fix: respect the build-dir in app-json extraction

Because the app-json extraction happens before the build-dir is set, it doesn't end up respecting the value, and thus the user might get the wrong app.json file.

This takes advantage of path.Join()'s default of ignoring empty paths.

docs/development/plugin-triggers.md

@@ -221,6 +221,22 @@ set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
 # TODO
 ```
 
+### `builder-get-property`
+
+- Description: Return the value for an app's builder property
+- Invoked by:
+- Arguments: `$APP $KEY`
+- Example:
+
+```shell
+#!/usr/bin/env bash
+
+set -eo pipefail; [[ $DOKKU_TRACE ]] && set -x
+APP="$1"; PROPERTY="$2"
+
+# TODO
+```
+
 ### `builder-image-is-cnb`
 
 - Description: Checks if an image is cnb-based

plugins/app-json/triggers.go

@@ -83,9 +83,12 @@ func TriggerCorePostExtract(appName string, sourceWorkDir string) error {
 	b, _ := common.PlugnTriggerOutput("git-get-property", []string{appName, "source-image"}...)
 	appSourceImage := strings.TrimSpace(string(b[:]))
 
+	b, _ = common.PlugnTriggerOutput("builder-get-property", []string{appName, "build-dir"}...)
+	buildDir := strings.TrimSpace(string(b[:]))
+
 	repoDefaultAppJSONPath := path.Join(sourceWorkDir, "app.json")
 	if appSourceImage == "" {
-		repoAppJSONPath := path.Join(sourceWorkDir, appJSONPath)
+		repoAppJSONPath := path.Join(sourceWorkDir, buildDir, appJSONPath)
 		if !common.FileExists(repoAppJSONPath) {
 			if appJSONPath != "app.json" && common.FileExists(repoDefaultAppJSONPath) {
 				if err := os.Remove(repoDefaultAppJSONPath); err != nil {
@@ -105,7 +108,7 @@ func TriggerCorePostExtract(appName string, sourceWorkDir string) error {
 			}
 		}
 	} else {
-		if err := common.CopyFromImage(appName, appSourceImage, appJSONPath, processSpecificAppJSON); err != nil {
+		if err := common.CopyFromImage(appName, appSourceImage, path.Join(buildDir, appJSONPath), processSpecificAppJSON); err != nil {
 			return common.TouchFile(fmt.Sprintf("%s.missing", processSpecificAppJSON))
 		}
 	}

plugins/builder/Makefile

@@ -1,5 +1,5 @@
 SUBCOMMANDS = subcommands/report subcommands/set
-TRIGGERS = triggers/builder-detect triggers/builder-image-is-cnb triggers/builder-image-is-herokuish triggers/core-post-extract triggers/install triggers/post-app-clone-setup triggers/post-app-rename-setup triggers/post-delete triggers/report
+TRIGGERS = triggers/builder-detect triggers/builder-get-property triggers/builder-image-is-cnb triggers/builder-image-is-herokuish triggers/core-post-extract triggers/install triggers/post-app-clone-setup triggers/post-app-rename-setup triggers/post-delete triggers/report
 BUILD = commands subcommands triggers
 PLUGIN_NAME = builder
 

plugins/builder/src/triggers/triggers.go

@@ -21,6 +21,10 @@ func main() {
 	case "builder-detect":
 		appName := flag.Arg(0)
 		err = builder.TriggerBuilderDetect(appName)
+	case "builder-get-property":
+		appName := flag.Arg(0)
+		property := flag.Arg(1)
+		err = builder.TriggerBuilderGetProperty(appName, property)
 	case "builder-image-is-cnb":
 		appName := flag.Arg(0)
 		image := flag.Arg(1)

plugins/builder/triggers.go

@@ -1,6 +1,7 @@
 package builder
 
 import (
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"os"
@@ -26,6 +27,16 @@ func TriggerBuilderDetect(appName string) error {
 	return nil
 }
 
+// TriggerBuilderGetProperty writes the builder key to stdout for a given app container
+func TriggerBuilderGetProperty(appName string, key string) error {
+	if key != "selected" && key != "build-dir" {
+		return errors.New("Invalid logs property specified")
+	}
+
+	fmt.Println(common.PropertyGet("builder", appName, key))
+	return nil
+}
+
 // TriggerBuilderImageIsCNB prints true if an image is cnb based, false otherwise
 func TriggerBuilderImageIsCNB(appName string, image string) error {
 	if common.IsImageCnbBased(image) {