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

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/panics.Recovered 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/panics.Recovered

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:fc656a634c55f37dc607ac2c362e495f04dce20aeda89d66073075aa944552f9","contract":["panics.Recovered captures panic value and call stack from a caught panic","panics.Recovered.AsError converts recovered panic into an unwrappable error","panics.Recovered.String returns formatted panic message with stacktrace","panics.Recovered is nil when no panic occurs"],"goal":"verify github.com/sourcegraph/conc/panics.Recovered 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/panics.Recovered"]},"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/panics.Recovered"],"verifierAdapter":"golang@1"}

module example.com/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 (
	"errors"
	"fmt"

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

func main() {
	var catcher panics.Catcher
	catcher.Try(func() {
		panic(errors.New("unexpected failure in task"))
	})

	recovered := catcher.Recovered()
	if recovered != nil {
		fmt.Printf("Caught panic: %v\n", recovered.Value)
		err := recovered.AsError()
		fmt.Printf("As error: %v\n", err)
	}
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/sourcegraph/conc/panics.Recovered 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/panics.Recovered"
  ]
}

package main

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

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

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

func runTests() error {
	// 1. panics.Recovered captures panic value and call stack from a caught panic
	var catcher panics.Catcher
	catcher.Try(func() {
		panic("test-panic-payload")
	})
	rec := catcher.Recovered()
	if rec == nil {
		return errors.New("expected non-nil Recovered, got nil")
	}
	if rec.Value != "test-panic-payload" {
		return fmt.Errorf("expected value 'test-panic-payload', got %v", rec.Value)
	}
	if len(rec.Stack) == 0 {
		return errors.New("expected non-empty stack in Recovered")
	}
	if len(rec.Callers) == 0 {
		return errors.New("expected non-empty Callers in Recovered")
	}

	// 2. panics.Recovered.AsError converts recovered panic into an unwrappable error
	sentinelErr := errors.New("sentinel error")
	recErr := panics.Try(func() {
		panic(sentinelErr)
	})
	if recErr == nil {
		return errors.New("expected non-nil Recovered from panics.Try")
	}
	err := recErr.AsError()
	if err == nil {
		return errors.New("expected non-nil error from recErr.AsError()")
	}
	if !errors.Is(err, sentinelErr) {
		return fmt.Errorf("expected error to unwrap to sentinelErr, got %v", err)
	}

	// 3. panics.Recovered.String returns formatted panic message with stacktrace
	str := rec.String()
	if !strings.Contains(str, "panic: test-panic-payload") {
		return fmt.Errorf("expected String() to contain 'panic: test-panic-payload', got %q", str)
	}
	if !strings.Contains(str, "stacktrace:") {
		return fmt.Errorf("expected String() to contain 'stacktrace:', got %q", str)
	}

	// 4. panics.Recovered is nil when no panic occurs
	noPanicRec := panics.Try(func() {
		// no-op
	})
	if noPanicRec != nil {
		return fmt.Errorf("expected nil Recovered when no panic occurs, got %v", noPanicRec)
	}

	return nil
}