slog-handler-guide: handler example: Enabled method

Change-Id: I193980beda71ab8e20ccdd8a4eb0d72a9d2b32a0
Reviewed-on: https://go-review.googlesource.com/c/example/+/509956
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
Reviewed-by: Ian Cottrell <iancottrell@google.com>

Author: jba

slog-handler-guide/README.md

@@ -174,7 +174,14 @@ A handler's `Enabled` method could report whether the argument level
 is greater than or equal to the context value, allowing the verbosity
 of the work done by each request to be controlled independently.
 
-TODO(jba): include Enabled example
+Our `IndentHandler` doesn't use the context. It just compares the argument level
+with its configured minimum level:
+
+```
+func (h *IndentHandler) Enabled(ctx context.Context, level slog.Level) bool {
+	return level >= h.opts.Level.Level()
+}
+```
 
 ## The `Handle` method
 

slog-handler-guide/guide.md

@@ -137,7 +137,10 @@ A handler's `Enabled` method could report whether the argument level
 is greater than or equal to the context value, allowing the verbosity
 of the work done by each request to be controlled independently.
 
-TODO(jba): include Enabled example
+Our `IndentHandler` doesn't use the context. It just compares the argument level
+with its configured minimum level:
+
+%include indenthandler1/indent_handler.go enabled -
 
 ## The `Handle` method
 

slog-handler-guide/indenthandler1/indent_handler.go

@@ -40,10 +40,13 @@ func New(out io.Writer, opts *Options) *IndentHandler {
 
 //!-types
 
+// !+enabled
 func (h *IndentHandler) Enabled(ctx context.Context, level slog.Level) bool {
 	return level >= h.opts.Level.Level()
 }
 
+//!-enabled
+
 func (h *IndentHandler) WithGroup(name string) slog.Handler {
 	// TODO: implement.
 	return h
@@ -54,6 +57,7 @@ func (h *IndentHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
 	return h
 }
 
+// !+handle
 func (h *IndentHandler) Handle(ctx context.Context, r slog.Record) error {
 	buf := make([]byte, 0, 1024)
 	if !r.Time.IsZero() {
@@ -79,6 +83,9 @@ func (h *IndentHandler) Handle(ctx context.Context, r slog.Record) error {
 	return err
 }
 
+//!-handle
+
+// !+appendAttr
 func (h *IndentHandler) appendAttr(buf []byte, a slog.Attr, indentLevel int) []byte {
 	// Resolve the Attr's value before doing anything else.
 	a.Value = a.Value.Resolve()
@@ -115,3 +122,5 @@ func (h *IndentHandler) appendAttr(buf []byte, a slog.Attr, indentLevel int) []b
 	}
 	return buf
 }
+
+//!-appendAttr