feat: cache dockerfile images through warmer (#2499)

* feat: cache dockerfile images through warmer

* Fix logical error in conditional statement

* Addressed review feedback

1. Updated help text for the --build-arg flag to indicate it should be used with the dockerfile flag.
2. Updated the documentation to include the optional --build-arg flag.
3. Added unit tests for `ParseDockerfile`, covering scenarios for missing Dockerfile, invalid Dockerfile, single stage Dockerfile, multi-stage Dockerfile and Args Dockerfile

---------

Co-authored-by: 连奔驰 <benchi.lian@thoughtworks.com>

pkg/cache/warm.go

@@ -18,13 +18,18 @@ package cache
 
 import (
 	"bytes"
+	"fmt"
 	"io"
 	"io/ioutil"
+	"net/http"
 	"os"
 	"path"
+	"regexp"
 
 	"github.com/GoogleContainerTools/kaniko/pkg/config"
+	"github.com/GoogleContainerTools/kaniko/pkg/dockerfile"
 	"github.com/GoogleContainerTools/kaniko/pkg/image/remote"
+	"github.com/GoogleContainerTools/kaniko/pkg/util"
 	"github.com/google/go-containerregistry/pkg/name"
 	v1 "github.com/google/go-containerregistry/pkg/v1"
 	"github.com/google/go-containerregistry/pkg/v1/tarball"
@@ -34,8 +39,21 @@ import (
 
 // WarmCache populates the cache
 func WarmCache(opts *config.WarmerOptions) error {
+	var dockerfileImages []string
 	cacheDir := opts.CacheDir
 	images := opts.Images
+
+	// if opts.image is empty,we need to parse dockerfilepath to get images list
+	if opts.DockerfilePath != "" {
+		var err error
+		if dockerfileImages, err = ParseDockerfile(opts); err != nil {
+			return errors.Wrap(err, "failed to parse Dockerfile")
+		}
+	}
+
+	// TODO: Implement deduplication logic later.
+	images = append(images, dockerfileImages...)
+
 	logrus.Debugf("%s\n", cacheDir)
 	logrus.Debugf("%s\n", images)
 
@@ -157,3 +175,41 @@ func (w *Warmer) Warm(image string, opts *config.WarmerOptions) (v1.Hash, error)
 
 	return digest, nil
 }
+
+func ParseDockerfile(opts *config.WarmerOptions) ([]string, error) {
+	var err error
+	var d []uint8
+	var baseNames []string
+	match, _ := regexp.MatchString("^https?://", opts.DockerfilePath)
+	if match {
+		response, e := http.Get(opts.DockerfilePath) //nolint:noctx
+		if e != nil {
+			return nil, e
+		}
+		d, err = ioutil.ReadAll(response.Body)
+	} else {
+		d, err = ioutil.ReadFile(opts.DockerfilePath)
+	}
+
+	if err != nil {
+		return nil, errors.Wrap(err, fmt.Sprintf("reading dockerfile at path %s", opts.DockerfilePath))
+	}
+
+	stages, _, err := dockerfile.Parse(d)
+	if err != nil {
+		return nil, errors.Wrap(err, "parsing dockerfile")
+	}
+
+	for i, s := range stages {
+		resolvedBaseName, err := util.ResolveEnvironmentReplacement(s.BaseName, opts.BuildArgs, false)
+		if err != nil {
+			return nil, errors.Wrap(err, fmt.Sprintf("resolving base name %s", s.BaseName))
+		}
+		if s.BaseName != resolvedBaseName {
+			stages[i].BaseName = resolvedBaseName
+		}
+		baseNames = append(baseNames, resolvedBaseName)
+	}
+	return baseNames, nil
+
+}