Implements go build compilation process

Implementation of #3.

Signed-off-by: Timothy Hitchener <thitchener@vmware.com>
Signed-off-by: Ryan Moran <rmoran@vmware.com>
Signed-off-by: Sophie Wigmore <swigmore@vmware.com>

.github/util/tag.sh

@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+
+set -eu
+set -o pipefail
+
+function main() {
+  local previous tag
+  previous="$(git describe --tags "$(git rev-list --tags --max-count=1)")"
+  tag="$(printf "%s" "$previous" | awk -F. '{$NF = $NF + 1;} 1' | sed 's/ /./g')"
+
+  printf "v%s" "${tag#v}"
+}
+
+main "${@:-}"

.github/workflows/create-release.yml

@@ -0,0 +1,94 @@
+name: Create Release
+
+on:
+  push:
+    branches:
+    - master
+
+jobs:
+  unit:
+    name: Unit Tests
+    runs-on: ubuntu-latest
+    steps:
+    - name: Setup Go
+      uses: actions/setup-go@v1
+      with:
+        go-version: 1.14
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Run Unit Tests
+      run: ./scripts/unit.sh
+
+  integration:
+    name: Integration Tests
+    runs-on: ubuntu-latest
+    needs: unit
+    steps:
+    - name: Setup Go
+      uses: actions/setup-go@v1
+      with:
+        go-version: 1.14
+    - name: Checkout
+      uses: actions/checkout@v2
+    - run: git fetch --depth=1 origin +refs/tags/*:refs/tags/*
+    - name: Run Integration Tests
+      run: ./scripts/integration.sh
+      env:
+        GIT_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  release:
+    name: Release
+    runs-on: ubuntu-latest
+    needs: integration
+    steps:
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Tag
+      id: tag
+      run: |
+        git fetch --depth=1 origin +refs/tags/*:refs/tags/*
+        TAG="$(./.github/util/tag.sh)"
+        echo "::set-output name=tag::$TAG"
+    - name: Package
+      env:
+        TAG: ${{ steps.tag.outputs.tag }}
+      run: PACKAGE_DIR=artifact ./scripts/package.sh --version "${TAG}" --archive
+    - name: Create Release Notes
+      id: create-release-notes
+      run: |
+        mkdir -p "${HOME}/bin"
+        export PATH="${PATH}:${HOME}/bin"
+        curl "https://github.com/cloudfoundry/packit/releases/download/v0.0.4/jam-linux" \
+          --silent \
+          --location \
+          --output "${HOME}/bin/jam"
+        chmod +x "${HOME}/bin/jam"
+        RELEASE_BODY=$(jam summarize --buildpack "${PWD}/artifact.tgz" --format markdown)
+        # Coz of this messed up issue
+        # https://github.community/t5/GitHub-Actions/set-output-Truncates-Multiline-Strings/m-p/38372#M3322
+        RELEASE_BODY="${RELEASE_BODY//'%'/'%25'}"
+        RELEASE_BODY="${RELEASE_BODY//$'\n'/'%0A'}"
+        RELEASE_BODY="${RELEASE_BODY//$'\r'/'%0D'}"
+        echo "::set-output name=release_body::$RELEASE_BODY"
+    - name: Create Release
+      id: create-release
+      uses: actions/create-release@v1
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      with:
+        tag_name: ${{ steps.tag.outputs.tag }}
+        release_name: ${{ steps.tag.outputs.tag }}
+        body: ${{ steps.create-release-notes.outputs.release_body }}
+        draft: false
+        prerelease: false
+    - name: Upload Release Asset
+      id: upload-release-asset
+      uses: actions/upload-release-asset@v1
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      with:
+        upload_url: ${{ steps.create-release.outputs.upload_url }} # This pulls from the CREATE RELEASE step above, referencing it's ID to get its outputs object, which include a `upload_url`. See this blog post for more info: https://jasonet.co/posts/new-features-of-github-actions/#passing-data-to-future-steps
+        asset_path: artifact.tgz
+        asset_name: ${{ github.event.repository.name }}-${{ steps.tag.outputs.tag }}.tgz
+        asset_content_type: application/gzip
+

.github/workflows/receive-github-config-updates.yml

@@ -0,0 +1,35 @@
+name: Sync
+
+on:
+  repository_dispatch:
+    types: working-dir-update
+
+jobs:
+  build:
+    name: Sync
+    runs-on: ubuntu-latest
+    steps:
+
+    # checkout paketo github-config as src-repo
+    - name: Checkout paketo github-config repo
+      uses: actions/checkout@v2
+      with:
+        repository: paketo-buildpacks/github-config
+        path: config-repo
+
+    # checkout this repo
+    - name: Checkout
+      uses: actions/checkout@v2
+      with:
+        path: current-repo
+
+    - name: Run the sync action
+      uses: paketo-buildpacks/github-config/actions/sync@master
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      with:
+        config-repo: config-repo
+        current-repo: current-repo
+        config-path: "/implementation"
+        ssh-private-key: ${{ secrets.PAKETO_BOT_SSH_KEY }}
+      id: do-sync

.github/workflows/test-pull-request.yml

@@ -0,0 +1,37 @@
+name: Test Pull Request
+
+on:
+  pull_request:
+    branches:
+    - master
+
+jobs:
+  unit:
+    name: Unit Tests
+    runs-on: ubuntu-latest
+    steps:
+    - name: Setup Go
+      uses: actions/setup-go@v1
+      with:
+        go-version: 1.14
+    - name: Checkout
+      uses: actions/checkout@v2
+    - name: Run Unit Tests
+      run: ./scripts/unit.sh
+
+  integration:
+    name: Integration Tests
+    runs-on: ubuntu-latest
+    needs: unit
+    steps:
+    - name: Setup Go
+      uses: actions/setup-go@v1
+      with:
+        go-version: 1.14
+    - name: Checkout
+      uses: actions/checkout@v2
+    - run: git fetch --depth=1 origin +refs/tags/*:refs/tags/*
+    - name: Run Integration Tests
+      run: ./scripts/integration.sh
+      env:
+        GIT_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.gitignore

@@ -0,0 +1 @@
+/.bin

build.go

@@ -0,0 +1,115 @@
+package gobuild
+
+import (
+	"errors"
+	"path/filepath"
+	"time"
+
+	"github.com/paketo-buildpacks/packit"
+	"github.com/paketo-buildpacks/packit/chronos"
+)
+
+//go:generate faux --interface BuildProcess --output fakes/build_process.go
+type BuildProcess interface {
+	Execute(workspace, output, goPath, goCache string, targets []string) (command string, err error)
+}
+
+//go:generate faux --interface PathManager --output fakes/path_manager.go
+type PathManager interface {
+	Setup(workspace string) (goPath, path string, err error)
+	Teardown(goPath string) error
+}
+
+//go:generate faux --interface ChecksumCalculator --output fakes/checksum_calculator.go
+type ChecksumCalculator interface {
+	Sum(path string) (sha string, err error)
+}
+
+//go:generate faux --interface SourceRemover --output fakes/source_remover.go
+type SourceRemover interface {
+	Clear(path string) error
+}
+
+func Build(
+	buildProcess BuildProcess,
+	pathManager PathManager,
+	clock chronos.Clock,
+	checksumCalculator ChecksumCalculator,
+	logs LogEmitter,
+	parser TargetsParser,
+	sourceRemover SourceRemover,
+) packit.BuildFunc {
+
+	return func(context packit.BuildContext) (packit.BuildResult, error) {
+		logs.Title("%s %s", context.BuildpackInfo.Name, context.BuildpackInfo.Version)
+
+		targetsLayer, err := context.Layers.Get(TargetsLayerName, packit.LaunchLayer)
+		if err != nil {
+			return packit.BuildResult{}, err
+		}
+
+		goCacheLayer, err := context.Layers.Get(GoCacheLayerName, packit.CacheLayer)
+		if err != nil {
+			return packit.BuildResult{}, err
+		}
+
+		checksum, err := checksumCalculator.Sum(context.WorkingDir)
+		if err != nil {
+			return packit.BuildResult{}, err
+		}
+
+		previousSum, _ := targetsLayer.Metadata[WorkspaceSHAKey].(string)
+		if checksum != previousSum {
+			targets, err := parser.Parse(filepath.Join(context.WorkingDir, "buildpack.yml"))
+			if err != nil {
+				return packit.BuildResult{}, err
+			}
+
+			goPath, path, err := pathManager.Setup(context.WorkingDir)
+			if err != nil {
+				return packit.BuildResult{}, err
+			}
+
+			command, err := buildProcess.Execute(path, filepath.Join(targetsLayer.Path, "bin"), goPath, goCacheLayer.Path, targets)
+			if err != nil {
+				return packit.BuildResult{}, err
+			}
+
+			err = pathManager.Teardown(goPath)
+			if err != nil {
+				return packit.BuildResult{}, err
+			}
+
+			targetsLayer.Metadata = map[string]interface{}{
+				WorkspaceSHAKey: checksum,
+				"built_at":      clock.Now().Format(time.RFC3339Nano),
+				"command":       command,
+			}
+		}
+
+		command, ok := targetsLayer.Metadata["command"].(string)
+		if !ok {
+			return packit.BuildResult{}, errors.New("failed to identify start command from reused layer metadata")
+		}
+
+		err = sourceRemover.Clear(context.WorkingDir)
+		if err != nil {
+			return packit.BuildResult{}, err
+		}
+
+		logs.Process("Assigning launch processes")
+		logs.Subprocess("web: %s", command)
+
+		return packit.BuildResult{
+			Plan:   context.Plan,
+			Layers: []packit.Layer{targetsLayer, goCacheLayer},
+			Processes: []packit.Process{
+				{
+					Type:    "web",
+					Command: command,
+					Direct:  context.Stack == TinyStackName,
+				},
+			},
+		}, nil
+	}
+}

build_targets_parser.go

@@ -0,0 +1,53 @@
+package gobuild
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"gopkg.in/yaml.v2"
+)
+
+type BuildTargetsParser struct{}
+
+func NewBuildTargetsParser() BuildTargetsParser {
+	return BuildTargetsParser{}
+}
+
+func (p BuildTargetsParser) Parse(path string) ([]string, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		if errors.Is(err, os.ErrNotExist) {
+			return []string{"."}, nil
+		}
+
+		return nil, fmt.Errorf("failed to read buildpack.yml: %w", err)
+	}
+
+	var config struct {
+		Go struct {
+			Targets []string `yaml:"targets"`
+		} `yaml:"go"`
+	}
+
+	err = yaml.NewDecoder(file).Decode(&config)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode buildpack.yml: %w", err)
+	}
+
+	if len(config.Go.Targets) == 0 {
+		return []string{"."}, nil
+	}
+
+	for index, target := range config.Go.Targets {
+		if strings.HasPrefix(target, string(filepath.Separator)) {
+			return nil, fmt.Errorf("failed to determine build targets: %q is an absolute path, targets must be relative to the source directory", target)
+		}
+
+		config.Go.Targets[index] = fmt.Sprintf("./%s", filepath.Clean(target))
+	}
+
+	return config.Go.Targets, nil
+}