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

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.Fields 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.Fields

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:c3de97f3a459b2f162577878d7917174826acb4d077cacc4eb73d637dd0dab26","contract":["Fields map sets structured contextual fields on a log Entry via WithFields","WithFields chains incrementally merging subsequent Fields and overwriting existing keys","Entry Data property preserves all key-value pairs assigned through Fields","JSONFormatter encodes all Fields into key-value JSON properties in log output"],"goal":"verify github.com/sirupsen/logrus.Fields 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.Fields"]},"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.Fields"],"verifierAdapter":"golang@1"}

package sample

import (
	"bytes"

	"github.com/sirupsen/logrus"
)

// LogWithFields creates a log entry with the provided Fields and returns it.
func LogWithFields(logger *logrus.Logger, fields logrus.Fields) *logrus.Entry {
	if logger == nil {
		logger = logrus.New()
	}
	return logger.WithFields(fields)
}

// MergeFields chains additional fields into an existing Entry.
func MergeFields(entry *logrus.Entry, extra logrus.Fields) *logrus.Entry {
	return entry.WithFields(extra)
}

// FormatJSON writes log output formatted with JSONFormatter into a buffer.
func FormatJSON(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
}

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.Fields 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.Fields"
  ]
}

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.Fields...")

	// Assertion 1: Fields map sets structured contextual fields on a log Entry via WithFields
	{
		f := logrus.Fields{
			"app":     "test-service",
			"attempt": 1,
			"active":  true,
		}

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

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

		if entry.Data["app"] != "test-service" || entry.Data["attempt"] != 1 || entry.Data["active"] != true {
			fmt.Fprintf(os.Stderr, "Assertion 1 failed: entry.Data mismatch: %v\n", entry.Data)
			os.Exit(1)
		}
		fmt.Println("  ✓ Assertion 1 passed: Fields sets structured contextual fields via WithFields")
	}

	// Assertion 2: WithFields chains incrementally merging subsequent Fields and overwriting existing keys
	{
		logger := logrus.New()
		var buf bytes.Buffer
		logger.SetOutput(&buf)

		baseFields := logrus.Fields{
			"service": "auth",
			"status":  "pending",
			"count":   10,
		}
		entry1 := logger.WithFields(baseFields)

		overrideFields := logrus.Fields{
			"status": "completed", // overwrites pending
			"worker": 4,           // new field
		}
		entry2 := sample.MergeFields(entry1, overrideFields)

		if entry2.Data["service"] != "auth" {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: service field lost\n")
			os.Exit(1)
		}
		if entry2.Data["status"] != "completed" {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: status field not overwritten: %v\n", entry2.Data["status"])
			os.Exit(1)
		}
		if entry2.Data["worker"] != 4 {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: worker field missing\n")
			os.Exit(1)
		}
		if entry2.Data["count"] != 10 {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: count field lost\n")
			os.Exit(1)
		}
		// Ensure entry1 was not mutated (immutability of entry data chaining)
		if entry1.Data["status"] != "pending" {
			fmt.Fprintf(os.Stderr, "Assertion 2 failed: entry1 mutated\n")
			os.Exit(1)
		}
		fmt.Println("  ✓ Assertion 2 passed: WithFields chains and merges subsequent Fields with overwrite")
	}

	// Assertion 3: Entry Data property preserves all key-value pairs assigned through Fields
	{
		complexFields := logrus.Fields{
			"string_val": "hello",
			"int_val":    42,
			"float_val":  3.14,
			"bool_val":   false,
			"slice_val":  []string{"a", "b", "c"},
		}

		entry := logrus.WithFields(complexFields)
		if entry.Data["string_val"] != "hello" {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed: string_val mismatch\n")
			os.Exit(1)
		}
		if entry.Data["int_val"] != 42 {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed: int_val mismatch\n")
			os.Exit(1)
		}
		if entry.Data["float_val"] != 3.14 {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed: float_val mismatch\n")
			os.Exit(1)
		}
		if entry.Data["bool_val"] != false {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed: bool_val mismatch\n")
			os.Exit(1)
		}
		sliceVal, ok := entry.Data["slice_val"].([]string)
		if !ok || len(sliceVal) != 3 || sliceVal[0] != "a" {
			fmt.Fprintf(os.Stderr, "Assertion 3 failed: slice_val mismatch\n")
			os.Exit(1)
		}
		fmt.Println("  ✓ Assertion 3 passed: Entry Data property preserves all types assigned through Fields")
	}

	// Assertion 4: JSONFormatter encodes all Fields into key-value JSON properties in log output
	{
		testFields := logrus.Fields{
			"component":  "database",
			"latency_ms": 150,
			"successful": true,
		}
		out, err := sample.FormatJSON(testFields, "query executed")
		if err != nil {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: %v\n", err)
			os.Exit(1)
		}

		var parsed map[string]interface{}
		if err := json.Unmarshal([]byte(out), &parsed); err != nil {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed to parse JSON output: %v\nOutput: %s\n", err, out)
			os.Exit(1)
		}

		if parsed["component"] != "database" {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: JSON missing component field\n")
			os.Exit(1)
		}
		if parsed["latency_ms"] != float64(150) {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: JSON latency_ms mismatch: %v\n", parsed["latency_ms"])
			os.Exit(1)
		}
		if parsed["successful"] != true {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: JSON successful field mismatch\n")
			os.Exit(1)
		}
		if parsed["msg"] != "query executed" {
			fmt.Fprintf(os.Stderr, "Assertion 4 failed: JSON msg mismatch\n")
			os.Exit(1)
		}
		fmt.Println("  ✓ Assertion 4 passed: JSONFormatter encodes Fields into structured JSON output")
	}

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