github.com/peterbourgon/diskv/v3 v3.0.1: Options

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/peterbourgon/diskv/v3.Options in pkg:golang/github.com/peterbourgon/diskv/v3@v3.0.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/peterbourgon/diskv/v3@v3.0.1
Demonstrate these symbols/APIs:
  - github.com/peterbourgon/diskv/v3.Options

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:d71a5f92457d68edfbcc7c493f6a53146d5f19af23c5c6bf37dd5a41afb5ee1b","contract":["diskv.Options BasePath specifies the root filesystem directory for stored keys","diskv.Options Transform defines custom directory nesting for persisted files","diskv.Options FilePerm and PathPerm configure file and directory permissions","diskv.Options CacheSizeMax caches read values in memory up to the configured limit","diskv.Options TempDir stages writes to temporary files before atomic placement"],"goal":"verify github.com/peterbourgon/diskv/v3.Options in pkg:golang/github.com/peterbourgon/diskv/v3@v3.0.1","kind":"HOW","packages":["pkg:golang/github.com/peterbourgon/diskv/v3@v3.0.1"],"schemaVersion":1,"symbols":["github.com/peterbourgon/diskv/v3.Options"]},"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/peterbourgon/diskv/v3@v3.0.1"],"schemaVersion":1,"subject":"pkg:golang/github.com/peterbourgon/diskv/v3@v3.0.1","symbols":["github.com/peterbourgon/diskv/v3.Options"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/peterbourgon/diskv/v3 v3.0.1

require github.com/google/btree v1.0.0 // indirect

github.com/google/btree v1.0.0 h1:0udJVsspx3VBr5FwtLhQQtuAsVc79tTq0ocGIPAU6qo=
github.com/google/btree v1.0.0/go.mod h1:lNA+9X1NB3Zf8V7Ke586lFgjr2dZNuvo3lPJSGZ5JPQ=
github.com/peterbourgon/diskv/v3 v3.0.1 h1:x06SQA46+PKIUftmEujdwSEpIx8kR+M9eLYsUxeYveU=
github.com/peterbourgon/diskv/v3 v3.0.1/go.mod h1:kJ5Ny7vLdARGU3WUuy6uzO6T0nb/2gWcT1JiBvRmb5o=

package main

import (
	"fmt"
	"os"
	"path/filepath"

	"github.com/peterbourgon/diskv/v3"
)

func main() {
	tempDir, err := os.MkdirTemp("", "diskv-options-demo-*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to create temp dir: %v\n", err)
		os.Exit(1)
	}
	defer os.RemoveAll(tempDir)

	flatTransform := func(s string) []string {
		return []string{}
	}

	opts := diskv.Options{
		BasePath:     filepath.Join(tempDir, "store"),
		Transform:    flatTransform,
		CacheSizeMax: 1024 * 1024,
		PathPerm:     0755,
		FilePerm:     0644,
		TempDir:      filepath.Join(tempDir, "staging"),
	}

	d := diskv.New(opts)

	key := "config-key"
	val := []byte("options-configured-data")

	if err := d.Write(key, val); err != nil {
		fmt.Fprintf(os.Stderr, "failed to write: %v\n", err)
		os.Exit(1)
	}

	readVal, err := d.Read(key)
	if err != nil {
		fmt.Fprintf(os.Stderr, "failed to read: %v\n", err)
		os.Exit(1)
	}

	fmt.Printf("Successfully stored and retrieved %q: %s\n", key, string(readVal))
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/peterbourgon/diskv/v3.Options in pkg:golang/github.com/peterbourgon/diskv/v3@v3.0.1",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/peterbourgon/diskv/v3@v3.0.1"
  ],
  "symbols": [
    "github.com/peterbourgon/diskv/v3.Options"
  ]
}

package main

import (
	"bytes"
	"fmt"
	"os"
	"path/filepath"

	"github.com/peterbourgon/diskv/v3"
)

func main() {
	tempDir, err := os.MkdirTemp("", "diskv-options-contract-*")
	if err != nil {
		fmt.Fprintf(os.Stderr, "setup failed: unable to create temp dir: %v\n", err)
		os.Exit(1)
	}
	defer os.RemoveAll(tempDir)

	// 1. diskv.Options BasePath specifies the root filesystem directory for stored keys
	baseDir := filepath.Join(tempDir, "base_test")
	d1 := diskv.New(diskv.Options{
		BasePath: baseDir,
	})
	if err := d1.Write("root-key", []byte("root-data")); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: write returned error: %v\n", err)
		os.Exit(1)
	}
	diskPath := filepath.Join(baseDir, "root-key")
	if _, err := os.Stat(diskPath); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: file not found at expected BasePath: %v\n", err)
		os.Exit(1)
	}
	val1, err := d1.Read("root-key")
	if err != nil || !bytes.Equal(val1, []byte("root-data")) {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: read returned unexpected value or error: %v\n", err)
		os.Exit(1)
	}

	// 2. diskv.Options Transform defines custom directory nesting for persisted files
	transformDir := filepath.Join(tempDir, "transform_test")
	customTransform := func(s string) []string {
		if len(s) >= 4 {
			return []string{s[0:2], s[2:4]}
		}
		return []string{}
	}
	d2 := diskv.New(diskv.Options{
		BasePath:  transformDir,
		Transform: customTransform,
	})
	if err := d2.Write("abcd12", []byte("nested-data")); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: write returned error: %v\n", err)
		os.Exit(1)
	}
	nestedPath := filepath.Join(transformDir, "ab", "cd", "abcd12")
	if _, err := os.Stat(nestedPath); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: nested file not found at %q: %v\n", nestedPath, err)
		os.Exit(1)
	}
	val2, err := d2.Read("abcd12")
	if err != nil || !bytes.Equal(val2, []byte("nested-data")) {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: read returned unexpected value or error: %v\n", err)
		os.Exit(1)
	}

	// 3. diskv.Options FilePerm and PathPerm configure file and directory permissions
	permDir := filepath.Join(tempDir, "perm_test")
	stagingDir := filepath.Join(tempDir, "perm_staging")
	d3 := diskv.New(diskv.Options{
		BasePath: permDir,
		TempDir:  stagingDir,
		PathPerm: 0750,
		FilePerm: 0640,
	})
	if err := d3.Write("perm-key", []byte("perm-data")); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: write returned error: %v\n", err)
		os.Exit(1)
	}
	permFile := filepath.Join(permDir, "perm-key")
	fi, err := os.Stat(permFile)
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: unable to stat perm file: %v\n", err)
		os.Exit(1)
	}
	if fi.Mode().Perm() != 0640 {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: expected file permissions 0640, got %04o\n", fi.Mode().Perm())
		os.Exit(1)
	}

	// 4. diskv.Options CacheSizeMax caches read values in memory up to the configured limit
	cacheDir := filepath.Join(tempDir, "cache_test")
	d4 := diskv.New(diskv.Options{
		BasePath:     cacheDir,
		CacheSizeMax: 1024 * 1024,
	})
	if err := d4.Write("cache-key", []byte("memory-cached-value")); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: write returned error: %v\n", err)
		os.Exit(1)
	}
	primed, err := d4.Read("cache-key")
	if err != nil || !bytes.Equal(primed, []byte("memory-cached-value")) {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: prime read failed: %v\n", err)
		os.Exit(1)
	}
	diskFile := filepath.Join(cacheDir, "cache-key")
	if err := os.Remove(diskFile); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: unable to remove disk file: %v\n", err)
		os.Exit(1)
	}
	cachedVal, err := d4.Read("cache-key")
	if err != nil {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: cached read failed after disk removal: %v\n", err)
		os.Exit(1)
	}
	if !bytes.Equal(cachedVal, []byte("memory-cached-value")) {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: unexpected cached value: %q\n", string(cachedVal))
		os.Exit(1)
	}

	// 5. diskv.Options TempDir stages writes to temporary files before atomic placement
	tempBaseDir := filepath.Join(tempDir, "temp_base")
	tempStagingDir := filepath.Join(tempDir, "temp_staging")
	d5 := diskv.New(diskv.Options{
		BasePath: tempBaseDir,
		TempDir:  tempStagingDir,
	})
	if err := d5.Write("atomic-key", []byte("atomic-data")); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 5 failed: write returned error: %v\n", err)
		os.Exit(1)
	}
	if info, err := os.Stat(tempStagingDir); err != nil || !info.IsDir() {
		fmt.Fprintf(os.Stderr, "assertion 5 failed: TempDir was not initialized as a directory: %v\n", err)
		os.Exit(1)
	}
	val5, err := d5.Read("atomic-key")
	if err != nil || !bytes.Equal(val5, []byte("atomic-data")) {
		fmt.Fprintf(os.Stderr, "assertion 5 failed: read returned unexpected value or error: %v\n", err)
		os.Exit(1)
	}

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