entc/gen/internal: initial work for solving vcs conflicts (#851)

entc/gen/internal/vcs.go

@@ -0,0 +1,46 @@
+// Copyright 2019-present Facebook Inc. All rights reserved.
+// This source code is licensed under the Apache 2.0 license found
+// in the LICENSE file in the root directory of this source tree.
+
+package internal
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// CheckDir checks the given dir and reports if there are any VCS conflicts.
+func CheckDir(dir string) error {
+	return filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+		if info.IsDir() && dir != path {
+			return filepath.SkipDir
+		}
+		return checkFile(path)
+	})
+}
+
+// conflictMarker holds the default marker string for
+// both Git and Mercurial (default length is 7).
+const conflictMarker = "<<<<<<<"
+
+// checkFile checks the given file line by line
+// and reports if it contains any VCS conflicts.
+func checkFile(path string) error {
+	fi, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer fi.Close()
+
+	scan := bufio.NewScanner(fi)
+	scan.Split(bufio.ScanLines)
+	for i := 0; scan.Scan(); i++ {
+		if l := scan.Text(); strings.HasPrefix(l, conflictMarker) {
+			return fmt.Errorf("vcs conflict %s:%d", path, i+1)
+		}
+	}
+	return nil
+}

entc/gen/internal/vcs_test.go

@@ -0,0 +1,38 @@
+// Copyright 2019-present Facebook Inc. All rights reserved.
+// This source code is licensed under the Apache 2.0 license found
+// in the LICENSE file in the root directory of this source tree.
+
+package internal
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestCheckDir(t *testing.T) {
+	target := filepath.Join(os.TempDir(), "entvcs")
+	require.NoError(t, os.MkdirAll(target, os.ModePerm), "creating tmpdir")
+	defer os.RemoveAll(target)
+	err := ioutil.WriteFile(filepath.Join(target, "a.go"), []byte(`package schema`), 0644)
+	require.NoError(t, err)
+	err = ioutil.WriteFile(filepath.Join(target, "b.go"), []byte(`package schema
+
+type User struct {
+<<<<<<< local
+        ent.Schema
+=======
+        schema
+>>>>>>> other
+}
+`), 0644)
+	require.NoError(t, err)
+	err = CheckDir(target)
+	require.Error(t, err)
+	expected := fmt.Sprintf("vcs conflict %s/b.go:4", target)
+	require.EqualError(t, err, expected)
+}