Add support for including nodejs at runtime

[fgrehm]

Slack thread

Describe the Enhancement

We'd like to be able to use nodejs at runtime by flipping an env var from our project.tomls

Possible Solution

I've implemented a very simple buildpack that enables nodejs at runtime by setting BP_INCLUDE_NODEJS_RUNTIME=true

detect.go click to see

package nodejsruntime

import (
	"fmt"
	"os"
	"path/filepath"

	"github.com/paketo-buildpacks/packit/v2"
	"github.com/paketo-buildpacks/packit/v2/fs"
	"github.com/paketo-buildpacks/packit/v2/scribe"
)

var nodeRequirement = packit.BuildPlanRequirement{
	Name: "node",
	Metadata: map[string]interface{}{
		"launch": true,
	},
}

var nodeModulesRequirement = packit.BuildPlanRequirement{
	Name: "node_modules",
	Metadata: map[string]interface{}{
		"launch": true,
	},
}

func Detect(logger scribe.Emitter) packit.DetectFunc {
	return func(context packit.DetectContext) (packit.DetectResult, error) {
		logger.Debug.Title("%s %s", context.BuildpackInfo.ID, context.BuildpackInfo.Version)
		if os.Getenv("BP_INCLUDE_NODEJS_RUNTIME") != "true" {
			return packit.DetectResult{}, packit.Fail.WithMessage("BP_INCLUDE_NODEJS_RUNTIME is not set to true")
		}
		logger.Debug.Process("NodeJS is wanted for runtime")

		buildPlan := packit.BuildPlan{
			Requires: []packit.BuildPlanRequirement{nodeRequirement},
		}

		hasPackageJSON, err := fs.Exists(filepath.Join(context.WorkingDir, "package.json"))
		if err != nil {
			return packit.DetectResult{}, fmt.Errorf("failed to check for package.json: %w", err)
		} else if hasPackageJSON {
			logger.Debug.Process("node_modules is wanted for runtime")
			buildPlan.Requires = []packit.BuildPlanRequirement{nodeRequirement, nodeModulesRequirement}
			buildPlan.Or = []packit.BuildPlan{{
				Requires: []packit.BuildPlanRequirement{nodeRequirement},
			}}
		}

		return packit.DetectResult{
			Plan: buildPlan,
		}, nil
	}
}

build.go click to see

package nodejsruntime

import (
	"os"

	"github.com/paketo-buildpacks/packit/v2"
	"github.com/paketo-buildpacks/packit/v2/scribe"
)

func Build(logger scribe.Emitter) packit.BuildFunc {
	return func(context packit.BuildContext) (packit.BuildResult, error) {
		if os.Getenv("BP_INCLUDE_NODEJS_RUNTIME") == "true" {
			logger.Title("%s %s", context.BuildpackInfo.ID, context.BuildpackInfo.Version)
			logger.Process("NodeJS was configured for execution at runtime")
		}
		return packit.BuildResult{}, nil
	}
}

Motivation

We have a Rails application that uses nodejs for both asset compilation and also at runtime. The use case is to interact with browserless.io with nodejs scripts / pkgs.

I haven't tested but right now the only way to get nodejs at runtime is probably to mix the full nodejs buildpack with the ruby one in a group and also do something to trigger one of the nodejs *-start buildpacks.

[josegonzalez]

I ended up adding https://github.com/paketo-community/build-plan as a buildpack group to my project.toml and the following plan.toml in my source to get nodejs at runtime:

[[requires]]
    name = "node"
    version = "~16"

    [requires.metadata]
        launch = true