swap from standalone attrs call to slog.LogValuer interface

README.md

@@ -9,7 +9,7 @@ Mirror: https://github.com/wisehodl/go-mana-component
 
 - Injects a named component identity into a `context.Context` at library boundaries
 - Propagates module identity and component hierarchy across layers
-- Provides `slog` attributes for structured logging and a string map for generic consumers
+- Implements `slog.LogValuer` for use as a structured log attribute, and provides a string map for generic consumers
 
 ## What this library does not do
 
@@ -40,15 +40,15 @@ constructs a logger internally.
 ### At a library boundary
 
 A top-level constructor receives a context and creates a new component
-identity. Injecting the component attributes on the logger allows it to carry
-`module` and `path` automatically.
+identity. Passing the component as a `slog.Any` group attribute allows the
+logger to carry `module` and `path` automatically.
 
 ```go
 func NewPool(ctx context.Context, id string, handler slog.Handler) (*Pool, error) {
     ctx = component.MustNew(ctx, "honeybee", "outbound_pool")
 
-    attrs, _ := component.Attrs(ctx)
-    logger := slog.New(handler).WithAttrs(attrs).With(slog.String("pool_id", id))
+    c, _ := component.Get(ctx)
+    logger := slog.New(handler).With(slog.Any("component", c), slog.String("pool_id", id))
 
     return &Pool{ctx: ctx, logger: logger}, nil
 }
@@ -63,8 +63,8 @@ path. No parent identifiers need to be passed as arguments.
 func NewWorker(ctx context.Context, id string, handler slog.Handler) (*Worker, error) {
     ctx = component.MustExtend(ctx, "outbound_worker")
 
-    attrs, _ := component.Attrs(ctx)
-    logger := slog.New(handler).WithAttrs(attrs).With(slog.Any("peer_id", id))
+    c, _ := component.Get(ctx)
+    logger := slog.New(handler).With(slog.Any("component", c), slog.Any("peer_id", id))
 
     return &Worker{ctx: ctx, logger: logger}, nil
 }

main.go

@@ -17,6 +17,7 @@ type Component interface {
 	Module() string
 	Path() []string
 	PathString() string
+	LogValue() slog.Value
 }
 
 type component struct {
@@ -27,6 +28,12 @@ type component struct {
 func (c component) Module() string     { return c.module }
 func (c component) Path() []string     { return slices.Clone(c.path) }
 func (c component) PathString() string { return strings.Join(c.path, ".") }
+func (c component) LogValue() slog.Value {
+	return slog.GroupValue(
+		slog.String("module", c.module),
+		slog.String("path", c.PathString()),
+	)
+}
 
 func insert(ctx context.Context, module string, name string, path []string) context.Context {
 	return context.WithValue(ctx, storageKey, component{
@@ -117,16 +124,3 @@ func GetFields(ctx context.Context) (map[string]string, bool) {
 		"path":   c.PathString(),
 	}, true
 }
-
-// Attrs returns the slog projection of GetFields.
-func Attrs(ctx context.Context) ([]slog.Attr, bool) {
-	fields, ok := GetFields(ctx)
-	if !ok {
-		return nil, false
-	}
-
-	return []slog.Attr{
-		slog.String("module", fields["module"]),
-		slog.String("path", fields["path"]),
-	}, true
-}

main_test.go

@@ -2,7 +2,6 @@ package component
 
 import (
 	"context"
-	"log/slog"
 	"slices"
 	"testing"
 )
@@ -120,22 +119,18 @@ func TestGetFields(t *testing.T) {
 	}
 }
 
-func assertAttr(t *testing.T, attr slog.Attr, key string, value string) {
-	t.Helper()
-	if attr.Key != key {
-		t.Errorf("expected attr key %q, got %q", key, attr.Key)
-	}
-	if attr.Value.String() != value {
-		t.Errorf("expected attr value %q, got %q", value, attr.Value.String())
-	}
-}
-
-func TestAttrs(t *testing.T) {
+func TestLogValue(t *testing.T) {
 	ctx := MustNew(context.Background(), "mymodule", "mycomponent")
-	attrs, ok := Attrs(ctx)
-	if !ok {
-		t.Fatal("expected attrs in context")
+	c, _ := Get(ctx)
+	v := c.LogValue()
+	attrs := v.Group()
+	if len(attrs) != 2 {
+		t.Fatalf("expected 2 attrs, got %d", len(attrs))
+	}
+	if attrs[0].Key != "module" || attrs[0].Value.String() != "mymodule" {
+		t.Errorf("expected module=mymodule, got %s=%s", attrs[0].Key, attrs[0].Value.String())
+	}
+	if attrs[1].Key != "path" || attrs[1].Value.String() != "mycomponent" {
+		t.Errorf("expected path=mycomponent, got %s=%s", attrs[1].Key, attrs[1].Value.String())
 	}
-	assertAttr(t, attrs[0], "module", "mymodule")
-	assertAttr(t, attrs[1], "path", "mycomponent")
 }