github.com/sirupsen/logrus v1.4.2: FieldMap

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/sirupsen/logrus.FieldMap in pkg:golang/github.com/sirupsen/logrus@v1.4.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/sirupsen/logrus@v1.4.2
Demonstrate these symbols/APIs:
  - github.com/sirupsen/logrus.FieldMap

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:c42ae291dfbeb2df0541075c2ff644d03e44ec8abd287891a57855b0a4b3bfa8","contract":["FieldMap customizes standard field keys including time, level, and message in JSONFormatter output","FieldMap customizes standard field keys in TextFormatter output","FieldMap retains default field key names for unmapped standard fields","FieldMap prefixes user fields with fields. when they clash with remapped keys","FieldMap customizes error field key name FieldKeyLogrusError in JSONFormatter output"],"goal":"verify github.com/sirupsen/logrus.FieldMap in pkg:golang/github.com/sirupsen/logrus@v1.4.2","kind":"HOW","packages":["pkg:golang/github.com/sirupsen/logrus@v1.4.2"],"schemaVersion":1,"symbols":["github.com/sirupsen/logrus.FieldMap"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/sirupsen/logrus@v1.4.2"],"schemaVersion":1,"subject":"pkg:golang/github.com/sirupsen/logrus@v1.4.2","symbols":["github.com/sirupsen/logrus.FieldMap"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/sirupsen/logrus v1.4.2

require (
	github.com/konsorten/go-windows-terminal-sequences v1.0.1 // indirect
	golang.org/x/sys v0.0.0-20190422165155-953cdadca894 // indirect
)

github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/konsorten/go-windows-terminal-sequences v1.0.1 h1:mweAR1A6xJ3oS2pRaGiHgQ4OO8tzTaLawm8vnODuwDk=
github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/sirupsen/logrus v1.4.2 h1:SPIRibHv4MatM3XXNO2BJeFLZwZ2LvZgfQ5+UNI2im4=
github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=
github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
golang.org/x/sys v0.0.0-20190422165155-953cdadca894 h1:Cz4ceDQGXuKRnVBDTS23GTn/pU5OE2C0WrNTOYK1Uuc=
golang.org/x/sys v0.0.0-20190422165155-953cdadca894/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

package main

import (
	"bytes"
	"fmt"
	"os"

	"github.com/sirupsen/logrus"
)

func main() {
	logger := logrus.New()
	var buf bytes.Buffer
	logger.SetOutput(&buf)

	// Configure JSONFormatter with a custom FieldMap
	logger.SetFormatter(&logrus.JSONFormatter{
		FieldMap: logrus.FieldMap{
			logrus.FieldKeyTime:  "@timestamp",
			logrus.FieldKeyLevel: "severity",
			logrus.FieldKeyMsg:   "message",
		},
	})

	logger.WithField("component", "worker").Info("service worker started")
	fmt.Print(buf.String())

	// Configure TextFormatter with a custom FieldMap
	buf.Reset()
	logger.SetFormatter(&logrus.TextFormatter{
		DisableColors: true,
		FieldMap: logrus.FieldMap{
			logrus.FieldKeyTime:  "timestamp",
			logrus.FieldKeyLevel: "log_level",
			logrus.FieldKeyMsg:   "text",
		},
	})

	logger.WithField("status", "ok").Info("healthcheck completed")
	fmt.Print(buf.String())

	if _, err := os.Stdout.WriteString("logrus.FieldMap demonstration complete.\n"); err != nil {
		os.Exit(1)
	}
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/sirupsen/logrus.FieldMap in pkg:golang/github.com/sirupsen/logrus@v1.4.2",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/sirupsen/logrus@v1.4.2"
  ],
  "symbols": [
    "github.com/sirupsen/logrus.FieldMap"
  ]
}

package main

import (
	"encoding/json"
	"fmt"
	"os"
	"strings"
	"time"

	"github.com/sirupsen/logrus"
)

func main() {
	// Assertion 1: FieldMap customizes standard field keys including time, level, and message in JSONFormatter output
	{
		formatter := &logrus.JSONFormatter{
			FieldMap: logrus.FieldMap{
				logrus.FieldKeyTime:  "@timestamp",
				logrus.FieldKeyLevel: "severity",
				logrus.FieldKeyMsg:   "message",
			},
		}

		fixedTime := time.Date(2026, 5, 12, 10, 0, 0, 0, time.UTC)
		entry := &logrus.Entry{
			Logger:  logrus.New(),
			Time:    fixedTime,
			Level:   logrus.InfoLevel,
			Message: "contract testing message",
			Data:    logrus.Fields{},
		}

		bytes, err := formatter.Format(entry)
		if err != nil {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: Format error: %v\n", err)
			os.Exit(1)
		}

		var parsed map[string]interface{}
		if err := json.Unmarshal(bytes, &parsed); err != nil {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: JSON unmarshal error: %v\n", err)
			os.Exit(1)
		}

		if parsed["@timestamp"] == nil || parsed["severity"] != "info" || parsed["message"] != "contract testing message" {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: remapped keys missing or mismatch in parsed output: %v\n", parsed)
			os.Exit(1)
		}

		if _, exists := parsed["time"]; exists {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: default 'time' key was not remapped\n")
			os.Exit(1)
		}
		if _, exists := parsed["level"]; exists {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: default 'level' key was not remapped\n")
			os.Exit(1)
		}
		if _, exists := parsed["msg"]; exists {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: default 'msg' key was not remapped\n")
			os.Exit(1)
		}
	}

	// Assertion 2: FieldMap customizes standard field keys in TextFormatter output
	{
		formatter := &logrus.TextFormatter{
			DisableColors: true,
			FieldMap: logrus.FieldMap{
				logrus.FieldKeyTime:  "event_time",
				logrus.FieldKeyLevel: "severity",
				logrus.FieldKeyMsg:   "payload",
			},
		}

		fixedTime := time.Date(2026, 5, 12, 10, 0, 0, 0, time.UTC)
		entry := &logrus.Entry{
			Logger:  logrus.New(),
			Time:    fixedTime,
			Level:   logrus.WarnLevel,
			Message: "warning payload message",
			Data:    logrus.Fields{},
		}

		bytes, err := formatter.Format(entry)
		if err != nil {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: Format error: %v\n", err)
			os.Exit(1)
		}

		out := string(bytes)
		if !strings.Contains(out, "event_time=") || !strings.Contains(out, "severity=warning") || !strings.Contains(out, `payload="warning payload message"`) {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: text output missing remapped field keys: %s\n", out)
			os.Exit(1)
		}

		if strings.Contains(out, "level=warning") || strings.Contains(out, `msg="warning payload message"`) {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: text output still contains original keys: %s\n", out)
			os.Exit(1)
		}
	}

	// Assertion 3: FieldMap retains default field key names for unmapped standard fields
	{
		formatter := &logrus.JSONFormatter{
			FieldMap: logrus.FieldMap{
				logrus.FieldKeyMsg: "custom_msg",
			},
		}

		entry := &logrus.Entry{
			Logger:  logrus.New(),
			Time:    time.Date(2026, 5, 12, 10, 0, 0, 0, time.UTC),
			Level:   logrus.ErrorLevel,
			Message: "error message",
			Data:    logrus.Fields{},
		}

		bytes, err := formatter.Format(entry)
		if err != nil {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: Format error: %v\n", err)
			os.Exit(1)
		}

		var parsed map[string]interface{}
		if err := json.Unmarshal(bytes, &parsed); err != nil {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: JSON unmarshal error: %v\n", err)
			os.Exit(1)
		}

		if parsed["custom_msg"] != "error message" {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: expected 'custom_msg' in output, got: %v\n", parsed)
			os.Exit(1)
		}
		if parsed["level"] != "error" {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: unmapped 'level' key should retain default name: %v\n", parsed)
			os.Exit(1)
		}
		if parsed["time"] == nil {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: unmapped 'time' key should retain default name: %v\n", parsed)
			os.Exit(1)
		}
		if _, exists := parsed["msg"]; exists {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: remapped 'msg' should not appear under default name: %v\n", parsed)
			os.Exit(1)
		}
	}

	// Assertion 4: FieldMap prefixes user fields with fields. when they clash with remapped keys
	{
		formatter := &logrus.JSONFormatter{
			FieldMap: logrus.FieldMap{
				logrus.FieldKeyMsg: "message",
			},
		}

		entry := &logrus.Entry{
			Logger:  logrus.New(),
			Time:    time.Date(2026, 5, 12, 10, 0, 0, 0, time.UTC),
			Level:   logrus.InfoLevel,
			Message: "main message",
			Data: logrus.Fields{
				"message": "user provided message field",
			},
		}

		bytes, err := formatter.Format(entry)
		if err != nil {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: Format error: %v\n", err)
			os.Exit(1)
		}

		var parsed map[string]interface{}
		if err := json.Unmarshal(bytes, &parsed); err != nil {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: JSON unmarshal error: %v\n", err)
			os.Exit(1)
		}

		if parsed["message"] != "main message" {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: expected remapped message field to contain entry message: %v\n", parsed)
			os.Exit(1)
		}
		if parsed["fields.message"] != "user provided message field" {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: expected clashing field to be prefixed with 'fields.': %v\n", parsed)
			os.Exit(1)
		}
	}

	// Assertion 5: FieldMap customizes error field key name FieldKeyLogrusError in JSONFormatter output
	{
		formatter := &logrus.JSONFormatter{
			FieldMap: logrus.FieldMap{
				logrus.FieldKeyLogrusError: "internal_error",
			},
		}

		logger := logrus.New()
		entry := logger.WithField("invalid_func", func() {})
		entry.Time = time.Date(2026, 5, 12, 10, 0, 0, 0, time.UTC)
		entry.Message = "error test entry"

		bytes, err := formatter.Format(entry)
		if err != nil {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: Format error: %v\n", err)
			os.Exit(1)
		}

		var parsed map[string]interface{}
		if err := json.Unmarshal(bytes, &parsed); err != nil {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: JSON unmarshal error: %v\n", err)
			os.Exit(1)
		}

		if parsed["internal_error"] != `can not add field "invalid_func"` {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: expected 'internal_error' field with validation message in output, got: %v\n", parsed)
			os.Exit(1)
		}
		if _, exists := parsed["logrus_error"]; exists {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: default 'logrus_error' key was not remapped: %v\n", parsed)
			os.Exit(1)
		}
	}

	fmt.Println("All FieldMap contract assertions passed successfully.")
}