feat(cli): hide redundant log attributes

internal/ui/slog_handler.go

@@ -8,6 +8,9 @@ import (
 	"sync"
 )
 
+// Developed with guidance from golang docs:
+// https://github.com/golang/example/blob/32022caedd6a177a7717aa8680cbe179e1045935/slog-handler-guide/README.md
+
 const (
 	ansiClear      = "\033[0m"
 	ansiBold       = "\033[1m"
@@ -23,8 +26,41 @@ type Handler struct {
 	out  io.Writer
 }
 
+// HandlerOptions are a subset of [slog.HandlerOptions] that are implemented for the UI handler.
 type HandlerOptions struct {
+	// Level reports the minimum record level that will be logged.
+	// The handler discards records with lower levels.
+	// If Level is nil, the handler assumes LevelInfo.
+	// The handler calls Level.Level for each record processed;
+	// to adjust the minimum level dynamically, use a LevelVar.
 	Level slog.Leveler
+
+	// ReplaceAttr is called to rewrite each non-group attribute before it is logged.
+	// The attribute's value has been resolved (see [Value.Resolve]).
+	// If ReplaceAttr returns a zero Attr, the attribute is discarded.
+	//
+	// The built-in attributes with keys "time", "level", "source", and "msg"
+	// are passed to this function, except that time is omitted
+	// if zero, and source is omitted if AddSource is false.
+	//
+	// The first argument is a list of currently open groups that contain the
+	// Attr. It must not be retained or modified. ReplaceAttr is never called
+	// for Group attributes, only their contents. For example, the attribute
+	// list
+	//
+	//     Int("a", 1), Group("g", Int("b", 2)), Int("c", 3)
+	//
+	// results in consecutive calls to ReplaceAttr with the following arguments:
+	//
+	//     nil, Int("a", 1)
+	//     []string{"g"}, Int("b", 2)
+	//     nil, Int("c", 3)
+	//
+	// ReplaceAttr can be used to change the default keys of the built-in
+	// attributes, convert types (for example, to replace a `time.Time` with the
+	// integer seconds since the Unix epoch), sanitize personal information, or
+	// remove attributes from the output.
+	ReplaceAttr func(groups []string, a slog.Attr) slog.Attr
 }
 
 // groupOrAttrs holds either a group name or a list of [slog.Attr].
@@ -108,6 +144,12 @@ func (h *Handler) Handle(_ context.Context, record slog.Record) error {
 
 func (h *Handler) appendAttr(buf []byte, group string, a slog.Attr) []byte {
 	a.Value = a.Value.Resolve()
+
+	if h.opts.ReplaceAttr != nil {
+		a = h.opts.ReplaceAttr([]string{group}, a)
+	}
+
+	// No-op if null attr
 	if a.Equal(slog.Attr{}) {
 		return buf
 	}