Problem with logging after introducing logr

[antoniomacri]

Description

It seems that the logger is being called with its varargs as format arguments, but logr wants a list of key-values.

Environment

module main

go 1.19

require (
	github.com/go-logr/stdr v1.2.2
	go.opentelemetry.io/otel v1.16.0
	go.opentelemetry.io/otel/exporters/zipkin v1.16.0
	go.opentelemetry.io/otel/sdk v1.16.0
	go.opentelemetry.io/otel/trace v1.16.0
)

require (
	github.com/go-logr/logr v1.2.4 // indirect
	github.com/openzipkin/zipkin-go v0.4.1 // indirect
	go.opentelemetry.io/otel/metric v1.16.0 // indirect
	golang.org/x/sys v0.8.0 // indirect
)

Steps To Reproduce

package main

import (
	"context"
	"github.com/go-logr/stdr"
	"go.opentelemetry.io/otel/codes"
	"go.opentelemetry.io/otel/exporters/zipkin"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	"go.opentelemetry.io/otel/sdk/trace/tracetest"
	"go.opentelemetry.io/otel/trace"
	"log"
	"os"
	"time"
)

func main() {
	exporter, err := zipkin.New("http://localhost:9411/api/v2/spans", zipkin.WithLogr(stdr.New(log.New(os.Stdout, "", 0))))
	if err != nil {
		log.Fatalf("cannot initialize the application tracer: %v1", err)
	}
	err = exporter.ExportSpans(context.Background(), tracetest.SpanStubs{{
		SpanContext: trace.NewSpanContext(trace.SpanContextConfig{
			TraceID: trace.TraceID{0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F},
			SpanID:  trace.SpanID{0xFF, 0xFE, 0xFD, 0xFC, 0xFB, 0xFA, 0xF9, 0xF8},
		}),
		SpanKind:   trace.SpanKindServer,
		Name:       "foo",
		StartTime:  time.Date(2020, time.March, 11, 19, 24, 0, 0, time.UTC),
		EndTime:    time.Date(2020, time.March, 11, 19, 25, 0, 0, time.UTC),
		Attributes: nil,
		Events:     nil,
		Status: sdktrace.Status{
			Code:        codes.Error,
			Description: "404, file not found",
		},
	}}.Snapshots())
	if err != nil {
		log.Fatalf("error: %v", err)
	}
}

It outputs this:

"level"=0 "msg"="about to send a POST request to %s with body %s" "<non-string-key: [\"http://localho>"="<no-value>"

Expected behavior

A structured log, something like:

"level"=0 "msg"="about to send a POST request" "url"="http://localhost:9411/api/v2/spans" "body"="..."