go.uber.org/zap v1.28.0: String

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 go.uber.org/zap.String in pkg:golang/go.uber.org/zap@v1.28.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/go.uber.org/zap@v1.28.0
Demonstrate these symbols/APIs:
  - go.uber.org/zap.String

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:sha256:56a779ed169c011772ede540e805f71d92329538486527cb3b38a42e3e390e8f","contract":["NewStringField constructs a zap.Field with StringType, key, and string value","LogWithStringField logs an info-level message with a zap.String structured field to a JSON buffer","WithStringField derives a child logger with a preset zap.String context field"],"goal":"verify go.uber.org/zap.String in pkg:golang/go.uber.org/zap@v1.28.0","kind":"HOW","packages":["pkg:golang/go.uber.org/zap@v1.28.0"],"schemaVersion":1,"symbols":["go.uber.org/zap.String"]},"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/go.uber.org/zap@v1.28.0"],"schemaVersion":1,"subject":"pkg:golang/go.uber.org/zap@v1.28.0","symbols":["go.uber.org/zap.String"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.22.0

require go.uber.org/zap v1.28.0

require go.uber.org/multierr v1.10.0 // 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/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
go.uber.org/multierr v1.10.0 h1:S0h4aNzvfcFsC3dRF1jLoaov7oRaKqRGC/pUEJ2yvPQ=
go.uber.org/multierr v1.10.0/go.mod h1:20+QtiLqy0Nd6FdQB9TLXag12DsQkrbs3htMFfDN80Y=
go.uber.org/zap v1.28.0 h1:IZzaP1Fv73/T/pBMLk4VutPl36uNC+OSUh3JLG3FIjo=
go.uber.org/zap v1.28.0/go.mod h1:rDLpOi171uODNm/mxFcuYWxDsqWSAVkFdX4XojSKg/Q=
go.yaml.in/yaml/v3 v3.0.4 h1:tfq32ie2Jv2UxXFdLJdh3jXuOzWiL1fo0bu/FbuKpbc=
go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package sample

import (
	"bytes"

	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"
)

// CreateJSONBufferLogger creates a zap.Logger configured with a JSON encoder writing to an in-memory buffer.
func CreateJSONBufferLogger(buf *bytes.Buffer) *zap.Logger {
	encoderCfg := zapcore.EncoderConfig{
		MessageKey:     "msg",
		LevelKey:       "level",
		NameKey:        "logger",
		EncodeLevel:    zapcore.LowercaseLevelEncoder,
		EncodeTime:     zapcore.ISO8601TimeEncoder,
		EncodeDuration: zapcore.StringDurationEncoder,
	}
	core := zapcore.NewCore(
		zapcore.NewJSONEncoder(encoderCfg),
		zapcore.AddSync(buf),
		zapcore.InfoLevel,
	)
	return zap.New(core)
}

// NewStringField creates a zap.Field using zap.String with the given key and value.
func NewStringField(key string, val string) zap.Field {
	return zap.String(key, val)
}

// LogWithStringField logs an info-level message with a zap.String structured field.
func LogWithStringField(logger *zap.Logger, msg string, key string, val string) {
	if logger != nil {
		logger.Info(msg, zap.String(key, val))
	}
}

// WithStringField derives a child logger with a preset zap.String context field.
func WithStringField(logger *zap.Logger, key string, val string) *zap.Logger {
	if logger == nil {
		return nil
	}
	return logger.With(zap.String(key, val))
}

{
  "schemaVersion": 1,
  "goal": "verify go.uber.org/zap.String in pkg:golang/go.uber.org/zap@v1.28.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/go.uber.org/zap@v1.28.0"
  ],
  "symbols": [
    "go.uber.org/zap.String"
  ]
}

package main

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

	"example.com/sample"
	"go.uber.org/zap/zapcore"
)

type logEntry struct {
	Level   string `json:"level"`
	Msg     string `json:"msg"`
	Service string `json:"service,omitempty"`
	Env     string `json:"env,omitempty"`
}

func main() {
	// 1. Verify NewStringField constructs a zap.Field with StringType, key, and value
	f := sample.NewStringField("service", "billing")
	if f.Key != "service" {
		fmt.Fprintf(os.Stderr, "expected field key 'service', got %q\n", f.Key)
		os.Exit(1)
	}
	if f.String != "billing" {
		fmt.Fprintf(os.Stderr, "expected field string 'billing', got %q\n", f.String)
		os.Exit(1)
	}
	if f.Type != zapcore.StringType {
		fmt.Fprintf(os.Stderr, "expected field type StringType, got %v\n", f.Type)
		os.Exit(1)
	}

	// 2. Verify LogWithStringField writes expected JSON structured log
	var buf bytes.Buffer
	logger := sample.CreateJSONBufferLogger(&buf)
	if logger == nil {
		fmt.Fprintf(os.Stderr, "expected non-nil logger\n")
		os.Exit(1)
	}

	sample.LogWithStringField(logger, "server starting", "service", "billing")

	var entry logEntry
	if err := json.Unmarshal(buf.Bytes(), &entry); err != nil {
		fmt.Fprintf(os.Stderr, "failed to parse log JSON: %v, raw: %s\n", err, buf.String())
		os.Exit(1)
	}

	if entry.Level != "info" {
		fmt.Fprintf(os.Stderr, "expected level 'info', got %q\n", entry.Level)
		os.Exit(1)
	}
	if entry.Msg != "server starting" {
		fmt.Fprintf(os.Stderr, "expected msg 'server starting', got %q\n", entry.Msg)
		os.Exit(1)
	}
	if entry.Service != "billing" {
		fmt.Fprintf(os.Stderr, "expected service 'billing', got %q\n", entry.Service)
		os.Exit(1)
	}

	// 3. Verify WithStringField derives child logger carrying the zap.String field
	buf.Reset()
	child := sample.WithStringField(logger, "env", "production")
	if child == nil {
		fmt.Fprintf(os.Stderr, "expected non-nil child logger\n")
		os.Exit(1)
	}

	sample.LogWithStringField(child, "worker active", "service", "payment")

	var childEntry logEntry
	if err := json.Unmarshal(buf.Bytes(), &childEntry); err != nil {
		fmt.Fprintf(os.Stderr, "failed to parse child log JSON: %v, raw: %s\n", err, buf.String())
		os.Exit(1)
	}

	if childEntry.Level != "info" {
		fmt.Fprintf(os.Stderr, "expected child level 'info', got %q\n", childEntry.Level)
		os.Exit(1)
	}
	if childEntry.Msg != "worker active" {
		fmt.Fprintf(os.Stderr, "expected child msg 'worker active', got %q\n", childEntry.Msg)
		os.Exit(1)
	}
	if childEntry.Env != "production" {
		fmt.Fprintf(os.Stderr, "expected child env 'production', got %q\n", childEntry.Env)
		os.Exit(1)
	}
	if childEntry.Service != "payment" {
		fmt.Fprintf(os.Stderr, "expected child service 'payment', got %q\n", childEntry.Service)
		os.Exit(1)
	}

	fmt.Println("All contracts passed successfully.")
}