Merge pull request #8157 from dokku/7102-buildpacks-app-json

Add support for specifying buildpacks via app.json
2026-04-26 04:07:14 -04:00
parent f30da59b84 08596c9648
commit 0a6eb14dd1
12 changed files with 297 additions and 16 deletions
--- a/docs/appendices/file-formats/app-json.md
+++ b/docs/appendices/file-formats/app-json.md
@@ -5,6 +5,25 @@
 > [!IMPORTANT]
 > While the `app.json` format used by Dokku is based on the one [supported by Heroku](https://devcenter.heroku.com/articles/app-json-schema), not all Heroku functionality is supported by Dokku.

+## Buildpacks
+
+```json
+{
+  "buildpacks": [
+    {
+      "url": "heroku/python"
+    },
+    {
+      "url": "https://github.com/heroku/heroku-buildpack-nodejs.git"
+    }
+  ]
+}
+```
+
+(list, optional) A list of buildpacks to use when deploying the app. Each entry is an object with a `url` property. Buildpacks specified via the `buildpacks:add` or `buildpacks:set` commands take precedence over those specified in `app.json`. Buildpack URLs may use the shorthand format (e.g., `heroku/python`) which will be expanded to the full GitHub URL.
+
+- `url`: (string, required) The URL or shorthand reference of the buildpack.
+
 ## Cron

 ```json
--- a/docs/deployment/builders/buildpack-management.md
+++ b/docs/deployment/builders/buildpack-management.md
@@ -130,6 +130,24 @@ This will use the latest commit on the `master` branch of the specified buildpac
 dokku buildpacks:set node-js-app https://github.com/heroku/heroku-buildpack-nodejs#v87
 ```

+### Specifying buildpacks via app.json
+
+Buildpacks can also be specified in the `app.json` file at the root of your repository:
+
+```json
+{
+  "buildpacks": [
+    {
+      "url": "heroku/python"
+    }
+  ]
+}
+```
+
+Buildpacks configured via `buildpacks:add` or `buildpacks:set` commands take precedence over those specified in `app.json`. If no buildpacks are configured via commands and `app.json` contains a `buildpacks` entry, those buildpacks will be used.
+
+Shorthand buildpack references (e.g., `heroku/python`) are expanded to full GitHub URLs automatically.
+
 ### Displaying buildpack reports for an app

 You can get a report about the app's buildpacks status using the `buildpacks:report` command:
--- a/plugins/app-json/appjson.go
+++ b/plugins/app-json/appjson.go
@@ -26,6 +26,9 @@ var (

 // AppJSON is a struct that represents an app.json file as understood by Dokku
 type AppJSON struct {
+	// Buildpacks is a list of buildpacks to use for the app
+	Buildpacks []Buildpack `json:"buildpacks"`
+
 	// Cron is a list of cron tasks to execute
 	Cron []CronTask `json:"cron"`

@@ -51,6 +54,12 @@ type AppJSON struct {
 	} `json:"scripts"`
 }

+// Buildpack is a struct that represents a single buildpack
+type Buildpack struct {
+	// URL is the URL of the buildpack
+	URL string `json:"url"`
+}
+
 // CronTask is a struct that represents a single cron task from an app.json file
 type CronTask struct {
 	// Command is the command to execute
--- a/plugins/buildpacks/buildpacks_test.go
+++ b/plugins/buildpacks/buildpacks_test.go
@@ -0,0 +1,141 @@
+package buildpacks
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	. "github.com/onsi/gomega"
+)
+
+func setupTestEnvironment(t *testing.T) string {
+	t.Helper()
+	tmpDir, err := os.MkdirTemp("", "buildpacks-test")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	os.Setenv("DOKKU_LIB_ROOT", tmpDir)
+	os.Setenv("PLUGIN_PATH", "/var/lib/dokku/plugins")
+	os.Setenv("PLUGIN_ENABLED_PATH", "/var/lib/dokku/plugins/enabled")
+
+	return tmpDir
+}
+
+func teardownTestEnvironment(tmpDir string) {
+	os.RemoveAll(tmpDir)
+}
+
+func TestValidBuildpackURL(t *testing.T) {
+	RegisterTestingT(t)
+
+	url, err := validBuildpackURL("")
+	Expect(err).To(HaveOccurred())
+	Expect(err.Error()).To(ContainSubstring("Must specify a buildpack"))
+
+	url, err = validBuildpackURL("heroku/nodejs")
+	Expect(err).NotTo(HaveOccurred())
+	Expect(url).To(Equal("https://github.com/heroku/heroku-buildpack-nodejs.git"))
+
+	url, err = validBuildpackURL("heroku/python")
+	Expect(err).NotTo(HaveOccurred())
+	Expect(url).To(Equal("https://github.com/heroku/heroku-buildpack-python.git"))
+
+	url, err = validBuildpackURL("heroku-community/apt")
+	Expect(err).NotTo(HaveOccurred())
+	Expect(url).To(Equal("https://github.com/heroku/heroku-buildpack-apt.git"))
+
+	url, err = validBuildpackURL("https://github.com/heroku/heroku-buildpack-nodejs.git")
+	Expect(err).NotTo(HaveOccurred())
+	Expect(url).To(Equal("https://github.com/heroku/heroku-buildpack-nodejs.git"))
+
+	url, err = validBuildpackURL("https://github.com/heroku/heroku-buildpack-nodejs")
+	Expect(err).NotTo(HaveOccurred())
+	Expect(url).To(Equal("https://github.com/heroku/heroku-buildpack-nodejs"))
+
+	url, err = validBuildpackURL("git://github.com/heroku/heroku-buildpack-nodejs.git")
+	Expect(err).NotTo(HaveOccurred())
+	Expect(url).To(Equal("git://github.com/heroku/heroku-buildpack-nodejs.git"))
+
+	_, err = validBuildpackURL("nodejs")
+	Expect(err).To(HaveOccurred())
+	Expect(err.Error()).To(ContainSubstring("Invalid buildpack specified"))
+
+	_, err = validBuildpackURL("/nodejs")
+	Expect(err).To(HaveOccurred())
+	Expect(err.Error()).To(ContainSubstring("Invalid buildpack specified"))
+}
+
+func TestGetBuildpacksEmpty(t *testing.T) {
+	RegisterTestingT(t)
+	tmpDir := setupTestEnvironment(t)
+	defer teardownTestEnvironment(tmpDir)
+
+	buildpacks, err := getBuildpacks("test-app")
+	Expect(err).NotTo(HaveOccurred())
+	Expect(buildpacks).To(BeEmpty())
+}
+
+func TestGetBuildpacksFromProperties(t *testing.T) {
+	RegisterTestingT(t)
+	tmpDir := setupTestEnvironment(t)
+	defer teardownTestEnvironment(tmpDir)
+
+	propDir := filepath.Join(tmpDir, "config", "buildpacks", "test-app")
+	Expect(os.MkdirAll(propDir, 0755)).To(Succeed())
+	Expect(os.WriteFile(filepath.Join(propDir, "buildpacks"), []byte("https://github.com/heroku/heroku-buildpack-nodejs.git\nhttps://github.com/heroku/heroku-buildpack-python.git\n"), 0644)).To(Succeed())
+
+	buildpacks, err := getBuildpacks("test-app")
+	Expect(err).NotTo(HaveOccurred())
+	Expect(buildpacks).To(HaveLen(2))
+	Expect(buildpacks[0]).To(Equal("https://github.com/heroku/heroku-buildpack-nodejs.git"))
+	Expect(buildpacks[1]).To(Equal("https://github.com/heroku/heroku-buildpack-python.git"))
+}
+
+func TestGetBuildpacksFromAppJSON(t *testing.T) {
+	RegisterTestingT(t)
+	tmpDir := setupTestEnvironment(t)
+	defer teardownTestEnvironment(tmpDir)
+
+	appJSONDir := filepath.Join(tmpDir, "data", "app-json", "test-app")
+	Expect(os.MkdirAll(appJSONDir, 0755)).To(Succeed())
+	Expect(os.WriteFile(filepath.Join(appJSONDir, "app.json"), []byte(`{"buildpacks": [{"url": "https://github.com/heroku/heroku-buildpack-nodejs.git"}]}`), 0644)).To(Succeed())
+
+	buildpacks, err := getBuildpacks("test-app")
+	Expect(err).NotTo(HaveOccurred())
+	Expect(buildpacks).To(HaveLen(1))
+	Expect(buildpacks[0]).To(Equal("https://github.com/heroku/heroku-buildpack-nodejs.git"))
+}
+
+func TestGetBuildpacksPropertiesOverrideAppJSON(t *testing.T) {
+	RegisterTestingT(t)
+	tmpDir := setupTestEnvironment(t)
+	defer teardownTestEnvironment(tmpDir)
+
+	propDir := filepath.Join(tmpDir, "config", "buildpacks", "test-app")
+	Expect(os.MkdirAll(propDir, 0755)).To(Succeed())
+	Expect(os.WriteFile(filepath.Join(propDir, "buildpacks"), []byte("https://github.com/heroku/heroku-buildpack-ruby.git\n"), 0644)).To(Succeed())
+
+	appJSONDir := filepath.Join(tmpDir, "data", "app-json", "test-app")
+	Expect(os.MkdirAll(appJSONDir, 0755)).To(Succeed())
+	Expect(os.WriteFile(filepath.Join(appJSONDir, "app.json"), []byte(`{"buildpacks": [{"url": "https://github.com/heroku/heroku-buildpack-nodejs.git"}]}`), 0644)).To(Succeed())
+
+	buildpacks, err := getBuildpacks("test-app")
+	Expect(err).NotTo(HaveOccurred())
+	Expect(buildpacks).To(HaveLen(1))
+	Expect(buildpacks[0]).To(Equal("https://github.com/heroku/heroku-buildpack-ruby.git"))
+}
+
+func TestGetBuildpacksAppJSONEmptyArray(t *testing.T) {
+	RegisterTestingT(t)
+	tmpDir := setupTestEnvironment(t)
+	defer teardownTestEnvironment(tmpDir)
+
+	appJSONDir := filepath.Join(tmpDir, "data", "app-json", "test-app")
+	Expect(os.MkdirAll(appJSONDir, 0755)).To(Succeed())
+	Expect(os.WriteFile(filepath.Join(appJSONDir, "app.json"), []byte(`{"buildpacks": []}`), 0644)).To(Succeed())
+
+	buildpacks, err := getBuildpacks("test-app")
+	Expect(err).NotTo(HaveOccurred())
+	Expect(buildpacks).To(BeEmpty())
+}
--- a/plugins/buildpacks/functions.go
+++ b/plugins/buildpacks/functions.go
@@ -8,9 +8,50 @@ import (
 	"regexp"
 	"strings"

+	appjson "github.com/dokku/dokku/plugins/app-json"
 	"github.com/dokku/dokku/plugins/common"
 )

+// getBuildpacks returns the buildpacks for a given app
+// the order of application is:
+// 1. .buildpacks: if it exists, use it
+// 2. app.json: if it exists and has buildpacks, use them
+// 3. buildpack properties: if they exist, use them
+// 4. buildpack detection
+func getBuildpacks(appName string) ([]string, error) {
+	buildpacks, err := common.PropertyListGet("buildpacks", appName, "buildpacks")
+	if err != nil {
+		return buildpacks, err
+	}
+
+	if len(buildpacks) > 0 {
+		return buildpacks, nil
+	}
+
+	results, _ := common.CallPlugnTrigger(common.PlugnTriggerInput{
+		Trigger: "git-get-property",
+		Args:    []string{appName, "source-image"},
+	})
+	if results.StdoutContents() != "" {
+		return buildpacks, nil
+	}
+
+	appJSON, err := appjson.GetAppJSON(appName)
+	if err != nil {
+		return buildpacks, err
+	}
+
+	if len(appJSON.Buildpacks) == 0 {
+		return buildpacks, nil
+	}
+
+	for _, b := range appJSON.Buildpacks {
+		buildpacks = append(buildpacks, b.URL)
+	}
+
+	return buildpacks, nil
+}
+
 func rewriteBuildpacksFile(sourceWorkDir string) error {
 	buildpacksPath := filepath.Join(sourceWorkDir, ".buildpacks")
 	if !common.FileExists(buildpacksPath) {
@@ -27,6 +68,10 @@ func rewriteBuildpacksFile(sourceWorkDir string) error {
 			continue
 		}

+		if strings.HasPrefix(buildpack, "#") {
+			continue
+		}
+
 		buildpack, err = validBuildpackURL(buildpack)
 		if err != nil {
 			return fmt.Errorf("Unable to parse .buildpacks file, line %d: %s", i, err)
--- a/plugins/buildpacks/go.mod
+++ b/plugins/buildpacks/go.mod
@@ -3,6 +3,7 @@ module github.com/dokku/dokku/plugins/buildpacks
 go 1.25.5

 require (
+	github.com/dokku/dokku/plugins/app-json v0.0.0-00010101000000-000000000000
 	github.com/dokku/dokku/plugins/common v0.0.0-00010101000000-000000000000
 	github.com/spf13/pflag v1.0.10
 )
@@ -10,20 +11,30 @@ require (
 require (
 	github.com/alexellis/go-execute/v2 v2.2.1 // indirect
 	github.com/fatih/color v1.19.0 // indirect
+	github.com/google/go-cmp v0.7.0 // indirect
 	github.com/hashicorp/errwrap v1.0.0 // indirect
 	github.com/hashicorp/go-multierror v1.1.1 // indirect
+	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 // indirect
 	github.com/kr/fs v0.1.0 // indirect
 	github.com/mattn/go-colorable v0.1.14 // indirect
 	github.com/mattn/go-isatty v0.0.20 // indirect
 	github.com/melbahja/goph v1.5.0 // indirect
+	github.com/onsi/gomega v1.39.1 // indirect
 	github.com/otiai10/copy v1.14.1 // indirect
 	github.com/otiai10/mint v1.6.3 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pkg/sftp v1.13.10 // indirect
 	github.com/ryanuber/columnize v2.1.2+incompatible // indirect
+	github.com/tailscale/hujson v0.0.0-20250605163823-992244df8c5a // indirect
+	go.yaml.in/yaml/v3 v3.0.4 // indirect
 	golang.org/x/crypto v0.50.0 // indirect
+	golang.org/x/net v0.52.0 // indirect
 	golang.org/x/sync v0.20.0 // indirect
 	golang.org/x/sys v0.43.0 // indirect
+	golang.org/x/text v0.36.0 // indirect
+	k8s.io/utils v0.0.0-20240102154912-e7106e64919e // indirect
 )

+replace github.com/dokku/dokku/plugins/app-json => ../app-json
+
 replace github.com/dokku/dokku/plugins/common => ../common
--- a/plugins/buildpacks/go.sum
+++ b/plugins/buildpacks/go.sum
@@ -10,6 +10,8 @@ github.com/hashicorp/errwrap v1.0.0 h1:hLrqtEDnRye3+sgx6z4qVLNuviH3MR5aQ0ykNJa/U
 github.com/hashicorp/errwrap v1.0.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
 github.com/hashicorp/go-multierror v1.1.1 h1:H5DkEtf6CXdFp0N0Em5UCwQpXMWke8IA0+lD48awMYo=
 github.com/hashicorp/go-multierror v1.1.1/go.mod h1:iw975J/qwKPdAO1clOe2L8331t/9/fmwbPZ6JB6eMoM=
+github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 h1:Z9n2FFNUXsshfwJMBgNA0RU6/i7WVaAegv3PtuIHPMs=
+github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51/go.mod h1:CzGEWj7cYgsdH8dAjBGEr58BoE7ScuLd+fwFZ44+/x8=
 github.com/kr/fs v0.1.0 h1:Jskdu9ieNAYnjxsi0LbQp1ulIKZV1LAFgK1tWhpZgl8=
 github.com/kr/fs v0.1.0/go.mod h1:FFnZGqtBN9Gxj7eW1uZ42v5BccTP0vu6NEaFoC2HwRg=
 github.com/mattn/go-colorable v0.1.14 h1:9A9LHSqF/7dyVVX6g0U9cwm9pG3kP9gSzcuIPHPsaIE=
@@ -36,6 +38,8 @@ github.com/spf13/pflag v1.0.10 h1:4EBh2KAYBwaONj6b2Ye1GiHfwjqyROoF4RwYO+vPwFk=
 github.com/spf13/pflag v1.0.10/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/stretchr/testify v1.10.0 h1:Xv5erBjTwe/5IxqUQTdXv5kgmIvbHo3QQyRwhJsOfJA=
 github.com/stretchr/testify v1.10.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+github.com/tailscale/hujson v0.0.0-20250605163823-992244df8c5a h1:a6TNDN9CgG+cYjaeN8l2mc4kSz2iMiCDQxPEyltUV/I=
+github.com/tailscale/hujson v0.0.0-20250605163823-992244df8c5a/go.mod h1:EbW0wDK/qEUYI0A5bqq0C2kF8JTQwWONmGDBbzsxxHo=
 go.yaml.in/yaml/v3 v3.0.4 h1:tfq32ie2Jv2UxXFdLJdh3jXuOzWiL1fo0bu/FbuKpbc=
 go.yaml.in/yaml/v3 v3.0.4/go.mod h1:DhzuOOF2ATzADvBadXxruRBLzYTpT36CKvDb3+aBEFg=
 golang.org/x/crypto v0.50.0 h1:zO47/JPrL6vsNkINmLoo/PH1gcxpls50DNogFvB5ZGI=
@@ -51,5 +55,8 @@ golang.org/x/term v0.42.0 h1:UiKe+zDFmJobeJ5ggPwOshJIVt6/Ft0rcfrXZDLWAWY=
 golang.org/x/term v0.42.0/go.mod h1:Dq/D+snpsbazcBG5+F9Q1n2rXV8Ma+71xEjTRufARgY=
 golang.org/x/text v0.36.0 h1:JfKh3XmcRPqZPKevfXVpI1wXPTqbkE5f7JA92a55Yxg=
 golang.org/x/text v0.36.0/go.mod h1:NIdBknypM8iqVmPiuco0Dh6P5Jcdk8lJL0CUebqK164=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+k8s.io/utils v0.0.0-20240102154912-e7106e64919e h1:eQ/4ljkx21sObifjzXwlPKpdGLrCfRziVtos3ofG/sQ=
+k8s.io/utils v0.0.0-20240102154912-e7106e64919e/go.mod h1:OLgZIPagt7ERELqWJFomSt595RzquPNLL48iOWgYOg0=
--- a/plugins/buildpacks/triggers.go
+++ b/plugins/buildpacks/triggers.go
@@ -74,7 +74,7 @@ func TriggerPostDelete(appName string) error {

 // TriggerPostExtract writes a .buildpacks file into the app
 func TriggerPostExtract(appName string, sourceWorkDir string) error {
-	buildpacks, err := common.PropertyListGet("buildpacks", appName, "buildpacks")
+	buildpacks, err := getBuildpacks(appName)
 	if err != nil {
 		return nil
 	}
@@ -91,13 +91,20 @@ func TriggerPostExtract(appName string, sourceWorkDir string) error {

 	w := bufio.NewWriter(file)
 	for _, buildpack := range buildpacks {
+		buildpack, err = validBuildpackURL(buildpack)
+		if err != nil {
+			return err
+		}
+
 		fmt.Fprintln(w, buildpack)
 	}

 	if err = w.Flush(); err != nil {
 		return fmt.Errorf("Error writing .buildpacks file: %s", err.Error())
 	}
-	file.Chmod(0600)
+	if err = file.Chmod(0600); err != nil {
+		return fmt.Errorf("Error setting .buildpacks file permissions: %s", err.Error())
+	}

 	return nil
 }
--- a/plugins/scheduler-k3s/go.mod
+++ b/plugins/scheduler-k3s/go.mod
@@ -5,14 +5,14 @@ go 1.25.5
 require (
 	github.com/Masterminds/semver/v3 v3.4.0
 	github.com/cert-manager/cert-manager v1.20.2
-	github.com/dokku/dokku/plugins/app-json v0.0.0-20250618161309-8d0c35f1333c
-	github.com/dokku/dokku/plugins/common v0.0.0-20250618161309-8d0c35f1333c
-	github.com/dokku/dokku/plugins/config v0.0.0-20250618161309-8d0c35f1333c
-	github.com/dokku/dokku/plugins/cron v0.0.0-20250618161309-8d0c35f1333c
-	github.com/dokku/dokku/plugins/docker-options v0.0.0-20250618161309-8d0c35f1333c
-	github.com/dokku/dokku/plugins/logs v0.0.0-20250618161309-8d0c35f1333c
-	github.com/dokku/dokku/plugins/nginx-vhosts v0.0.0-20250618161309-8d0c35f1333c
-	github.com/dokku/dokku/plugins/registry v0.0.0-20250618161309-8d0c35f1333c
+	github.com/dokku/dokku/plugins/app-json v0.0.0-00010101000000-000000000000
+	github.com/dokku/dokku/plugins/common v0.0.0-00010101000000-000000000000
+	github.com/dokku/dokku/plugins/config v0.0.0-00010101000000-000000000000
+	github.com/dokku/dokku/plugins/cron v0.0.0-00010101000000-000000000000
+	github.com/dokku/dokku/plugins/docker-options v0.0.0-00010101000000-000000000000
+	github.com/dokku/dokku/plugins/logs v0.0.0-00010101000000-000000000000
+	github.com/dokku/dokku/plugins/nginx-vhosts v0.0.0-00010101000000-000000000000
+	github.com/dokku/dokku/plugins/registry v0.0.0-00010101000000-000000000000
 	github.com/fatih/color v1.19.0
 	github.com/fluxcd/pkg/kustomize v1.31.0
 	github.com/go-openapi/jsonpointer v0.23.1
--- a/tests.mk
+++ b/tests.mk
@@ -149,6 +149,7 @@ ci-go-coverage:
 	@$(MAKE) ci-go-coverage-plugin PLUGIN_NAME=common
 	@$(MAKE) ci-go-coverage-plugin PLUGIN_NAME=config
 	@$(MAKE) ci-go-coverage-plugin PLUGIN_NAME=network
+	@$(MAKE) ci-go-coverage-plugin PLUGIN_NAME=buildpacks

 ci-go-coverage-plugin:
 	mkdir -p test-results/coverage
@@ -177,9 +178,10 @@ go-tests:
 	@$(MAKE) go-test-plugin PLUGIN_NAME=common
 	@$(MAKE) go-test-plugin PLUGIN_NAME=config
 	@$(MAKE) go-test-plugin PLUGIN_NAME=network
+	@$(MAKE) go-test-plugin PLUGIN_NAME=buildpacks

 go-test-plugin:
-	cd plugins/$(PLUGIN_NAME) && go get github.com/onsi/gomega && DOKKU_ROOT=/home/dokku go test -v -p 1 -race -mod=readonly || exit $$?
+	cd plugins/$(PLUGIN_NAME) && go get github.com/onsi/gomega && DOKKU_ROOT=/home/dokku DOKKU_LIB_ROOT=/var/lib/dokku go test -v -p 1 -race -mod=readonly || exit $$?

 go-test-plugin-in-docker:
 	@echo running go unit tests...
--- a/tests/apps/dockerfile/app.json
+++ b/tests/apps/dockerfile/app.json
@@ -3,11 +3,6 @@
    "dokku-postgres",
    "dokku-redis"
  ],
-  "buildpacks": [
-    {
-      "url": "https://github.com/heroku/heroku-buildpack-nodejs"
-    }
-  ],
  "description": "Used in dokku's test suite",
  "env": {
    "SECRET_TOKEN": {
--- a/tests/unit/buildpacks.bats
+++ b/tests/unit/buildpacks.bats
@@ -336,6 +336,33 @@ teardown() {
  assert_output_contains "heroku-buildpack-python"
 }

+@test "(buildpacks) deploy with buildpacks from app.json" {
+  run deploy_app python dokku@$DOKKU_DOMAIN:$TEST_APP template_buildpacks_appjson
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output_contains "heroku-buildpack-python"
+}
+
+template_buildpacks_appjson() {
+  local APP="$1"
+  local APP_REPO_DIR="$2"
+  [[ -z "$APP" ]] && local APP="$TEST_APP"
+  echo "injecting app.json with buildpacks -> $APP_REPO_DIR/app.json"
+  cat <<EOF >"$APP_REPO_DIR/app.json"
+{
+  "buildpacks": [
+    {
+      "url": "heroku/python"
+    }
+  ]
+}
+EOF
+
+  echo "injecting requirements.txt -> $APP_REPO_DIR/requirements.txt"
+  touch "$APP_REPO_DIR/requirements.txt"
+}
+
 template_buildpacks_cleanup() {
  local APP="$1"
  local APP_REPO_DIR="$2"