refactor: using ast parser instead

Using the ast parser, so we don't need to glob and goreleaser will work
reliably even if the files aren't gofmt'd.

.gitignore

@@ -2,3 +2,4 @@ dist/
 vendor
 coverage.txt
 goreleaser
+debug.test

pipeline/build/build.go

@@ -4,7 +4,9 @@ package build
 
 import (
 	"fmt"
-	"io/ioutil"
+	"go/ast"
+	"go/parser"
+	"go/token"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -16,7 +18,6 @@ import (
 	"github.com/goreleaser/goreleaser/internal/buildtarget"
 	"github.com/goreleaser/goreleaser/internal/ext"
 	"github.com/goreleaser/goreleaser/internal/name"
-	zglob "github.com/mattn/go-zglob"
 	"github.com/pkg/errors"
 	"golang.org/x/sync/errgroup"
 )
@@ -44,25 +45,26 @@ func (Pipe) Run(ctx *context.Context) error {
 }
 
 func checkMain(ctx *context.Context, build config.Build) error {
-	var glob = build.Main
-	if !strings.HasSuffix(glob, "main.go") {
-		// TODO: in real live , glob will never be empty. Maybe this is worth
-		// guarding here anyway
-		glob = glob + "/" + "*.go"
+	var dir = strings.Replace(build.Main, "main.go", "", -1)
+	if dir == "" {
+		dir = "."
 	}
-	log.Debugf("glob is %s", glob)
-	files, err := zglob.Glob(glob)
+	packs, err := parser.ParseDir(token.NewFileSet(), dir, nil, 0)
 	if err != nil {
-		return errors.Wrap(err, "failed to find go files")
+		return errors.Wrapf(err, "failed dir: %s", dir)
 	}
-	log.WithField("files", files).Debug("go files")
-	for _, file := range files {
-		bts, err := ioutil.ReadFile(file)
-		if err != nil {
-			return errors.Wrapf(err, "failed to read file: %s", file)
-		}
-		if strings.Contains(string(bts), "func main() {") {
-			return nil
+	for _, pack := range packs {
+		for _, file := range pack.Files {
+			for _, decl := range file.Decls {
+				fn, ok := decl.(*ast.FuncDecl)
+				if !ok {
+					continue
+				}
+				log.Info(fn.Name.Name)
+				if fn.Name.Name == "main" && fn.Recv == nil {
+					return nil
+				}
+			}
 		}
 	}
 	return fmt.Errorf("build for %s does not contain a main function", build.Binary)

pipeline/build/build_test.go

@@ -234,35 +234,33 @@ func TestRunInvalidLdflags(t *testing.T) {
 }
 
 func TestRunPipeFailingHooks(t *testing.T) {
-	prepare := func() *context.Context {
-		folder, back := testlib.Mktmp(t)
-		defer back()
-		writeGoodMain(t, folder)
-		var config = config.Project{
-			Dist: folder,
-			Builds: []config.Build{
-				{
-					Main:   ".",
-					Binary: "hooks",
-					Hooks:  config.Hooks{},
-					Goos: []string{
-						runtime.GOOS,
-					},
-					Goarch: []string{
-						runtime.GOARCH,
-					},
+	folder, back := testlib.Mktmp(t)
+	defer back()
+	writeGoodMain(t, folder)
+	var config = config.Project{
+		Dist: folder,
+		Builds: []config.Build{
+			{
+				Binary: "hooks",
+				Hooks:  config.Hooks{},
+				Goos: []string{
+					runtime.GOOS,
+				},
+				Goarch: []string{
+					runtime.GOARCH,
 				},
 			},
-		}
-		return context.New(config)
+		},
 	}
 	t.Run("pre-hook", func(t *testing.T) {
-		var ctx = prepare()
+		var ctx = context.New(config)
 		ctx.Config.Builds[0].Hooks.Pre = "exit 1"
+		ctx.Config.Builds[0].Hooks.Post = "echo post"
 		assert.EqualError(t, Pipe{}.Run(ctx), `pre hook failed: `)
 	})
 	t.Run("post-hook", func(t *testing.T) {
-		var ctx = prepare()
+		var ctx = context.New(config)
+		ctx.Config.Builds[0].Hooks.Pre = "echo pre"
 		ctx.Config.Builds[0].Hooks.Post = "exit 1"
 		assert.EqualError(t, Pipe{}.Run(ctx), `post hook failed: `)
 	})
@@ -288,6 +286,10 @@ func TestRunPipeWithouMainFunc(t *testing.T) {
 		},
 	}
 	var ctx = context.New(config)
+	t.Run("empty", func(t *testing.T) {
+		ctx.Config.Builds[0].Main = ""
+		assert.EqualError(t, Pipe{}.Run(ctx), `build for no-main does not contain a main function`)
+	})
 	t.Run("glob", func(t *testing.T) {
 		ctx.Config.Builds[0].Main = "."
 		assert.EqualError(t, Pipe{}.Run(ctx), `build for no-main does not contain a main function`)
@@ -304,11 +306,11 @@ func exists(file string) bool {
 }
 
 func writeMainWithoutMainFunc(t *testing.T, folder string) {
-	writeFile(t, folder, "package main\nfunc notMain() {println(0)}")
+	writeFile(t, folder, "package main\nconst a = 2\nfunc notMain() {println(0)}")
 }
 
 func writeGoodMain(t *testing.T, folder string) {
-	writeFile(t, folder, "package main\nfunc main() {println(0)}")
+	writeFile(t, folder, "package main\nvar a = 1\nfunc main() {println(0)}")
 }
 
 func writeFile(t *testing.T, folder, content string) {