feat(go-config): multi-format codecs, envc CLI, fixtures, ASRs

- Module github.com/eslider/go-config with env/yaml/json/ini packages
- internal: source, keymap, merge, structconv, bytesutil
- cmd/envc: convert, get, merge
- docs/asr ASR-0001..0008, README/CHANGELOG/AGENTS refresh
- golangci-lint v2 config; tests + fixtures

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

internal/structconv/structconv.go

@@ -0,0 +1,74 @@
+// Package structconv wraps mapstructure for map<->struct conversion.
+package structconv
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	"github.com/go-viper/mapstructure/v2"
+)
+
+// Options configures Decode and Encode.
+type Options struct {
+	TagName     string
+	WeaklyTyped bool
+	Trim        bool
+	ExtraHooks  []mapstructure.DecodeHookFunc
+}
+
+func trimStringHook(from, to reflect.Type, data any) (any, error) {
+	if from.Kind() == reflect.String && to.Kind() == reflect.String {
+		if s, ok := data.(string); ok {
+			return strings.TrimSpace(s), nil
+		}
+	}
+	return data, nil
+}
+
+func composeHooks(o Options) mapstructure.DecodeHookFunc {
+	var hooks []mapstructure.DecodeHookFunc
+	if o.Trim {
+		hooks = append(hooks, trimStringHook)
+	}
+	hooks = append(hooks, o.ExtraHooks...)
+	if len(hooks) == 0 {
+		return nil
+	}
+	return mapstructure.ComposeDecodeHookFunc(hooks...)
+}
+
+// Decode maps in into struct or map dst (dst must be pointer).
+func Decode(in map[string]any, dst any, o Options) error {
+	tag := o.TagName
+	if tag == "" {
+		tag = "mapstructure"
+	}
+	cfg := &mapstructure.DecoderConfig{
+		Result:           dst,
+		WeaklyTypedInput: o.WeaklyTyped,
+		TagName:          tag,
+		DecodeHook:       composeHooks(o),
+	}
+	dec, err := mapstructure.NewDecoder(cfg)
+	if err != nil {
+		return fmt.Errorf("structconv: decoder: %w", err)
+	}
+	if err := dec.Decode(in); err != nil {
+		return fmt.Errorf("structconv: decode: %w", err)
+	}
+	return nil
+}
+
+// Encode flattens src (struct or map) into a new map[string]any.
+func Encode(src any) (map[string]any, error) {
+	out := make(map[string]any)
+	dec, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{Result: &out})
+	if err != nil {
+		return nil, fmt.Errorf("structconv: encoder: %w", err)
+	}
+	if err := dec.Decode(src); err != nil {
+		return nil, fmt.Errorf("structconv: encode: %w", err)
+	}
+	return out, nil
+}

internal/structconv/structconv_test.go

@@ -0,0 +1,28 @@
+package structconv
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestDecodeEncodeRoundTrip(t *testing.T) {
+	type nested struct {
+		V int `mapstructure:"v"`
+	}
+	type root struct {
+		A nested `mapstructure:"a"`
+	}
+	in := map[string]any{"a": map[string]any{"v": 7}}
+	var dst root
+	if err := Decode(in, &dst, Options{WeaklyTyped: true, Trim: true}); err != nil {
+		t.Fatal(err)
+	}
+	out, err := Encode(&dst)
+	if err != nil {
+		t.Fatal(err)
+	}
+	am := out["a"].(map[string]any)
+	if fmt.Sprint(am["v"]) != "7" {
+		t.Fatalf("%#v", out)
+	}
+}