refactor: remove public exposure of DOKKU_APP_TYPE in favor of builder detected property

The DOKKU_APP_TYPE has long since ceased to be the correct way to specify the builder for the application. It's only usage has been during the detection phase, specifically to ensure that the herokuish plugin injects the correct docker arguments during the build. As such, it is safe to migrate away to a property in a patch release.

Users that seek to set a specific builder should use 'dokku builder:set $APP selected' instead.

Refs #7863

plugins/builder/triggers.go

@@ -27,14 +27,23 @@ func TriggerBuilderDetect(appName string) error {
 
 // 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")
+	if _, ok := DefaultProperties[key]; !ok {
+		return errors.New("Invalid builder property specified")
 	}
 
 	fmt.Println(common.PropertyGet("builder", appName, key))
 	return nil
 }
 
+// TriggerBuilderSetProperty writes the builder key to stdout for a given app container
+func TriggerBuilderSetProperty(appName string, key string, value string) error {
+	if _, ok := DefaultProperties[key]; !ok {
+		return errors.New("Invalid builder property specified")
+	}
+
+	return common.PropertyWrite("builder", appName, key, value)
+}
+
 // TriggerBuilderImageIsCNB prints true if an image is cnb based, false otherwise
 func TriggerBuilderImageIsCNB(appName string, image string) error {
 	if common.IsImageCnbBased(image) {
@@ -99,7 +108,30 @@ func TriggerInstall() error {
 		return fmt.Errorf("Unable to install the builder plugin: %s", err.Error())
 	}
 
-	_, err := common.CallPlugnTrigger(common.PlugnTriggerInput{
+	apps, err := common.UnfilteredDokkuApps()
+	if err != nil {
+		return nil
+	}
+
+	for _, appName := range apps {
+		if common.PropertyExists("builder", appName, "detected") {
+			continue
+		}
+
+		results, err := common.CallPlugnTrigger(common.PlugnTriggerInput{
+			Trigger: "config-get",
+			Args:    []string{appName, "DOKKU_APP_TYPE"},
+		})
+		if err != nil {
+			return err
+		}
+
+		if results.StdoutContents() != "" {
+			common.PropertyWrite("builder", appName, "detected", results.StdoutContents())
+		}
+	}
+
+	_, err = common.CallPlugnTrigger(common.PlugnTriggerInput{
 		Trigger: "install-builder-prune",
 	})