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

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 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

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:df73d4f390d7f8da5e1711441f56d99a820596665855d47fa5eff8929cd2e134","contract":["diskv.New creates a Diskv store and Write stores key-value pairs to disk","diskv.Read retrieves stored data and reports error for non-existent keys","diskv.Has checks key existence and Erase deletes a key from disk","diskv.Keys streams stored keys over a channel","diskv.EraseAll removes all stored keys from the store"],"goal":"verify github.com/peterbourgon/diskv/v3 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"]},"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"],"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-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{}
	}

	d := diskv.New(diskv.Options{
		BasePath:     filepath.Join(tempDir, "data"),
		Transform:    flatTransform,
		CacheSizeMax: 1024 * 1024,
	})

	key := "greeting"
	val := []byte("hello diskv")

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

	if !d.Has(key) {
		fmt.Fprintf(os.Stderr, "expected key %q to exist\n", key)
		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("Read %q: %s\n", key, string(readVal))

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

{
  "schemaVersion": 1,
  "goal": "verify github.com/peterbourgon/diskv/v3 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"
  ]
}

package main

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

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

func main() {
	tempDir, err := os.MkdirTemp("", "diskv-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)

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

	// 1. diskv.New creates a Diskv store and Write stores key-value pairs to disk
	baseDir1 := filepath.Join(tempDir, "store1")
	d1 := diskv.New(diskv.Options{
		BasePath:     baseDir1,
		Transform:    flatTransform,
		CacheSizeMax: 1024 * 1024,
	})
	key1 := "alpha"
	val1 := []byte("alpha-payload")
	if err := d1.Write(key1, val1); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: write returned error: %v\n", err)
		os.Exit(1)
	}
	if _, err := os.Stat(filepath.Join(baseDir1, key1)); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 1 failed: expected file on disk: %v\n", err)
		os.Exit(1)
	}

	// 2. diskv.Read retrieves stored data and reports error for non-existent keys
	gotVal1, err := d1.Read(key1)
	if err != nil || !bytes.Equal(gotVal1, val1) {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: read returned %v, err %v\n", gotVal1, err)
		os.Exit(1)
	}
	if _, err := d1.Read("non-existent-key"); err == nil {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: read of missing key did not return error\n")
		os.Exit(1)
	}

	// 3. diskv.Has checks key existence and Erase deletes a key from disk
	if !d1.Has(key1) {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: Has returned false for existing key\n")
		os.Exit(1)
	}
	if d1.Has("missing-key") {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: Has returned true for missing key\n")
		os.Exit(1)
	}
	if err := d1.Erase(key1); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: erase returned error: %v\n", err)
		os.Exit(1)
	}
	if d1.Has(key1) {
		fmt.Fprintf(os.Stderr, "assertion 3 failed: Has returned true after erase\n")
		os.Exit(1)
	}

	// 4. diskv.Keys streams stored keys over a channel
	baseDir2 := filepath.Join(tempDir, "store2")
	d2 := diskv.New(diskv.Options{
		BasePath:     baseDir2,
		Transform:    flatTransform,
		CacheSizeMax: 1024 * 1024,
	})
	expectedKeys := map[string]bool{
		"item-1": true,
		"item-2": true,
		"item-3": true,
	}
	for k := range expectedKeys {
		if err := d2.Write(k, []byte("data-"+k)); err != nil {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: write %q error: %v\n", k, err)
			os.Exit(1)
		}
	}
	seenKeys := make(map[string]bool)
	for k := range d2.Keys(nil) {
		seenKeys[k] = true
	}
	if len(seenKeys) != len(expectedKeys) {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: expected %d keys, got %d\n", len(expectedKeys), len(seenKeys))
		os.Exit(1)
	}
	for k := range expectedKeys {
		if !seenKeys[k] {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: key %q missing from Keys stream\n", k)
			os.Exit(1)
		}
	}

	// 5. diskv.EraseAll removes all stored keys from the store
	if err := d2.EraseAll(); err != nil {
		fmt.Fprintf(os.Stderr, "assertion 5 failed: EraseAll error: %v\n", err)
		os.Exit(1)
	}
	for k := range expectedKeys {
		if d2.Has(k) {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: key %q still present after EraseAll\n", k)
			os.Exit(1)
		}
	}
	keyCountAfter := 0
	for range d2.Keys(nil) {
		keyCountAfter++
	}
	if keyCountAfter != 0 {
		fmt.Fprintf(os.Stderr, "assertion 5 failed: Keys channel yielded %d keys after EraseAll\n", keyCountAfter)
		os.Exit(1)
	}

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