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package gomplate
import (
"bytes"
"context"
"fmt"
"io"
"os"
"os/exec"
"os/signal"
"path/filepath"
"runtime"
"text/template"
"time"
"github.com/hairyhenderson/gomplate/v4/conv"
"github.com/hairyhenderson/gomplate/v4/internal/config"
)
// bindPlugins creates custom plugin functions for each plugin specified by
// the config, and adds them to the given funcMap. Uses the configuration's
// PluginTimeout as the default plugin Timeout. Errors if a function name is
// duplicated.
func bindPlugins(ctx context.Context, cfg *config.Config, funcMap template.FuncMap) error {
for k, v := range cfg.Plugins {
if _, ok := funcMap[k]; ok {
return fmt.Errorf("function %q is already bound, and can not be overridden", k)
}
// default the timeout to the one in the config
timeout := cfg.PluginTimeout
if v.Timeout != 0 {
timeout = v.Timeout
}
funcMap[k] = PluginFunc(ctx, v.Cmd, PluginOpts{
Timeout: timeout,
Pipe: v.Pipe,
Stderr: cfg.Stderr,
Args: v.Args,
})
}
return nil
}
// PluginOpts are options for controlling plugin function execution
type PluginOpts struct {
// Stderr can be set to redirect the plugin's stderr to a custom writer.
// Defaults to os.Stderr.
Stderr io.Writer
// Args are additional arguments to pass to the plugin. These precede any
// arguments passed to the plugin function at runtime.
Args []string
// Timeout is the maximum amount of time to wait for the plugin to complete.
// Defaults to 5 seconds.
Timeout time.Duration
// Pipe indicates whether the last argument should be piped to the plugin's
// stdin (true) or processed as a commandline argument (false)
Pipe bool
}
// PluginFunc creates a template function that runs an external process - either
// a shell script or commandline executable.
func PluginFunc(ctx context.Context, cmd string, opts PluginOpts) func(...interface{}) (interface{}, error) {
timeout := opts.Timeout
if timeout == 0 {
timeout = 5 * time.Second
}
stderr := opts.Stderr
if stderr == nil {
stderr = os.Stderr
}
plugin := &plugin{
ctx: ctx,
path: cmd,
args: opts.Args,
timeout: timeout,
pipe: opts.Pipe,
stderr: stderr,
}
return plugin.run
}
// plugin represents a custom function that binds to an external process to be executed
type plugin struct {
ctx context.Context
stderr io.Writer
path string
args []string
timeout time.Duration
pipe bool
}
// builds a command that's appropriate for running scripts
func (p *plugin) buildCommand(a []string) (name string, args []string) {
switch filepath.Ext(p.path) {
case ".ps1":
a = append([]string{"-File", p.path}, a...)
return findPowershell(), a
case ".cmd", ".bat":
a = append([]string{"/c", p.path}, a...)
return "cmd.exe", a
default:
return p.path, a
}
}
// finds the appropriate powershell command for the platform - prefers
// PowerShell Core (`pwsh`), but on Windows if it's not found falls back to
// Windows PowerShell (`powershell`).
func findPowershell() string {
if runtime.GOOS != "windows" {
return "pwsh"
}
_, err := exec.LookPath("pwsh")
if err != nil {
return "powershell"
}
return "pwsh"
}
func (p *plugin) run(args ...interface{}) (interface{}, error) {
a := conv.ToStrings(args...)
a = append(p.args, a...)
name, a := p.buildCommand(a)
ctx, cancel := context.WithTimeout(p.ctx, p.timeout)
defer cancel()
var stdin *bytes.Buffer
if p.pipe && len(a) > 0 {
stdin = bytes.NewBufferString(a[len(a)-1])
a = a[:len(a)-1]
}
c := exec.CommandContext(ctx, name, a...)
if stdin != nil {
c.Stdin = stdin
}
c.Stderr = p.stderr
outBuf := &bytes.Buffer{}
c.Stdout = outBuf
start := time.Now()
err := c.Start()
if err != nil {
return nil, fmt.Errorf("starting command: %w", err)
}
// make sure all signals are propagated
sigs := make(chan os.Signal, 1)
signal.Notify(sigs)
go func() {
select {
case sig := <-sigs:
// Pass signals to the sub-process
if c.Process != nil {
_ = c.Process.Signal(sig)
}
case <-ctx.Done():
}
}()
err = c.Wait()
elapsed := time.Since(start)
if ctx.Err() != nil {
err = fmt.Errorf("plugin timed out after %v: %w", elapsed, ctx.Err())
}
return outBuf.String(), err
}
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