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

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.WithFields 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.WithFields

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:dd54a89ec20ae7c34d203b323cbc640b5b0ecb7f0d69f9256fb30a0d15f1fd49","contract":["WithFields creates an Entry containing the specified fields map","WithFields chains multiple field sets and overwrites matching keys","WithFields leaves the original Entry unmodified when chaining new fields","JSONFormatter serializes fields added by WithFields into structured output"],"goal":"verify github.com/sirupsen/logrus.WithFields 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.WithFields"]},"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.WithFields"],"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=

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

package main

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

	"github.com/sirupsen/logrus"
	"sample"
)

func main() {
	fmt.Println("Running contract tests for github.com/sirupsen/logrus.WithFields...")

	// Assertion 1: WithFields creates an Entry containing the specified fields map
	{
		fields := logrus.Fields{
			"environment": "production",
			"worker_id":   42,
			"enabled":     true,
		}

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

		entry := sample.WithFields(logger, fields)
		if entry == nil {
			fmt.Fprintf(os.Stderr, "Assertion 1 failed: entry is nil\n")
			os.Exit(1)
		}

		if entry.Data["environment"] != "production" || entry.Data["worker_id"] != 42 || entry.Data["enabled"] != true {
			fmt.Fprintf(os.Stderr, "Assertion 1 failed: entry.Data mismatch: %v\n", entry.Data)
			os.Exit(1)
		}

		// Also verify package-level logrus.WithFields
		stdEntry := sample.WithFields(nil, fields)
		if stdEntry == nil || stdEntry.Data["environment"] != "production" {
			fmt.Fprintf(os.Stderr, "Assertion 1 failed: standard entry mismatch\n")
			os.Exit(1)
		}

		fmt.Println("  ✓ Assertion 1 passed: WithFields creates an Entry containing the specified fields map")
	}

	// Assertion 2: WithFields chains multiple field sets and overwrites matching keys
	{
		logger := logrus.New()
		initialFields := logrus.Fields{
			"service": "billing",
			"status":  "pending",
			"retries": 0,
		}
		entry1 := logger.WithFields(initialFields)

		overrideFields := logrus.Fields{
			"status": "success",
			"action": "charge",
		}
		entry2 := sample.ChainFields(entry1, overrideFields)

		if entry2.Data["service"] != "billing" {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: service field missing: %v\n", entry2.Data)
			os.Exit(1)
		}
		if entry2.Data["status"] != "success" {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: status was not overwritten: %v\n", entry2.Data["status"])
			os.Exit(1)
		}
		if entry2.Data["action"] != "charge" {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: action field missing: %v\n", entry2.Data)
			os.Exit(1)
		}
		if entry2.Data["retries"] != 0 {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: retries field missing: %v\n", entry2.Data)
			os.Exit(1)
		}

		fmt.Println("  ✓ Assertion 2 passed: WithFields chains multiple field sets and overwrites matching keys")
	}

	// Assertion 3: WithFields leaves the original Entry unmodified when chaining new fields
	{
		logger := logrus.New()
		baseFields := logrus.Fields{
			"request_id": "req-123",
			"version":    1,
		}
		baseEntry := logger.WithFields(baseFields)

		_ = sample.ChainFields(baseEntry, logrus.Fields{
			"version": 2,
			"extra":   "value",
		})

		if baseEntry.Data["version"] != 1 {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed: baseEntry.Data['version'] mutated to: %v\n", baseEntry.Data["version"])
			os.Exit(1)
		}
		if _, exists := baseEntry.Data["extra"]; exists {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed: baseEntry.Data has extra field\n")
			os.Exit(1)
		}

		fmt.Println("  ✓ Assertion 3 passed: WithFields leaves the original Entry unmodified when chaining new fields")
	}

	// Assertion 4: JSONFormatter serializes fields added by WithFields into structured output
	{
		fields := logrus.Fields{
			"component": "auth-service",
			"user_id":   1001,
			"success":   true,
		}

		output, err := sample.LogWithFormatter(fields, "user logged in")
		if err != nil {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed with error: %v\n", err)
			os.Exit(1)
		}

		var parsed map[string]interface{}
		if err := json.Unmarshal([]byte(output), &parsed); err != nil {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: cannot parse JSON output: %v\nRaw: %s\n", err, output)
			os.Exit(1)
		}

		if parsed["component"] != "auth-service" {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: component field mismatch in JSON: %v\n", parsed["component"])
			os.Exit(1)
		}
		if parsed["user_id"] != float64(1001) {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: user_id mismatch in JSON: %v\n", parsed["user_id"])
			os.Exit(1)
		}
		if parsed["success"] != true {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: success mismatch in JSON: %v\n", parsed["success"])
			os.Exit(1)
		}
		if parsed["msg"] != "user logged in" {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: msg mismatch in JSON: %v\n", parsed["msg"])
			os.Exit(1)
		}

		fmt.Println("  ✓ Assertion 4 passed: JSONFormatter serializes fields added by WithFields into structured output")
	}

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

package sample

import (
	"bytes"

	"github.com/sirupsen/logrus"
)

// WithFields creates a new log Entry with the specified Fields using the given logger.
// If logger is nil, the package-level logrus.WithFields is used.
func WithFields(logger *logrus.Logger, fields logrus.Fields) *logrus.Entry {
	if logger == nil {
		return logrus.WithFields(fields)
	}
	return logger.WithFields(fields)
}

// ChainFields adds more fields to an existing Entry and returns the new Entry.
func ChainFields(entry *logrus.Entry, fields logrus.Fields) *logrus.Entry {
	return entry.WithFields(fields)
}

// LogWithFormatter writes a log entry with fields formatted as JSON to a string.
func LogWithFormatter(fields logrus.Fields, msg string) (string, error) {
	var buf bytes.Buffer
	logger := logrus.New()
	logger.SetOutput(&buf)
	logger.SetFormatter(&logrus.JSONFormatter{})
	logger.WithFields(fields).Info(msg)
	return buf.String(), nil
}