func packageDepToGoModCache()

in cmd/sync-tags/gomod.go [145:214]
52 lines of code
12 McCabe index (conditional complexity)

func packageDepToGoModCache(depPath, depPkg, commit, pseudoVersionOrTag string, commitTime time.Time) error {
	cacheDir := fmt.Sprintf("%s/pkg/mod/cache/download/%s/@v", os.Getenv("GOPATH"), depPkg)
	goModFile := fmt.Sprintf("%s/%s.mod", cacheDir, pseudoVersionOrTag)

	if _, err := os.Stat(goModFile); err == nil {
		fmt.Printf("%s for %s is already packaged up.\n", pseudoVersionOrTag, depPkg)
		return nil
	} else if err != nil && !os.IsNotExist(err) {
		return fmt.Errorf("could not check if %s exists: %v", goModFile, err)
	}

	fmt.Printf("Packaging up %s for %s into go mod cache.\n", pseudoVersionOrTag, depPkg)

	// create the cache if it doesn't exist
	if err := os.MkdirAll(filepath.Dir(goModFile), os.FileMode(0755)); err != nil {
		return fmt.Errorf("unable to create %s directory: %v", cacheDir, err)
	}

	// checkout the dep repo to the commit at the tag
	checkoutCommand := exec.Command("git", "checkout", commit)
	checkoutCommand.Dir = fmt.Sprintf("%s/src/%s", os.Getenv("GOPATH"), depPkg)
	checkoutCommand.Stdout = os.Stdout
	checkoutCommand.Stderr = os.Stderr
	if err := checkoutCommand.Run(); err != nil {
		return fmt.Errorf("failed to checkout %s at %s: %v", depPkg, commit, err)
	}

	// copy go.mod to the cache dir
	if err := copyFile(fmt.Sprintf("%s/go.mod", depPath), goModFile); err != nil {
		return fmt.Errorf("unable to copy %s file to %s to gomod cache for %s: %v", fmt.Sprintf("%s/go.mod", depPath), goModFile, depPkg, err)
	}

	// create info file in the cache dir
	moduleInfo := ModuleInfo{
		Version: pseudoVersionOrTag,
		Name:    commit,
		Short:   commit[:12],
		Time:    commitTime.UTC().Format("2006-01-02T15:04:05Z"),
	}

	moduleFile, err := json.Marshal(moduleInfo)
	if err != nil {
		return fmt.Errorf("error marshaling .info file for %s: %v", depPkg, err)
	}
	if err := ioutil.WriteFile(fmt.Sprintf("%s/%s.info", cacheDir, pseudoVersionOrTag), moduleFile, 0644); err != nil {
		return fmt.Errorf("failed to write %s file for %s: %v", fmt.Sprintf("%s/%s.info", cacheDir, pseudoVersionOrTag), depPkg, err)
	}

	// create the zip file in the cache dir. This zip file has the same hash
	// as of the zip file that would have been created by go mod download.
	zipCommand := exec.Command("/gomod-zip", "--package-name", depPkg, "--pseudo-version", pseudoVersionOrTag)
	zipCommand.Stdout = os.Stdout
	zipCommand.Stderr = os.Stderr
	if err := zipCommand.Run(); err != nil {
		return fmt.Errorf("failed to run gomod-zip for %s at %s: %v", depPkg, pseudoVersionOrTag, err)
	}

	// append the pseudoVersion to the list file in the cache dir
	listFile, err := os.OpenFile(fmt.Sprintf("%s/list", cacheDir), os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		return fmt.Errorf("unable to open list file in %s: %v", cacheDir, err)
	}
	defer listFile.Close()

	if _, err := listFile.WriteString(fmt.Sprintf("%s\n", pseudoVersionOrTag)); err != nil {
		return fmt.Errorf("unable to write to list file in %s: %v", cacheDir, err)
	}

	return nil
}