support multi-path gopath (#435)

Support multi-path gopaths.

mockgen/parse.go

@@ -641,13 +641,16 @@ func parsePackageImport(srcDir string) (string, error) {
 		}
 	}
 	// fall back to GOPATH mode
-	goPath := os.Getenv("GOPATH")
-	if goPath == "" {
+	goPaths := os.Getenv("GOPATH")
+	if goPaths == "" {
 		return "", fmt.Errorf("GOPATH is not set")
 	}
-	sourceRoot := filepath.Join(goPath, "src") + string(os.PathSeparator)
-	if !strings.HasPrefix(srcDir, sourceRoot) {
-		return "", errOutsideGoPath
+	goPathList := strings.Split(goPaths, string(os.PathListSeparator))
+	for _, goPath := range goPathList {
+		sourceRoot := filepath.Join(goPath, "src") + string(os.PathSeparator)
+		if strings.HasPrefix(srcDir, sourceRoot) {
+			return filepath.ToSlash(strings.TrimPrefix(srcDir, sourceRoot)), nil
+		}
 	}
-	return filepath.ToSlash(strings.TrimPrefix(srcDir, sourceRoot)), nil
+	return "", errOutsideGoPath
 }

mockgen/parse_test.go

@@ -7,6 +7,7 @@ import (
 	"io/ioutil"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 )
 
@@ -202,3 +203,45 @@ func TestParsePackageImport_FallbackGoPath(t *testing.T) {
 		t.Errorf("expect %s, got %s", expected, pkgPath)
 	}
 }
+
+func TestParsePackageImport_FallbackMultiGoPath(t *testing.T) {
+	var goPathList []string
+
+	// first gopath
+	goPath, err := ioutil.TempDir("", "gopath1")
+	if err != nil {
+		t.Error(err)
+	}
+	goPathList = append(goPathList, goPath)
+	defer func() {
+		if err = os.RemoveAll(goPath); err != nil {
+			t.Error(err)
+		}
+	}()
+	srcDir := filepath.Join(goPath, "src/example.com/foo")
+	err = os.MkdirAll(srcDir, 0755)
+	if err != nil {
+		t.Error(err)
+	}
+
+	// second gopath
+	goPath, err = ioutil.TempDir("", "gopath2")
+	if err != nil {
+		t.Error(err)
+	}
+	goPathList = append(goPathList, goPath)
+	defer func() {
+		if err = os.RemoveAll(goPath); err != nil {
+			t.Error(err)
+		}
+	}()
+
+	goPaths := strings.Join(goPathList, string(os.PathListSeparator))
+	os.Setenv("GOPATH", goPaths)
+	os.Setenv("GO111MODULE", "on")
+	pkgPath, err := parsePackageImport(srcDir)
+	expected := "example.com/foo"
+	if pkgPath != expected {
+		t.Errorf("expect %s, got %s", expected, pkgPath)
+	}
+}