feat: infer package name from go.mod (#3827)

If all other strategies fail, try to infer the `package_name` property
from the `go.mod` file, using its last segment as the actual package
name.

This is not perfect, but usually this will only be used when running
against a new project, with no git url, empty/default config, etc... so,
in reality, it'll rarely be used.

closes #3825

Signed-off-by: Carlos A Becker <caarlos0@users.noreply.github.com>

internal/pipe/project/project.go

@@ -3,6 +3,8 @@ package project
 
 import (
 	"fmt"
+	"os/exec"
+	"strings"
 
 	"github.com/goreleaser/goreleaser/pkg/context"
 )
@@ -16,17 +18,40 @@ func (Pipe) String() string {
 
 // Default set project defaults.
 func (Pipe) Default(ctx *context.Context) error {
-	if ctx.Config.ProjectName == "" {
+	if ctx.Config.ProjectName != "" {
-		switch {
-		case ctx.Config.Release.GitHub.Name != "":
-			ctx.Config.ProjectName = ctx.Config.Release.GitHub.Name
-		case ctx.Config.Release.GitLab.Name != "":
-			ctx.Config.ProjectName = ctx.Config.Release.GitLab.Name
-		case ctx.Config.Release.Gitea.Name != "":
-			ctx.Config.ProjectName = ctx.Config.Release.Gitea.Name
-		default:
-			return fmt.Errorf("couldn't guess project_name, please add it to your config")
-		}
-	}
 		return nil
+	}
+
+	for _, candidate := range []string{
+		ctx.Config.Release.GitHub.Name,
+		ctx.Config.Release.GitLab.Name,
+		ctx.Config.Release.Gitea.Name,
+		moduleName(),
+	} {
+		if candidate == "" {
+			continue
+		}
+		ctx.Config.ProjectName = candidate
+		return nil
+	}
+
+	return fmt.Errorf("couldn't guess project_name, please add it to your config")
+}
+
+func moduleName() string {
+	bts, err := exec.Command("go", "list", "-m").CombinedOutput()
+	if err != nil {
+		return ""
+	}
+
+	mod := strings.TrimSpace(string(bts))
+
+	// this is the default module used when go runs without a go module.
+	// https://pkg.go.dev/cmd/go@master#hdr-Package_lists_and_patterns
+	if mod == "command-line-arguments" {
+		return ""
+	}
+
+	parts := strings.Split(mod, "/")
+	return strings.TrimSpace(parts[len(parts)-1])
 }

internal/pipe/project/project_test.go

@@ -1,15 +1,18 @@
 package project
 
 import (
+	"os/exec"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 
 	"github.com/goreleaser/goreleaser/internal/testctx"
+	"github.com/goreleaser/goreleaser/internal/testlib"
 	"github.com/goreleaser/goreleaser/pkg/config"
 )
 
 func TestCustomProjectName(t *testing.T) {
+	_ = testlib.Mktmp(t)
 	ctx := testctx.NewWithCfg(config.Project{
 		ProjectName: "foo",
 		Release: config.Release{
@@ -24,6 +27,7 @@ func TestCustomProjectName(t *testing.T) {
 }
 
 func TestEmptyProjectName_DefaultsToGitHubRelease(t *testing.T) {
+	_ = testlib.Mktmp(t)
 	ctx := testctx.NewWithCfg(config.Project{
 		Release: config.Release{
 			GitHub: config.Repo{
@@ -37,6 +41,7 @@ func TestEmptyProjectName_DefaultsToGitHubRelease(t *testing.T) {
 }
 
 func TestEmptyProjectName_DefaultsToGitLabRelease(t *testing.T) {
+	_ = testlib.Mktmp(t)
 	ctx := testctx.NewWithCfg(config.Project{
 		Release: config.Release{
 			GitLab: config.Repo{
@@ -50,6 +55,7 @@ func TestEmptyProjectName_DefaultsToGitLabRelease(t *testing.T) {
 }
 
 func TestEmptyProjectName_DefaultsToGiteaRelease(t *testing.T) {
+	_ = testlib.Mktmp(t)
 	ctx := testctx.NewWithCfg(config.Project{
 		Release: config.Release{
 			Gitea: config.Repo{
@@ -62,7 +68,16 @@ func TestEmptyProjectName_DefaultsToGiteaRelease(t *testing.T) {
 	require.Equal(t, "bar", ctx.Config.ProjectName)
 }
 
+func TestEmptyProjectName_DefaultsToGoModPath(t *testing.T) {
+	_ = testlib.Mktmp(t)
+	ctx := testctx.New()
+	require.NoError(t, exec.Command("go", "mod", "init", "github.com/foo/bar").Run())
+	require.NoError(t, Pipe{}.Default(ctx))
+	require.Equal(t, "bar", ctx.Config.ProjectName)
+}
+
 func TestEmptyProjectNameAndRelease(t *testing.T) {
+	_ = testlib.Mktmp(t)
 	ctx := testctx.NewWithCfg(config.Project{
 		Release: config.Release{
 			GitHub: config.Repo{},