github.com/go-logr/logr v1.4.1: funcr.Options

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify github.com/go-logr/logr/funcr.Options in pkg:golang/github.com/go-logr/logr@v1.4.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/go-logr/logr@v1.4.1
Demonstrate these symbols/APIs:
  - github.com/go-logr/logr/funcr.Options

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:4f8eb595d04190f170faec47809e11943fbb7ab99b3f39b93e4eb8e441389ee6","contract":["funcr.New with default Options creates a valid logr.Logger with non-nil LogSink.","funcr.Options Verbosity controls logger.V(level).Enabled() thresholds.","funcr.Options LogTimestamp adds timestamp information to output logs.","funcr.Options LogCaller captures call site caller info in formatted output.","funcr.Options RenderArgsHook allows mutating key-value pairs during rendering.","funcr.NewJSON with funcr.Options formats logs as valid JSON strings to the provided sink function."],"goal":"verify github.com/go-logr/logr/funcr.Options in pkg:golang/github.com/go-logr/logr@v1.4.1","kind":"HOW","packages":["pkg:golang/github.com/go-logr/logr@v1.4.1"],"schemaVersion":1,"symbols":["github.com/go-logr/logr/funcr.Options"]},"contractCommand":["go","test","./..."],"environment":{"arch":"amd64","compiler":"go","compilerVersion":"1.26.6","distro":"ubuntu","ecosystem":"golang","language":"go","languageVersion":"1.26","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","packageManagerVersion":"1.26.6","runtime":"go","runtimeVersion":"1.26.6","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/go-logr/logr@v1.4.1"],"schemaVersion":1,"subject":"pkg:golang/github.com/go-logr/logr@v1.4.1","symbols":["github.com/go-logr/logr/funcr.Options"],"verifierAdapter":"golang@1"}

module sample

go 1.22

require github.com/go-logr/logr v1.4.1

github.com/go-logr/logr v1.4.1 h1:pKouT5E8xu9zeFC39JXRDukb6JFQPXM5p5I91188VAQ=
github.com/go-logr/logr v1.4.1/go.mod h1:9T104GzyrTigFIr8wt5mBrctHMim0Nb2HLGrmQ40KvY=

package sample

import (
	"github.com/go-logr/logr"
	"github.com/go-logr/logr/funcr"
)

// NewFuncLogger creates a logr.Logger using funcr.New with custom Options.
func NewFuncLogger(writeFn func(prefix, args string), opts funcr.Options) logr.Logger {
	return funcr.New(writeFn, opts)
}

// NewJSONFuncLogger creates a logr.Logger using funcr.NewJSON with custom Options.
func NewJSONFuncLogger(writeJSONFn func(obj string), opts funcr.Options) logr.Logger {
	return funcr.NewJSON(writeJSONFn, opts)
}

// BuildOptions constructs a funcr.Options struct with specified settings.
func BuildOptions(verbosity int, logCaller funcr.MessageClass, logTimestamp bool) funcr.Options {
	return funcr.Options{
		Verbosity:    verbosity,
		LogCaller:    logCaller,
		LogTimestamp: logTimestamp,
	}
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/go-logr/logr/funcr.Options in pkg:golang/github.com/go-logr/logr@v1.4.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/go-logr/logr@v1.4.1"
  ],
  "symbols": [
    "github.com/go-logr/logr/funcr.Options"
  ]
}

package test

import (
	"encoding/json"
	"errors"
	"strings"
	"testing"

	"github.com/go-logr/logr"
	"github.com/go-logr/logr/funcr"
	"sample"
)

func TestContract(t *testing.T) {
	// 1. funcr.New with default Options creates a valid logr.Logger with non-nil LogSink.
	var capturedArgs string
	sinkFn := func(_ string, args string) {
		capturedArgs = args
	}
	var defaultLogger logr.Logger = sample.NewFuncLogger(sinkFn, funcr.Options{})
	if defaultLogger.GetSink() == nil {
		t.Fatalf("expected non-nil LogSink from default funcr.New logger")
	}

	// 2. funcr.Options Verbosity controls logger.V(level).Enabled() thresholds.
	optsVerbosity := sample.BuildOptions(2, funcr.None, false)
	vLogger := sample.NewFuncLogger(sinkFn, optsVerbosity)
	if !vLogger.V(0).Enabled() {
		t.Fatalf("expected V(0) to be enabled with Verbosity=2")
	}
	if !vLogger.V(2).Enabled() {
		t.Fatalf("expected V(2) to be enabled with Verbosity=2")
	}
	if vLogger.V(3).Enabled() {
		t.Fatalf("expected V(3) to be disabled with Verbosity=2")
	}

	// Verify logging at disabled level does not invoke write function
	capturedArgs = ""
	vLogger.V(3).Info("should be ignored", "k", "v")
	if capturedArgs != "" {
		t.Fatalf("expected no output for disabled V(3), got %q", capturedArgs)
	}

	// Verify logging at enabled level invokes write function
	vLogger.V(2).Info("enabled message", "key", "val")
	if !strings.Contains(capturedArgs, `"msg"="enabled message"`) || !strings.Contains(capturedArgs, `"key"="val"`) {
		t.Fatalf("expected formatted output containing msg and key, got %q", capturedArgs)
	}

	// 3. funcr.Options LogTimestamp adds timestamp information to output logs.
	var tsOutput string
	tsLogger := sample.NewFuncLogger(func(_ string, args string) {
		tsOutput = args
	}, funcr.Options{
		LogTimestamp: true,
	})
	tsLogger.Info("timestamp test")
	if !strings.Contains(tsOutput, `"ts"=`) {
		t.Fatalf("expected timestamp key 'ts' in output, got %q", tsOutput)
	}

	// 4. funcr.Options LogCaller captures call site caller info in formatted output.
	var callerOutput string
	callerLogger := sample.NewFuncLogger(func(_ string, args string) {
		callerOutput = args
	}, funcr.Options{
		LogCaller: funcr.All,
	})
	callerLogger.Info("caller test")
	if !strings.Contains(callerOutput, `"caller"={"file"=`) {
		t.Fatalf("expected caller info in output, got %q", callerOutput)
	}

	// 5. funcr.Options RenderArgsHook allows mutating key-value pairs during rendering.
	var hookOutput string
	hookLogger := sample.NewFuncLogger(func(_ string, args string) {
		hookOutput = args
	}, funcr.Options{
		RenderArgsHook: func(kvList []any) []any {
			var modified []any
			for i := 0; i < len(kvList); i += 2 {
				key := kvList[i].(string)
				val := kvList[i+1]
				modified = append(modified, "custom_"+key, val)
			}
			return modified
		},
	})
	hookLogger.Info("hook test", "app", "demo")
	if !strings.Contains(hookOutput, `"custom_app"="demo"`) {
		t.Fatalf("expected hook to prefix key with custom_, got %q", hookOutput)
	}

	// 6. funcr.NewJSON with funcr.Options formats logs as valid JSON strings to the provided sink function.
	var jsonOutput string
	jsonLogger := sample.NewJSONFuncLogger(func(obj string) {
		jsonOutput = obj
	}, funcr.Options{
		Verbosity: 1,
	})
	testErr := errors.New("sample error")
	jsonLogger.Error(testErr, "operation failed", "service", "payment", "retry_count", 3)

	var parsed map[string]any
	if err := json.Unmarshal([]byte(jsonOutput), &parsed); err != nil {
		t.Fatalf("expected valid JSON output from NewJSONFuncLogger, got err: %v, raw: %q", err, jsonOutput)
	}
	if parsed["msg"] != "operation failed" {
		t.Fatalf("expected msg 'operation failed', got %v", parsed["msg"])
	}
	if parsed["error"] != "sample error" {
		t.Fatalf("expected error 'sample error', got %v", parsed["error"])
	}
	if parsed["service"] != "payment" {
		t.Fatalf("expected service 'payment', got %v", parsed["service"])
	}
}