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

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.FieldKeyMsg 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.FieldKeyMsg

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:sha256:2d87f2e16f82240fe13cbdcc059e8458c6a8974f9a50d6bbabae90bd9fbbe10a","contract":["logrus.FieldKeyMsg constant equals default message key msg","logrus.JSONFormatter outputs the log message under logrus.FieldKeyMsg by default","logrus.JSONFormatter customizes the message key using FieldMap with logrus.FieldKeyMsg","logrus.TextFormatter customizes the message key using FieldMap with logrus.FieldKeyMsg"],"goal":"verify github.com/sirupsen/logrus.FieldKeyMsg 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.FieldKeyMsg"]},"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.FieldKeyMsg"],"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() {
	fmt.Printf("Default logrus message field key: %s\n", logrus.FieldKeyMsg)

	// Demonstration 1: Default JSON format uses FieldKeyMsg ("msg")
	logger := logrus.New()
	logger.SetOutput(os.Stdout)
	logger.SetFormatter(&logrus.JSONFormatter{
		DisableTimestamp: true,
	})
	logger.Info("Demonstrating default log message")

	// Demonstration 2: Customizing the message key with FieldMap and FieldKeyMsg
	customLogger := logrus.New()
	var buf bytes.Buffer
	customLogger.SetOutput(&buf)
	customLogger.SetFormatter(&logrus.JSONFormatter{
		DisableTimestamp: true,
		FieldMap: logrus.FieldMap{
			logrus.FieldKeyMsg: "custom_message",
		},
	})
	customLogger.Info("Demonstrating customized message key")
	fmt.Printf("Custom JSON output: %s", buf.String())

	// Demonstration 3: Customizing the message key in TextFormatter
	buf.Reset()
	customLogger.SetFormatter(&logrus.TextFormatter{
		DisableColors:    true,
		DisableTimestamp: true,
		FieldMap: logrus.FieldMap{
			logrus.FieldKeyMsg: "custom_message",
		},
	})
	customLogger.Info("Demonstrating customized text message key")
	fmt.Printf("Custom Text output: %s", buf.String())
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/sirupsen/logrus.FieldKeyMsg 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.FieldKeyMsg"
  ]
}

package main

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

	"github.com/sirupsen/logrus"
)

func main() {
	// Assertion 1: logrus.FieldKeyMsg constant equals default message key msg
	if logrus.FieldKeyMsg != "msg" {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: expected FieldKeyMsg to be %q, got %q\n", "msg", logrus.FieldKeyMsg)
		os.Exit(1)
	}

	// Assertion 2: logrus.JSONFormatter outputs the log message under logrus.FieldKeyMsg by default
	{
		var buf bytes.Buffer
		logger := logrus.New()
		logger.SetOutput(&buf)
		logger.SetFormatter(&logrus.JSONFormatter{
			DisableTimestamp: true,
		})

		testMsg := "default json log message"
		logger.Info(testMsg)

		var data map[string]interface{}
		if err := json.Unmarshal(buf.Bytes(), &data); err != nil {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: invalid JSON output: %v\n", err)
			os.Exit(1)
		}

		val, ok := data[logrus.FieldKeyMsg]
		if !ok || val != testMsg {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: expected key %q with value %q, got %v\n", logrus.FieldKeyMsg, testMsg, val)
			os.Exit(1)
		}
	}

	// Assertion 3: logrus.JSONFormatter customizes the message key using FieldMap with logrus.FieldKeyMsg
	{
		var buf bytes.Buffer
		logger := logrus.New()
		logger.SetOutput(&buf)
		customKey := "custom_message"
		logger.SetFormatter(&logrus.JSONFormatter{
			DisableTimestamp: true,
			FieldMap: logrus.FieldMap{
				logrus.FieldKeyMsg: customKey,
			},
		})

		testMsg := "custom key json log message"
		logger.Info(testMsg)

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

		if _, exists := data[logrus.FieldKeyMsg]; exists {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: default key %q should have been replaced\n", logrus.FieldKeyMsg)
			os.Exit(1)
		}

		val, ok := data[customKey]
		if !ok || val != testMsg {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: expected custom key %q with value %q, got %v\n", customKey, testMsg, val)
			os.Exit(1)
		}
	}

	// Assertion 4: logrus.TextFormatter customizes the message key using FieldMap with logrus.FieldKeyMsg
	{
		var buf bytes.Buffer
		logger := logrus.New()
		logger.SetOutput(&buf)
		customKey := "custom_message"
		logger.SetFormatter(&logrus.TextFormatter{
			DisableColors:    true,
			DisableTimestamp: true,
			FieldMap: logrus.FieldMap{
				logrus.FieldKeyMsg: customKey,
			},
		})

		testMsg := "custom text message"
		logger.Info(testMsg)

		output := buf.String()
		expectedSubstring := fmt.Sprintf("%s=%q", customKey, testMsg)
		defaultSubstring := fmt.Sprintf("%s=", logrus.FieldKeyMsg)

		if !strings.Contains(output, expectedSubstring) {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: expected output to contain %q, got %q\n", expectedSubstring, output)
			os.Exit(1)
		}
		if strings.Contains(output, defaultSubstring) {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: output should not contain default key %q, got %q\n", defaultSubstring, output)
			os.Exit(1)
		}
	}

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