terraform/config/module/get.go

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package module
import (
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"bytes"
"fmt"
"net/url"
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"os/exec"
"regexp"
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"syscall"
)
// Getter defines the interface that schemes must implement to download
// and update modules.
type Getter interface {
// Get downloads the given URL into the given directory. This always
// assumes that we're updating and gets the latest version that it can.
//
// The directory may already exist (if we're updating). If it is in a
// format that isn't understood, an error should be returned. Get shouldn't
// simply nuke the directory.
Get(string, *url.URL) error
}
// Getters is the mapping of scheme to the Getter implementation that will
// be used to get a dependency.
var Getters map[string]Getter
// forcedRegexp is the regular expression that finds forced getters. This
// syntax is schema::url, example: git::https://foo.com
var forcedRegexp = regexp.MustCompile(`^([A-Za-z]+)::(.+)$`)
func init() {
Getters = map[string]Getter{
"file": new(FileGetter),
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"git": new(GitGetter),
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"hg": new(HgGetter),
}
}
// Get downloads the module specified by src into the folder specified by
// dst. If dst already exists, Get will attempt to update it.
//
// src is a URL, whereas dst is always just a file path to a folder. This
// folder doesn't need to exist. It will be created if it doesn't exist.
func Get(dst, src string) error {
var force string
force, src = getForcedGetter(src)
u, err := url.Parse(src)
if err != nil {
return err
}
if force == "" {
force = u.Scheme
}
g, ok := Getters[force]
if !ok {
return fmt.Errorf(
"module download not supported for scheme '%s'", force)
}
err = g.Get(dst, u)
if err != nil {
err = fmt.Errorf("error downloading module '%s': %s", src, err)
}
return err
}
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// getRunCommand is a helper that will run a command and capture the output
// in the case an error happens.
func getRunCommand(cmd *exec.Cmd) error {
var buf bytes.Buffer
cmd.Stdout = &buf
cmd.Stderr = &buf
err := cmd.Run()
if err == nil {
return nil
}
if exiterr, ok := err.(*exec.ExitError); ok {
// The program has exited with an exit code != 0
if status, ok := exiterr.Sys().(syscall.WaitStatus); ok {
return fmt.Errorf(
"%s exited with %d: %s",
cmd.Path,
status.ExitStatus(),
buf.String())
}
}
return fmt.Errorf("error running %s: %s", cmd.Path, buf.String())
}
// getForcedGetter takes a source and returns the tuple of the forced
// getter and the raw URL (without the force syntax).
func getForcedGetter(src string) (string, string) {
var forced string
if ms := forcedRegexp.FindStringSubmatch(src); ms != nil {
forced = ms[1]
src = ms[2]
}
return forced, src
}