go.uber.org/zap v1.28.0: zapcore.EncoderConfig

# zap zapcore.EncoderConfig Verification

## Prior Findings
Search for known solutions for `go.uber.org/zap/zapcore.EncoderConfig` in `pkg:golang/go.uber.org/zap@v1.28.0` returned `NO_SAFE_MATCH`.
Existing samples covered atomic level switching, in-memory observer logging, custom sink registration, and entry metadata, but did not prove `zapcore.EncoderConfig` serialization behaviors and encoder options.

## Pinned Release
- `go.uber.org/zap` pinned to `v1.28.0` via `go.mod` and `go.sum`.

## Observed Behaviour
1. `zapcore.EncoderConfig` customizes JSON field keys (MessageKey, LevelKey, TimeKey, NameKey, CallerKey, StacktraceKey) and completely omits fields when keys are empty strings.
2. `zapcore.EncoderConfig` configures functional primitive encoders (EncodeLevel, EncodeTime, EncodeDuration, EncodeCaller) across both JSON and console formats.
3. `zapcore.EncoderConfig` controls console delimiter spacing with `ConsoleSeparator` and trailing formatting with `LineEnding` / `SkipLineEnding`.

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/zapcore.EncoderConfig 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/zapcore.EncoderConfig

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:sha256:6fb3c906ecf725770b270e3962d0906f8de3cfa4123883fcfa4d48e63d740278","contract":["zapcore.EncoderConfig configures custom JSON key names and omits fields when keys are set to empty.","zapcore.EncoderConfig configures custom level, timestamp, duration, and caller formatting via functional encoders.","zapcore.EncoderConfig configures plain-text console output with custom ConsoleSeparator and line endings."],"goal":"verify go.uber.org/zap/zapcore.EncoderConfig 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/zapcore.EncoderConfig"]},"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/zapcore.EncoderConfig"],"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 (
	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"
)

// BuildCustomJSONEncoderConfig creates an EncoderConfig with custom field keys
// and omits the timestamp field by setting TimeKey to empty.
func BuildCustomJSONEncoderConfig() zapcore.EncoderConfig {
	return zapcore.EncoderConfig{
		MessageKey:     "log_message",
		LevelKey:       "severity",
		TimeKey:        "", // empty key omits timestamp
		NameKey:        "logger_name",
		CallerKey:      "call_site",
		StacktraceKey:  "stack_trace",
		LineEnding:     zapcore.DefaultLineEnding,
		EncodeLevel:    zapcore.CapitalLevelEncoder,
		EncodeDuration: zapcore.StringDurationEncoder,
		EncodeCaller:   zapcore.ShortCallerEncoder,
	}
}

// BuildFormattedJSONEncoderConfig creates an EncoderConfig with functional encoders
// for level, timestamp, duration, and caller formatting.
func BuildFormattedJSONEncoderConfig() zapcore.EncoderConfig {
	return zapcore.EncoderConfig{
		MessageKey:     "msg",
		LevelKey:       "level",
		TimeKey:        "timestamp",
		CallerKey:      "caller",
		EncodeLevel:    zapcore.LowercaseLevelEncoder,
		EncodeTime:     zapcore.RFC3339TimeEncoder,
		EncodeDuration: zapcore.MillisDurationEncoder,
		EncodeCaller:   zapcore.FullCallerEncoder,
		LineEnding:     "\n",
	}
}

// BuildCustomConsoleEncoderConfig creates an EncoderConfig for console output
// configuring custom field separator and line ending.
func BuildCustomConsoleEncoderConfig(separator string, lineEnding string) zapcore.EncoderConfig {
	return zapcore.EncoderConfig{
		MessageKey:       "msg",
		LevelKey:         "level",
		TimeKey:          "ts",
		CallerKey:        "caller",
		ConsoleSeparator: separator,
		LineEnding:       lineEnding,
		EncodeLevel:      zapcore.CapitalLevelEncoder,
		EncodeTime:       zapcore.EpochTimeEncoder,
		EncodeCaller:     zapcore.ShortCallerEncoder,
	}
}

// EncodeJSONEntry encodes an entry and fields using the given EncoderConfig.
func EncodeJSONEntry(cfg zapcore.EncoderConfig, ent zapcore.Entry, fields ...zap.Field) (string, error) {
	enc := zapcore.NewJSONEncoder(cfg)
	buf, err := enc.EncodeEntry(ent, fields)
	if err != nil {
		return "", err
	}
	defer buf.Free()
	return buf.String(), nil
}

// EncodeConsoleEntry encodes an entry and fields into console formatted text.
func EncodeConsoleEntry(cfg zapcore.EncoderConfig, ent zapcore.Entry, fields ...zap.Field) (string, error) {
	enc := zapcore.NewConsoleEncoder(cfg)
	buf, err := enc.EncodeEntry(ent, fields)
	if err != nil {
		return "", err
	}
	defer buf.Free()
	return buf.String(), nil
}

{
  "schemaVersion": 1,
  "goal": "verify go.uber.org/zap/zapcore.EncoderConfig 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/zapcore.EncoderConfig"
  ]
}

package main

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

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

func main() {
	// Contract Assertion 1:
	// zapcore.EncoderConfig configures custom JSON key names and omits fields when keys are set to empty.
	{
		cfg := sample.BuildCustomJSONEncoderConfig()
		ent := zapcore.Entry{
			Level:      zapcore.InfoLevel,
			Time:       time.Date(2026, time.September, 4, 12, 0, 0, 0, time.UTC),
			LoggerName: "auth.service",
			Message:    "token refreshed",
			Caller:     zapcore.NewEntryCaller(101, "/app/auth/handler.go", 42, true),
		}

		out, err := sample.EncodeJSONEntry(cfg, ent,
			zap.String("user_id", "usr-1234"),
			zap.Duration("elapsed", 1500*time.Millisecond),
		)
		if err != nil {
			fmt.Fprintf(os.Stderr, "EncodeJSONEntry 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, "failed to parse json output: %v, raw: %s\n", err, out)
			os.Exit(1)
		}

		if parsed["severity"] != "INFO" {
			fmt.Fprintf(os.Stderr, "expected severity 'INFO', got %v\n", parsed["severity"])
			os.Exit(1)
		}
		if parsed["log_message"] != "token refreshed" {
			fmt.Fprintf(os.Stderr, "expected log_message 'token refreshed', got %v\n", parsed["log_message"])
			os.Exit(1)
		}
		if parsed["logger_name"] != "auth.service" {
			fmt.Fprintf(os.Stderr, "expected logger_name 'auth.service', got %v\n", parsed["logger_name"])
			os.Exit(1)
		}
		if parsed["call_site"] != "auth/handler.go:42" {
			fmt.Fprintf(os.Stderr, "expected call_site 'auth/handler.go:42', got %v\n", parsed["call_site"])
			os.Exit(1)
		}
		if parsed["user_id"] != "usr-1234" {
			fmt.Fprintf(os.Stderr, "expected user_id 'usr-1234', got %v\n", parsed["user_id"])
			os.Exit(1)
		}
		if parsed["elapsed"] != "1.5s" {
			fmt.Fprintf(os.Stderr, "expected elapsed '1.5s', got %v\n", parsed["elapsed"])
			os.Exit(1)
		}

		// Verify that timeKey="" caused the timestamp to be omitted completely
		if _, hasTime := parsed["timestamp"]; hasTime {
			fmt.Fprintf(os.Stderr, "unexpected 'timestamp' key found in JSON\n")
			os.Exit(1)
		}
		if _, hasTs := parsed["ts"]; hasTs {
			fmt.Fprintf(os.Stderr, "unexpected 'ts' key found in JSON\n")
			os.Exit(1)
		}
		if _, hasTimeKey := parsed["time"]; hasTimeKey {
			fmt.Fprintf(os.Stderr, "unexpected 'time' key found in JSON\n")
			os.Exit(1)
		}
	}

	// Contract Assertion 2:
	// zapcore.EncoderConfig configures custom level, timestamp, duration, and caller formatting via functional encoders.
	{
		cfg := sample.BuildFormattedJSONEncoderConfig()
		fixedTime := time.Date(2026, time.September, 4, 15, 30, 0, 0, time.UTC)
		ent := zapcore.Entry{
			Level:   zapcore.WarnLevel,
			Time:    fixedTime,
			Message: "memory threshold approaching",
			Caller:  zapcore.NewEntryCaller(202, "/app/worker/proc.go", 99, true),
		}

		out, err := sample.EncodeJSONEntry(cfg, ent,
			zap.Duration("latency", 250*time.Millisecond),
		)
		if err != nil {
			fmt.Fprintf(os.Stderr, "EncodeJSONEntry 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, "failed to parse json output: %v, raw: %s\n", err, out)
			os.Exit(1)
		}

		if parsed["level"] != "warn" {
			fmt.Fprintf(os.Stderr, "expected level 'warn', got %v\n", parsed["level"])
			os.Exit(1)
		}
		if parsed["timestamp"] != "2026-09-04T15:30:00Z" {
			fmt.Fprintf(os.Stderr, "expected timestamp '2026-09-04T15:30:00Z', got %v\n", parsed["timestamp"])
			os.Exit(1)
		}
		if parsed["caller"] != "/app/worker/proc.go:99" {
			fmt.Fprintf(os.Stderr, "expected full caller '/app/worker/proc.go:99', got %v\n", parsed["caller"])
			os.Exit(1)
		}
		// MillisDurationEncoder serializes 250ms as numeric 250
		lat, ok := parsed["latency"].(float64)
		if !ok || int64(lat) != 250 {
			fmt.Fprintf(os.Stderr, "expected latency 250 (numeric), got %v\n", parsed["latency"])
			os.Exit(1)
		}
	}

	// Contract Assertion 3:
	// zapcore.EncoderConfig configures plain-text console output with custom ConsoleSeparator and line endings.
	{
		separator := " | "
		lineEnding := "\n"
		cfg := sample.BuildCustomConsoleEncoderConfig(separator, lineEnding)

		ent := zapcore.Entry{
			Level:   zapcore.ErrorLevel,
			Time:    time.Unix(1700000000, 0),
			Message: "database connection failed",
			Caller:  zapcore.NewEntryCaller(303, "/app/db/conn.go", 55, true),
		}

		out, err := sample.EncodeConsoleEntry(cfg, ent,
			zap.String("db", "primary"),
		)
		if err != nil {
			fmt.Fprintf(os.Stderr, "EncodeConsoleEntry failed: %v\n", err)
			os.Exit(1)
		}

		if !strings.HasSuffix(out, lineEnding) {
			fmt.Fprintf(os.Stderr, "expected console output to end with newline, got %q\n", out)
			os.Exit(1)
		}

		// Verify ConsoleSeparator delimiters
		if !strings.Contains(out, " | ERROR | ") {
			fmt.Fprintf(os.Stderr, "expected ' | ERROR | ' in console output, got %q\n", out)
			os.Exit(1)
		}
		if !strings.Contains(out, " | db/conn.go:55 | ") {
			fmt.Fprintf(os.Stderr, "expected ' | db/conn.go:55 | ' in console output, got %q\n", out)
			os.Exit(1)
		}
		if !strings.Contains(out, "database connection failed") {
			fmt.Fprintf(os.Stderr, "expected message in console output, got %q\n", out)
			os.Exit(1)
		}
		if !strings.Contains(out, `{"db": "primary"}`) {
			fmt.Fprintf(os.Stderr, "expected JSON context in console output, got %q\n", out)
			os.Exit(1)
		}
	}

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