Add new fmtcmd package (linting)

hcl/fmtcmd/fmtcmd.go

@@ -0,0 +1,164 @@
+// Derivative work from:
+//	- https://golang.org/src/cmd/gofmt/gofmt.go
+//	- https://github.com/fatih/hclfmt
+
+package fmtcmd
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+
+	"github.com/hashicorp/hcl/hcl/printer"
+)
+
+var (
+	ErrWriteStdin = errors.New("cannot use write option with standard input")
+)
+
+type Options struct {
+	List  bool // list files whose formatting differs
+	Write bool // write result to (source) file instead of stdout
+	Diff  bool // display diffs instead of rewriting files
+}
+
+func isValidFile(f os.FileInfo, extensions []string) bool {
+	if !f.IsDir() && !strings.HasPrefix(f.Name(), ".") {
+		for _, ext := range extensions {
+			if strings.HasSuffix(f.Name(), "."+ext) {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+// If in == nil, the source is the contents of the file with the given filename.
+func processFile(filename string, in io.Reader, out io.Writer, stdin bool, opts Options) error {
+	if in == nil {
+		f, err := os.Open(filename)
+		if err != nil {
+			return err
+		}
+		defer f.Close()
+		in = f
+	}
+
+	src, err := ioutil.ReadAll(in)
+	if err != nil {
+		return err
+	}
+
+	res, err := printer.Format(src)
+	if err != nil {
+		return err
+	}
+	// Files should end with newlines
+	res = append(res, []byte("\n")...)
+
+	if !bytes.Equal(src, res) {
+		// formatting has changed
+		if opts.List {
+			fmt.Fprintln(out, filename)
+		}
+		if opts.Write {
+			err = ioutil.WriteFile(filename, res, 0644)
+			if err != nil {
+				return err
+			}
+		}
+		if opts.Diff {
+			data, err := diff(src, res)
+			if err != nil {
+				return fmt.Errorf("computing diff: %s", err)
+			}
+			fmt.Fprintf(out, "diff a/%s b/%s\n", filename, filename)
+			out.Write(data)
+		}
+	}
+
+	if !opts.List && !opts.Write && !opts.Diff {
+		_, err = out.Write(res)
+	}
+
+	return err
+}
+
+func walkDir(path string, extensions []string, stdout io.Writer, opts Options) error {
+	visitFile := func(path string, f os.FileInfo, err error) error {
+		if err == nil && isValidFile(f, extensions) {
+			err = processFile(path, nil, stdout, false, opts)
+		}
+		return err
+	}
+
+	return filepath.Walk(path, visitFile)
+}
+
+func Run(
+	paths, extensions []string,
+	stdin io.Reader,
+	stdout io.Writer,
+	opts Options,
+) error {
+	if len(paths) == 0 {
+		if opts.Write {
+			return ErrWriteStdin
+		}
+		if err := processFile("<standard input>", stdin, stdout, true, opts); err != nil {
+			return err
+		}
+		return nil
+	}
+
+	for _, path := range paths {
+		switch dir, err := os.Stat(path); {
+		case err != nil:
+			return err
+		case dir.IsDir():
+			if err := walkDir(path, extensions, stdout, opts); err != nil {
+				return err
+			}
+		default:
+			if err := processFile(path, nil, stdout, false, opts); err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+func diff(b1, b2 []byte) (data []byte, err error) {
+	f1, err := ioutil.TempFile("", "")
+	if err != nil {
+		return
+	}
+	defer os.Remove(f1.Name())
+	defer f1.Close()
+
+	f2, err := ioutil.TempFile("", "")
+	if err != nil {
+		return
+	}
+	defer os.Remove(f2.Name())
+	defer f2.Close()
+
+	f1.Write(b1)
+	f2.Write(b2)
+
+	data, err = exec.Command("diff", "-u", f1.Name(), f2.Name()).CombinedOutput()
+	if len(data) > 0 {
+		// diff exits with a non-zero status when the files don't match.
+		// Ignore that failure as long as we get output.
+		err = nil
+	}
+	return
+}