golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4: modfile.Parse

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 pkg:golang/golang.org/x/mod@v0.6.0-dev.0.20220419223038-86c51ed26bb4
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/mod@v0.6.0-dev.0.20220419223038-86c51ed26bb4

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:sha256:1d7b3ce9e0421ddbc525a527a9f840d14112e1188cb8935ca451763e35339363","contract":["modfile.Parse parses a go.mod file into a File struct with module path and Go version","modfile.File.AddRequire adds a required dependency module path and version to the modfile","modfile.Format formats a modfile.File AST back into standard go.mod formatted bytes","modfile.File.DropRequire removes an existing requirement from the modfile AST","modfile.File.AddReplace adds a module replace directive to the modfile AST","modfile.Parse returns an error when parsing malformed go.mod content"],"goal":"verify pkg:golang/golang.org/x/mod@v0.6.0-dev.0.20220419223038-86c51ed26bb4","kind":"HOW","packages":["pkg:golang/golang.org/x/mod@v0.6.0-dev.0.20220419223038-86c51ed26bb4"],"schemaVersion":1,"symbols":["modfile.Parse"]},"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/golang.org/x/mod@v0.6.0-dev.0.20220419223038-86c51ed26bb4"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/mod@v0.6.0-dev.0.20220419223038-86c51ed26bb4","symbols":["modfile.Parse"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4

golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4 h1:6zppjxzCulZykYSLyVDYbneBfbaBIQPYMevg0bEwv2s=
golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=

package main

import (
	"fmt"
	"log"

	"golang.org/x/mod/modfile"
)

func main() {
	raw := []byte("module example.com/demo\n\ngo 1.18\n\nrequire github.com/stretchr/testify v1.8.0\n")

	f, err := modfile.Parse("go.mod", raw, nil)
	if err != nil {
		log.Fatalf("Parse error: %v", err)
	}

	fmt.Printf("Module path: %s\n", f.Module.Mod.Path)
	fmt.Printf("Go version: %s\n", f.Go.Version)

	if err := f.AddRequire("golang.org/x/sync", "v0.1.0"); err != nil {
		log.Fatalf("AddRequire error: %v", err)
	}

	formatted, err := f.Format()
	if err != nil {
		log.Fatalf("Format error: %v", err)
	}

	fmt.Printf("Formatted go.mod:\n%s\n", string(formatted))
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:golang/golang.org/x/mod@v0.6.0-dev.0.20220419223038-86c51ed26bb4",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/mod@v0.6.0-dev.0.20220419223038-86c51ed26bb4"
  ]
}

package main

import (
	"bytes"
	"fmt"
	"os"

	"golang.org/x/mod/modfile"
)

func main() {
	// 1. modfile.Parse parses a go.mod file into a File struct with module path and Go version
	{
		raw := []byte("module example.com/app\n\ngo 1.18\n\nrequire github.com/stretchr/testify v1.8.0\n")
		f, err := modfile.Parse("go.mod", raw, nil)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: modfile.Parse returned error: %v\n", err)
			os.Exit(1)
		}
		if f.Module == nil || f.Module.Mod.Path != "example.com/app" {
			fmt.Fprintf(os.Stderr, "FAIL: unexpected module path: %v\n", f.Module)
			os.Exit(1)
		}
		if f.Go == nil || f.Go.Version != "1.18" {
			fmt.Fprintf(os.Stderr, "FAIL: unexpected Go version: %v\n", f.Go)
			os.Exit(1)
		}
		if len(f.Require) != 1 || f.Require[0].Mod.Path != "github.com/stretchr/testify" || f.Require[0].Mod.Version != "v1.8.0" {
			fmt.Fprintf(os.Stderr, "FAIL: unexpected require statement: %v\n", f.Require)
			os.Exit(1)
		}
	}

	// 2. modfile.File.AddRequire adds a required dependency module path and version to the modfile
	{
		raw := []byte("module example.com/app\n\ngo 1.18\n")
		f, err := modfile.Parse("go.mod", raw, nil)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: modfile.Parse failed: %v\n", err)
			os.Exit(1)
		}
		err = f.AddRequire("golang.org/x/sync", "v0.1.0")
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: AddRequire failed: %v\n", err)
			os.Exit(1)
		}
		found := false
		for _, req := range f.Require {
			if req.Mod.Path == "golang.org/x/sync" && req.Mod.Version == "v0.1.0" {
				found = true
				break
			}
		}
		if !found {
			fmt.Fprintln(os.Stderr, "FAIL: AddRequire did not add the requirement")
			os.Exit(1)
		}
	}

	// 3. modfile.Format formats a modfile.File AST back into standard go.mod formatted bytes
	{
		raw := []byte("module example.com/app\n\ngo 1.18\n\nrequire golang.org/x/sync v0.10.0\n")
		f, err := modfile.Parse("go.mod", raw, nil)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: modfile.Parse failed: %v\n", err)
			os.Exit(1)
		}
		formatted, err := f.Format()
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: Format failed: %v\n", err)
			os.Exit(1)
		}
		if !bytes.Contains(formatted, []byte("module example.com/app")) ||
			!bytes.Contains(formatted, []byte("go 1.18")) ||
			!bytes.Contains(formatted, []byte("require golang.org/x/sync v0.10.0")) {
			fmt.Fprintf(os.Stderr, "FAIL: formatted content mismatch:\n%s\n", string(formatted))
			os.Exit(1)
		}
	}

	// 4. modfile.File.DropRequire removes an existing requirement from the modfile AST
	{
		raw := []byte("module example.com/app\n\ngo 1.18\n\nrequire (\n\tgolang.org/x/sync v0.10.0\n\tgolang.org/x/net v0.1.0\n)\n")
		f, err := modfile.Parse("go.mod", raw, nil)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: modfile.Parse failed: %v\n", err)
			os.Exit(1)
		}
		err = f.DropRequire("golang.org/x/net")
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: DropRequire failed: %v\n", err)
			os.Exit(1)
		}
		f.Cleanup()
		for _, req := range f.Require {
			if req.Mod.Path == "golang.org/x/net" {
				fmt.Fprintln(os.Stderr, "FAIL: DropRequire did not remove the requirement")
				os.Exit(1)
			}
		}
	}

	// 5. modfile.File.AddReplace adds a module replace directive to the modfile AST
	{
		raw := []byte("module example.com/app\n\ngo 1.18\n\nrequire golang.org/x/sync v0.10.0\n")
		f, err := modfile.Parse("go.mod", raw, nil)
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: modfile.Parse failed: %v\n", err)
			os.Exit(1)
		}
		err = f.AddReplace("golang.org/x/sync", "v0.10.0", "github.com/fork/sync", "v0.10.1")
		if err != nil {
			fmt.Fprintf(os.Stderr, "FAIL: AddReplace failed: %v\n", err)
			os.Exit(1)
		}
		found := false
		for _, rep := range f.Replace {
			if rep.Old.Path == "golang.org/x/sync" && rep.Old.Version == "v0.10.0" &&
				rep.New.Path == "github.com/fork/sync" && rep.New.Version == "v0.10.1" {
				found = true
				break
			}
		}
		if !found {
			fmt.Fprintln(os.Stderr, "FAIL: AddReplace did not add the replace directive")
			os.Exit(1)
		}
	}

	// 6. modfile.Parse returns an error when parsing malformed go.mod content
	{
		malformed := []byte("invalid syntax here {{{")
		_, err := modfile.Parse("go.mod", malformed, nil)
		if err == nil {
			fmt.Fprintln(os.Stderr, "FAIL: expected error on malformed go.mod, got nil")
			os.Exit(1)
		}
	}

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