add hclogslog from github.com/evanphx/go-hclog-slog

hclogslog/README.md

@@ -0,0 +1,26 @@
+# hclogslog
+
+This is a go module that allows [hclog](https://github.com/hashicorp/go-hclog) to be used with
+[slog](https://pkg.go.dev/log/slog), a structured logging module that is
+included in Go 1.21 standard library.
+
+## Usage
+
+To create a slog logger from an existing `hclog.Logger` value:
+
+```
+
+var existing hclog.Logger
+
+...
+
+log := slog.New(hclogslog.Adapt(existing))
+
+```
+
+
+### Limitations
+
+Today, slog provides Time and PC values to the handlers. Currently these are ignored by the adapter because hclog
+doesn't provide a way for these to be overriden per-log message. If a future version of hclog
+adds the ability to process them per log, this adapter will be updated.

hclogslog/adapter.go

@@ -0,0 +1,204 @@
+package hclogslog
+
+import (
+	"context"
+	"log/slog"
+	"strconv"
+
+	"github.com/hashicorp/go-hclog"
+)
+
+func Adapt(l hclog.Logger) slog.Handler {
+	return &Handler{l: l}
+}
+
+type Handler struct {
+	l      hclog.Logger
+	prefix string
+}
+
+// Enabled reports whether the handler handles records at the given level.
+// The handler ignores records whose level is lower.
+// It is called early, before any arguments are processed,
+// to save effort if the log event should be discarded.
+// If called from a Logger method, the first argument is the context
+// passed to that method, or context.Background() if nil was passed
+// or the method does not take a context.
+// The context is passed so Enabled can use its values
+// to make a decision.
+func (h *Handler) Enabled(ctx context.Context, lvl slog.Level) bool {
+	switch {
+	case lvl < slog.LevelDebug:
+		return h.l.IsTrace()
+	case lvl < slog.LevelInfo:
+		return h.l.IsDebug()
+	case lvl < slog.LevelWarn:
+		return h.l.IsInfo()
+	case lvl < slog.LevelError:
+		return h.l.IsWarn()
+	default:
+		return h.l.IsError()
+	}
+}
+
+var basicTranslate = map[slog.Level]hclog.Level{
+	slog.LevelDebug - 4: hclog.Trace,
+	slog.LevelDebug:     hclog.Debug,
+	slog.LevelInfo:      hclog.Info,
+	slog.LevelWarn:      hclog.Warn,
+	slog.LevelError:     hclog.Error,
+}
+
+func (h *Handler) translateLevel(lvl slog.Level) hclog.Level {
+	if tl, ok := basicTranslate[lvl]; ok {
+		return tl
+	}
+
+	switch {
+	case lvl < slog.LevelDebug:
+		return hclog.Trace
+	case lvl < slog.LevelInfo:
+		return hclog.Debug
+	case lvl < slog.LevelWarn:
+		return hclog.Info
+	case lvl < slog.LevelError:
+		return hclog.Warn
+	default:
+		return hclog.Error
+	}
+}
+
+// processGroup walks through a Group and emits the total
+// hclog attributes to be emitted. This is called recursive in the chance
+// that there is a group in a group.
+func (h *Handler) processGroup(prefix string, a slog.Attr) []any {
+	var attrs []any
+
+	// If it's a group without a name, then ignore the group and process
+	// it like normal non-grouped attributes.
+	if a.Key == "" {
+		for _, subA := range a.Value.Group() {
+			if subA.Value.Kind() == slog.KindGroup {
+			} else {
+				attrs = append(attrs, prefix+subA.Key, subA.Value.Any())
+			}
+		}
+
+		return attrs
+	}
+
+	prefix = prefix + a.Key + "."
+
+	for i, subA := range a.Value.Group() {
+		attrs = append(attrs, h.processAttr(i, prefix, subA)...)
+	}
+
+	return attrs
+}
+
+func (h *Handler) processAttr(pos int, prefix string, a slog.Attr) []any {
+	val := a.Value.Resolve()
+
+	var attrs []any
+	if val.Kind() == slog.KindGroup {
+		attrs = append(attrs, h.processGroup(prefix, a)...)
+	} else {
+		key := a.Key
+		if key == "" {
+			if a.Value.Equal(slog.Value{}) {
+				return nil
+			}
+
+			// If the key is empty but there is a value, then make the key
+			// the position of the attributes in the record.
+			key = strconv.Itoa(pos)
+		}
+
+		attrs = append(attrs, prefix+key, val.Any())
+	}
+
+	return attrs
+}
+
+// Handle handles the Record.
+// It will only be called when Enabled returns true.
+// The Context argument is as for Enabled.
+// It is present solely to provide Handlers access to the context's values.
+// Canceling the context should not affect record processing.
+// (Among other things, log messages may be necessary to debug a
+// cancellation-related problem.)
+//
+// Handle methods that produce output should observe the following rules:
+//   - If r.Time is the zero time, ignore the time.
+//   - If r.PC is zero, ignore it.
+//   - Attr's values should be resolved.
+//   - If an Attr's key and value are both the zero value, ignore the Attr.
+//     This can be tested with attr.Equal(Attr{}).
+//   - If a group's key is empty, inline the group's Attrs.
+//   - If a group has no Attrs (even if it has a non-empty key),
+//     ignore it.
+func (h *Handler) Handle(_ context.Context, rec slog.Record) error {
+	attrs := make([]any, 0, rec.NumAttrs()*2)
+
+	var cnt int
+
+	rec.Attrs(func(a slog.Attr) bool {
+		attrs = append(attrs, h.processAttr(cnt, h.prefix, a)...)
+		cnt++
+		return true
+	})
+
+	h.l.Log(h.translateLevel(rec.Level), rec.Message, attrs...)
+	return nil
+}
+
+// WithAttrs returns a new Handler whose attributes consist of
+// both the receiver's attributes and the arguments.
+// The Handler owns the slice: it may retain, modify or discard it.
+
+func (h *Handler) WithAttrs(slogAttrs []slog.Attr) slog.Handler {
+	attrs := make([]any, 0, len(slogAttrs))
+
+	for i, a := range slogAttrs {
+		attrs = append(attrs, h.processAttr(i, h.prefix, a)...)
+	}
+
+	return &Handler{
+		l:      h.l.With(attrs...),
+		prefix: h.prefix,
+	}
+}
+
+// WithGroup returns a new Handler with the given group appended to
+// the receiver's existing groups.
+// The keys of all subsequent attributes, whether added by With or in a
+// Record, should be qualified by the sequence of group names.
+//
+// How this qualification happens is up to the Handler, so long as
+// this Handler's attribute keys differ from those of another Handler
+// with a different sequence of group names.
+//
+// A Handler should treat WithGroup as starting a Group of Attrs that ends
+// at the end of the log event. That is,
+//
+//	logger.WithGroup("s").LogAttrs(level, msg, slog.Int("a", 1), slog.Int("b", 2))
+//
+// should behave like
+//
+//	logger.LogAttrs(level, msg, slog.Group("s", slog.Int("a", 1), slog.Int("b", 2)))
+//
+// If the name is empty, WithGroup returns the receiver.
+func (h *Handler) WithGroup(name string) slog.Handler {
+	prefix := h.prefix
+
+	if name != "" {
+		prefix = h.prefix + name + "."
+	}
+
+	return &Handler{
+		l:      h.l,
+		prefix: prefix,
+	}
+}
+
+var _ slog.Handler = &Handler{}