github.com/go-kit/log v0.1.0: level.AllowInfo

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/go-kit/log/level.AllowInfo in pkg:golang/github.com/go-kit/log@v0.1.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/go-kit/log@v0.1.0
Demonstrate these symbols/APIs:
  - github.com/go-kit/log/level.AllowInfo
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

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:sha256:4d7b45c33b67b5cc41821eb92e086ae38af939da85095707dbcc9f6387a5dcbf","contract":["AllowInfo allows error, warn, and info level log events to pass through to the underlying logger","AllowInfo squelches debug level log events by default without returning an error","AllowInfo passes non-leveled log events through unmodified by default","AllowInfo returns ErrNotAllowed when a disallowed debug log event is squelched","AllowInfo with SquelchNoLevel squelches log events that lack a level","AllowInfo works with contextual loggers created via log.With and log.NewLogfmtLogger"],"goal":"verify github.com/go-kit/log/level.AllowInfo in pkg:golang/github.com/go-kit/log@v0.1.0","kind":"HOW","packages":["pkg:golang/github.com/go-kit/log@v0.1.0"],"schemaVersion":1,"symbols":["github.com/go-kit/log/level.AllowInfo"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","language":"go","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/go-kit/log@v0.1.0"],"schemaVersion":1,"subject":"pkg:golang/github.com/go-kit/log@v0.1.0","symbols":["github.com/go-kit/log/level.AllowInfo"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/go-kit/log v0.1.0

require github.com/go-logfmt/logfmt v0.5.0 // indirect

github.com/go-kit/log v0.1.0 h1:DGJh0Sm43HbOeYDNnVZFl8BvcYVvjD5bqYJvp0REbwQ=
github.com/go-kit/log v0.1.0/go.mod h1:zbhenjAZHb184qTLMA9ZjW7ThYL0H2mk7Q6pNt4vbaY=
github.com/go-logfmt/logfmt v0.5.0 h1:TrB8swr/68K7m9CcGut2g3UOihhbcbiMAYiuTXdEih4=
github.com/go-logfmt/logfmt v0.5.0/go.mod h1:wCYkCAKZfumFQihp8CzCvQ3paCTfi41vtzG1KdI/P7A=
github.com/go-stack/stack v1.8.0 h1:5SgMzNM5HxrEjV0ww2lTmX6E2Izsfxas4+YHWRs3Lsk=
github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/melR3HDY=

{
  "schemaVersion": 1,
  "goal": "verify github.com/go-kit/log/level.AllowInfo in pkg:golang/github.com/go-kit/log@v0.1.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/go-kit/log@v0.1.0"
  ],
  "symbols": [
    "github.com/go-kit/log/level.AllowInfo"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}

package main

import (
	"bytes"
	"errors"
	"fmt"
	"os"
	"strings"

	"github.com/go-kit/log"
	"github.com/go-kit/log/level"
)

func main() {
	if err := runTests(); err != nil {
		fmt.Fprintf(os.Stderr, "Contract test failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("All contract tests passed successfully.")
}

func runTests() error {
	// 1. AllowInfo allows error, warn, and info level log events to pass through to the underlying logger
	{
		var buf bytes.Buffer
		baseLogger := log.NewLogfmtLogger(&buf)
		filterLogger := level.NewFilter(baseLogger, level.AllowInfo())

		if err := level.Error(filterLogger).Log("msg", "critical error"); err != nil {
			return fmt.Errorf("level.Error log failed: %w", err)
		}
		if err := level.Warn(filterLogger).Log("msg", "warning event"); err != nil {
			return fmt.Errorf("level.Warn log failed: %w", err)
		}
		if err := level.Info(filterLogger).Log("msg", "informational event"); err != nil {
			return fmt.Errorf("level.Info log failed: %w", err)
		}

		lines := strings.Split(strings.TrimSpace(buf.String()), "\n")
		if len(lines) != 3 {
			return fmt.Errorf("expected 3 allowed lines, got %d", len(lines))
		}
		if lines[0] != `level=error msg="critical error"` {
			return fmt.Errorf("unexpected error line: %q", lines[0])
		}
		if lines[1] != `level=warn msg="warning event"` {
			return fmt.Errorf("unexpected warn line: %q", lines[1])
		}
		if lines[2] != `level=info msg="informational event"` {
			return fmt.Errorf("unexpected info line: %q", lines[2])
		}
	}

	// 2. AllowInfo squelches debug level log events by default without returning an error
	{
		var buf bytes.Buffer
		baseLogger := log.NewLogfmtLogger(&buf)
		filterLogger := level.NewFilter(baseLogger, level.AllowInfo())

		err := level.Debug(filterLogger).Log("msg", "debug detail", "code", 42)
		if err != nil {
			return fmt.Errorf("expected nil error on squelched debug log, got: %w", err)
		}
		if buf.Len() != 0 {
			return fmt.Errorf("expected empty buffer for squelched debug, got: %q", buf.String())
		}
	}

	// 3. AllowInfo passes non-leveled log events through unmodified by default
	{
		var buf bytes.Buffer
		baseLogger := log.NewLogfmtLogger(&buf)
		filterLogger := level.NewFilter(baseLogger, level.AllowInfo())

		if err := filterLogger.Log("msg", "unleveled event", "status", "ok"); err != nil {
			return fmt.Errorf("non-leveled log failed: %w", err)
		}
		out := strings.TrimSpace(buf.String())
		if out != `msg="unleveled event" status=ok` {
			return fmt.Errorf("unexpected unleveled output: %q", out)
		}
	}

	// 4. AllowInfo returns ErrNotAllowed when a disallowed debug log event is squelched
	{
		var buf bytes.Buffer
		baseLogger := log.NewLogfmtLogger(&buf)
		errDisallowed := errors.New("level not allowed")
		filterLogger := level.NewFilter(baseLogger, level.AllowInfo(), level.ErrNotAllowed(errDisallowed))

		err := level.Debug(filterLogger).Log("msg", "debug event")
		if !errors.Is(err, errDisallowed) {
			return fmt.Errorf("expected ErrNotAllowed error, got: %v", err)
		}
		if buf.Len() != 0 {
			return fmt.Errorf("expected empty buffer on disallowed log, got: %q", buf.String())
		}

		// Info event should still pass and return nil
		if err := level.Info(filterLogger).Log("msg", "allowed info"); err != nil {
			return fmt.Errorf("info log should succeed with ErrNotAllowed option, got: %w", err)
		}
		out := strings.TrimSpace(buf.String())
		if out != `level=info msg="allowed info"` {
			return fmt.Errorf("unexpected info output: %q", out)
		}
	}

	// 5. AllowInfo with SquelchNoLevel squelches log events that lack a level
	{
		var buf bytes.Buffer
		baseLogger := log.NewLogfmtLogger(&buf)
		errNoLevel := errors.New("no level provided")
		filterLogger := level.NewFilter(
			baseLogger,
			level.AllowInfo(),
			level.SquelchNoLevel(true),
			level.ErrNoLevel(errNoLevel),
		)

		err := filterLogger.Log("msg", "missing level")
		if !errors.Is(err, errNoLevel) {
			return fmt.Errorf("expected ErrNoLevel error, got: %v", err)
		}
		if buf.Len() != 0 {
			return fmt.Errorf("expected empty buffer on squelched unleveled log, got: %q", buf.String())
		}

		// Leveled info event should pass
		if err := level.Info(filterLogger).Log("msg", "has level"); err != nil {
			return fmt.Errorf("leveled info log should pass, got: %w", err)
		}
		out := strings.TrimSpace(buf.String())
		if out != `level=info msg="has level"` {
			return fmt.Errorf("unexpected output: %q", out)
		}
	}

	// 6. AllowInfo works with contextual loggers created via log.With and log.NewLogfmtLogger
	{
		var buf bytes.Buffer
		baseLogger := log.NewLogfmtLogger(&buf)
		filterLogger := level.NewFilter(baseLogger, level.AllowInfo())
		ctxLogger := log.With(filterLogger, "service", "verifier")

		if err := level.Info(ctxLogger).Log("event", "started"); err != nil {
			return fmt.Errorf("context info log failed: %w", err)
		}
		if err := level.Debug(ctxLogger).Log("event", "ignored"); err != nil {
			return fmt.Errorf("context debug log failed: %w", err)
		}

		out := strings.TrimSpace(buf.String())
		if out != `level=info service=verifier event=started` {
			return fmt.Errorf("unexpected context logger output: %q", out)
		}
	}

	return nil
}