github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8: NewWaitGroup

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/sourcegraph/conc.NewWaitGroup in pkg:golang/github.com/sourcegraph/conc@v0.3.1-0.20240121214520-5f936abd7ae8
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/sourcegraph/conc@v0.3.1-0.20240121214520-5f936abd7ae8
Demonstrate these symbols/APIs:
  - github.com/sourcegraph/conc.NewWaitGroup

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:f71e8fbf96d4e8bbcb709fcb0cc31c50598c1b7331698358dce618be19593508","contract":["conc.NewWaitGroup creates a WaitGroup that waits for all spawned goroutines to complete","conc.NewWaitGroup catches panics in spawned goroutines and propagates them on Wait","conc.NewWaitGroup catches panics and returns a Recovered object with WaitAndRecover","conc.NewWaitGroup returns nil from WaitAndRecover when all tasks complete without panicking","conc.NewWaitGroup supports running multiple concurrent tasks to completion"],"goal":"verify github.com/sourcegraph/conc.NewWaitGroup in pkg:golang/github.com/sourcegraph/conc@v0.3.1-0.20240121214520-5f936abd7ae8","kind":"HOW","packages":["pkg:golang/github.com/sourcegraph/conc@v0.3.1-0.20240121214520-5f936abd7ae8"],"schemaVersion":1,"symbols":["github.com/sourcegraph/conc.NewWaitGroup"]},"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/sourcegraph/conc@v0.3.1-0.20240121214520-5f936abd7ae8"],"schemaVersion":1,"subject":"pkg:golang/github.com/sourcegraph/conc@v0.3.1-0.20240121214520-5f936abd7ae8","symbols":["github.com/sourcegraph/conc.NewWaitGroup"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8

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/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8 h1:+jumHNA0Wrelhe64i8F6HNlS8pkoyMv5sreGx2Ry5Rw=
github.com/sourcegraph/conc v0.3.1-0.20240121214520-5f936abd7ae8/go.mod h1:3n1Cwaq1E1/1lhQhtRK2ts/ZwZEhjcQeJQ1RuC6Q/8U=
github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

package main

import (
	"fmt"
	"sync/atomic"

	"github.com/sourcegraph/conc"
)

func main() {
	wg := conc.NewWaitGroup()
	var processed atomic.Int64

	for i := 0; i < 5; i++ {
		taskID := i
		wg.Go(func() {
			processed.Add(1)
			fmt.Printf("Task %d completed\n", taskID)
		})
	}

	wg.Wait()
	fmt.Printf("All %d tasks finished successfully\n", processed.Load())
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/sourcegraph/conc.NewWaitGroup in pkg:golang/github.com/sourcegraph/conc@v0.3.1-0.20240121214520-5f936abd7ae8",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/sourcegraph/conc@v0.3.1-0.20240121214520-5f936abd7ae8"
  ],
  "symbols": [
    "github.com/sourcegraph/conc.NewWaitGroup"
  ]
}

package main

import (
	"fmt"
	"os"
	"sync/atomic"

	"github.com/sourcegraph/conc"
	"github.com/sourcegraph/conc/panics"
)

func main() {
	// Assertion 1: conc.NewWaitGroup creates a WaitGroup that waits for all spawned goroutines to complete
	{
		wg := conc.NewWaitGroup()
		var count atomic.Int64
		const totalTasks = 10

		for i := 0; i < totalTasks; i++ {
			wg.Go(func() {
				count.Add(1)
			})
		}

		wg.Wait()

		if got := count.Load(); got != totalTasks {
			fmt.Fprintf(os.Stderr, "assertion 1 failed: expected %d tasks to complete, got %d\n", totalTasks, got)
			os.Exit(1)
		}
	}

	// Assertion 2: conc.NewWaitGroup catches panics in spawned goroutines and propagates them on Wait
	{
		wg := conc.NewWaitGroup()
		expectedPanicMsg := "worker failed unexpectedly"

		wg.Go(func() {
			panic(expectedPanicMsg)
		})

		var caughtAny bool
		var caughtVal any
		func() {
			defer func() {
				if r := recover(); r != nil {
					caughtAny = true
					caughtVal = r
				}
			}()
			wg.Wait()
		}()

		if !caughtAny {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: expected panic from wg.Wait(), but none occurred\n")
			os.Exit(1)
		}

		rec, ok := caughtVal.(*panics.Recovered)
		if !ok || rec == nil {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: expected panic value of type *panics.Recovered, got %T\n", caughtVal)
			os.Exit(1)
		}
		if rec.Value != expectedPanicMsg {
			fmt.Fprintf(os.Stderr, "assertion 2 failed: expected recovered value %q, got %v\n", expectedPanicMsg, rec.Value)
			os.Exit(1)
		}
	}

	// Assertion 3: conc.NewWaitGroup catches panics and returns a Recovered object with WaitAndRecover
	{
		wg := conc.NewWaitGroup()
		expectedPanicVal := "isolated task failure"

		wg.Go(func() {
			panic(expectedPanicVal)
		})

		recovered := wg.WaitAndRecover()
		if recovered == nil {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: expected non-nil *panics.Recovered from WaitAndRecover\n")
			os.Exit(1)
		}
		if recovered.Value != expectedPanicVal {
			fmt.Fprintf(os.Stderr, "assertion 3 failed: expected panic value %q, got %v\n", expectedPanicVal, recovered.Value)
			os.Exit(1)
		}
	}

	// Assertion 4: conc.NewWaitGroup returns nil from WaitAndRecover when all tasks complete without panicking
	{
		wg := conc.NewWaitGroup()
		var completed atomic.Bool

		wg.Go(func() {
			completed.Store(true)
		})

		recovered := wg.WaitAndRecover()
		if recovered != nil {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: expected nil *panics.Recovered, got %+v\n", recovered)
			os.Exit(1)
		}
		if !completed.Load() {
			fmt.Fprintf(os.Stderr, "assertion 4 failed: expected task to have completed\n")
			os.Exit(1)
		}
	}

	// Assertion 5: conc.NewWaitGroup supports running multiple concurrent tasks to completion
	{
		wg := conc.NewWaitGroup()
		const taskCount = 20
		results := make([]int, taskCount)

		for i := 0; i < taskCount; i++ {
			idx := i
			wg.Go(func() {
				results[idx] = (idx + 1) * 2
			})
		}

		wg.Wait()

		for i := 0; i < taskCount; i++ {
			expected := (i + 1) * 2
			if results[i] != expected {
				fmt.Fprintf(os.Stderr, "assertion 5 failed: at index %d expected %d, got %d\n", i, expected, results[i])
				os.Exit(1)
			}
		}
	}

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