {
+		o(c)
+	}
+	c.mergeOpts = []merge.Option{merge.WithSliceStrategy(c.sliceStrat)}
+	return c
+}
+
+// Map merges all TOML sources into one map.
+func (c *Codec) Map(ctx context.Context) (map[string]any, error) {
+	if len(c.sources) == 0 {
+		return nil, fmt.Errorf("toml: no sources")
+	}
+	acc := make(map[string]any)
+	for _, s := range c.sources {
+		b, err := bytesutil.ReadAll(ctx, s)
+		if err != nil {
+			return nil, fmt.Errorf("toml: read %s: %w", s.String(), err)
+		}
+		var parsed map[string]any
+		if err := toml2.Unmarshal(b, &parsed); err != nil {
+			return nil, fmt.Errorf("toml: parse %s: %w", s.String(), err)
+		}
+		if parsed == nil {
+			parsed = map[string]any{}
+		}
+		merge.DeepMerge(acc, parsed, c.mergeOpts...)
+	}
+	if c.normalizer != nil {
+		keymap.Walk(acc, c.normalizer)
+	}
+	return acc, nil
+}
+
+// Unmarshal decodes using context.Background.
+func (c *Codec) Unmarshal(dst any) error {
+	return c.UnmarshalContext(context.Background(), dst)
+}
+
+// UnmarshalContext decodes merged TOML into dst.
+func (c *Codec) UnmarshalContext(ctx context.Context, dst any) error {
+	m, err := c.Map(ctx)
+	if err != nil {
+		return err
+	}
+	return structconv.Decode(m, dst, c.structOpts)
+}
+
+// Marshal encodes src to TOML bytes (struct or map[string]any).
+func (c *Codec) Marshal(src any) ([]byte, error) {
+	m, err := encodeToMap(src)
+	if err != nil {
+		return nil, fmt.Errorf("toml: encode: %w", err)
+	}
+	var buf bytes.Buffer
+	enc := toml2.NewEncoder(&buf)
+	enc.SetIndentTables(true)
+	if err := enc.Encode(m); err != nil {
+		return nil, fmt.Errorf("toml: marshal: %w", err)
+	}
+	return buf.Bytes(), nil
+}
+
+// WriteTo writes TOML to w.
+func (c *Codec) WriteTo(w io.Writer, src any) (int64, error) {
+	b, err := c.Marshal(src)
+	if err != nil {
+		return 0, err
+	}
+	n, err := w.Write(b)
+	return int64(n), err
+}
+
+func encodeToMap(src any) (map[string]any, error) {
+	if m, ok := src.(map[string]any); ok {
+		return m, nil
+	}
+	return structconv.Encode(src)
+}

toml/codec_test.go

@@ -0,0 +1,41 @@
+package toml
+
+import (
+	"context"
+	"testing"
+
+	"github.com/eslider/go-config/internal/testfixtures"
+)
+
+func TestCodec_IdentityTOMLFixture(t *testing.T) {
+	c := New(WithBytes(testfixtures.Load(t, "identity", "service.toml")))
+	m, err := c.Map(context.Background())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if m["service"].(map[string]any)["name"] != "my-service" {
+		t.Fatalf("%#v", m)
+	}
+}
+
+func TestCodec_MarshalRoundTripMap(t *testing.T) {
+	in := map[string]any{
+		"app": map[string]any{
+			"name": "demo",
+			"port": int64(8080),
+		},
+	}
+	c := New()
+	b, err := c.Marshal(in)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c2 := New(WithBytes(b))
+	m, err := c2.Map(context.Background())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if m["app"].(map[string]any)["name"] != "demo" {
+		t.Fatalf("%#v", m)
+	}
+}

toml/doc.go

@@ -0,0 +1,3 @@
+// Package toml loads and writes TOML configuration using the shared codec pattern
+// (sources, deep merge, key normalization, struct decode via mapstructure).
+package toml

toml/options.go

@@ -0,0 +1,87 @@
+package toml
+
+import (
+	"io"
+	"net/http"
+
+	"github.com/eslider/go-config/internal/keymap"
+	"github.com/eslider/go-config/internal/merge"
+	"github.com/eslider/go-config/internal/source"
+	"github.com/go-viper/mapstructure/v2"
+)
+
+// Option configures a Codec.
+type Option func(*Codec)
+
+// WithBytes appends TOML from bytes.
+func WithBytes(b []byte) Option {
+	return func(c *Codec) { c.sources = append(c.sources, source.Bytes{Data: b, Name: "bytes"}) }
+}
+
+// WithReader appends TOML from r.
+func WithReader(r io.Reader) Option {
+	return func(c *Codec) { c.sources = append(c.sources, source.Reader{R: r, Name: "reader"}) }
+}
+
+// WithFile appends a TOML file path.
+func WithFile(path string) Option {
+	return func(c *Codec) { c.sources = append(c.sources, source.File{Path: path}) }
+}
+
+// WithURL appends TOML from an HTTP(S) URL.
+func WithURL(raw string) Option {
+	return func(c *Codec) {
+		var hdr http.Header
+		if c.urlHeader != nil {
+			hdr = c.urlHeader.Clone()
+		}
+		c.sources = append(c.sources, source.URL{Raw: raw, Header: hdr, HTTPClient: c.httpClient})
+	}
+}
+
+// WithHTTPClient sets the client for subsequent WithURL sources.
+func WithHTTPClient(client *http.Client) Option {
+	return func(c *Codec) { c.httpClient = client }
+}
+
+// WithHTTPHeader adds a header for subsequent WithURL sources.
+func WithHTTPHeader(k, v string) Option {
+	return func(c *Codec) {
+		if c.urlHeader == nil {
+			c.urlHeader = make(http.Header)
+		}
+		c.urlHeader.Add(k, v)
+	}
+}
+
+// WithKeyNormalizer sets key normalizer after merge (nil disables).
+func WithKeyNormalizer(n keymap.Normalizer) Option {
+	return func(c *Codec) { c.normalizer = n }
+}
+
+// WithSliceMerge sets slice merge strategy across sources.
+func WithSliceMerge(s merge.SliceStrategy) Option {
+	return func(c *Codec) { c.sliceStrat = s }
+}
+
+// WithTrim toggles string trim on struct decode.
+func WithTrim(enable bool) Option {
+	return func(c *Codec) { c.structOpts.Trim = enable }
+}
+
+// WithWeaklyTyped toggles weak typing for struct decode.
+func WithWeaklyTyped(enable bool) Option {
+	return func(c *Codec) { c.structOpts.WeaklyTyped = enable }
+}
+
+// WithTagName sets mapstructure tag name.
+func WithTagName(name string) Option {
+	return func(c *Codec) { c.structOpts.TagName = name }
+}
+
+// WithDecodeHook appends a decode hook.
+func WithDecodeHook(h mapstructure.DecodeHookFunc) Option {
+	return func(c *Codec) {
+		c.structOpts.ExtraHooks = append(c.structOpts.ExtraHooks, h)
+	}
+}