refactor: use github.com/pkg/errors (fix #240)

* Use `github.com/pkg/errors` instead of `errors`
* Use `errors.Wrap()` instead of constructing error message by `fmt.Errorf()` or string concatenation
* Use `errors.Errorf()` instead of `fmt.Errorf()`

Author: tyru

Gopkg.lock

@@ -1,9 +1,9 @@
 package config
 
 import (
-	"fmt"
-
 	"github.com/BurntSushi/toml"
+	"github.com/pkg/errors"
+
 	"github.com/vim-volt/volt/pathutil"
 )
 
@@ -80,7 +80,7 @@ func merge(cfg, initCfg *Config) {
 
 func validate(cfg *Config) error {
 	if cfg.Build.Strategy != "symlink" && cfg.Build.Strategy != "copy" {
-		return fmt.Errorf("build.strategy is %q: valid values are %q or %q", cfg.Build.Strategy, "symlink", "copy")
+		return errors.Errorf("build.strategy is %q: valid values are %q or %q", cfg.Build.Strategy, "symlink", "copy")
 	}
 	return nil
 }

config/config.go

@@ -31,9 +31,10 @@
 package fileutil
 
 import (
-	"fmt"
 	"os"
 	"syscall"
+
+	"github.com/pkg/errors"
 )
 
 // CopyFile copies the contents of the file named src to the file named
@@ -63,7 +64,7 @@ func CopyFile(src, dst string, buf []byte, perm os.FileMode) error {
 		for {
 			n, err := syscall.Sendfile(wfd, rfd, nil, readsize)
 			if err != nil {
-				return fmt.Errorf("sendfile(%q, %q) failed: %s", src, dst, err.Error())
+				return errors.Errorf("sendfile(%q, %q) failed: %s", src, dst, err.Error())
 			}
 			written += int64(n)
 			if written >= fi.Size() {
@@ -72,7 +73,7 @@ func CopyFile(src, dst string, buf []byte, perm os.FileMode) error {
 		}
 	} else {
 		if _, err := syscall.Sendfile(wfd, rfd, nil, int(fi.Size())); err != nil {
-			return fmt.Errorf("sendfile(%q, %q) failed: %s", src, dst, err.Error())
+			return errors.Errorf("sendfile(%q, %q) failed: %s", src, dst, err.Error())
 		}
 	}
 	return nil

fileutil/copyfile_linux.go

@@ -1,10 +1,10 @@
 package gitutil
 
 import (
-	"errors"
-	"fmt"
 	"regexp"
 
+	"github.com/pkg/errors"
+
 	"github.com/vim-volt/volt/pathutil"
 	git "gopkg.in/src-d/go-git.v4"
 	"gopkg.in/src-d/go-git.v4/plumbing"
@@ -109,7 +109,7 @@ func GetUpstreamRemote(r *git.Repository) (string, error) {
 	subsec := cfg.Raw.Section("branch").Subsection(branch[1])
 	remote := subsec.Option("remote")
 	if remote == "" {
-		return "", fmt.Errorf("gitconfig 'branch.%s.remote' is not found", subsec.Name)
+		return "", errors.Errorf("gitconfig 'branch.%s.remote' is not found", subsec.Name)
 	}
 	return remote, nil
 }

gitutil/gitutil.go

@@ -1,7 +1,7 @@
 package httputil
 
 import (
-	"errors"
+	"github.com/pkg/errors"
 	"io"
 	"io/ioutil"
 	"net/http"

httputil/httputil.go

@@ -1,8 +1,8 @@
 package testutil
 
 import (
-	"errors"
 	"fmt"
+	"github.com/pkg/errors"
 	"io/ioutil"
 	"os"
 	"os/exec"

internal/testutil/testutil.go

@@ -2,13 +2,13 @@ package lockjson
 
 import (
 	"encoding/json"
-	"errors"
-	"fmt"
 	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strconv"
 
+	"github.com/pkg/errors"
+
 	"github.com/vim-volt/volt/logger"
 	"github.com/vim-volt/volt/pathutil"
 )
@@ -112,19 +112,19 @@ func read(doLog bool) (*LockJSON, error) {
 	// Validate lock.json
 	err = validate(&lockJSON)
 	if err != nil {
-		return nil, errors.New("validation failed: lock.json: " + err.Error())
+		return nil, errors.Wrap(err, "validation failed: lock.json")
 	}
 
 	return &lockJSON, nil
 }
 
 func validate(lockJSON *LockJSON) error {
 	if lockJSON.Version < 1 {
-		return fmt.Errorf("lock.json version is '%d' (must be 1 or greater)", lockJSON.Version)
+		return errors.Errorf("lock.json version is '%d' (must be 1 or greater)", lockJSON.Version)
 	}
 	// Validate if volt can manipulate lock.json of this version
 	if lockJSON.Version > lockJSONVersion {
-		return fmt.Errorf("this lock.json version is '%d' which volt cannot recognize. please upgrade volt to process this file", lockJSON.Version)
+		return errors.Errorf("this lock.json version is '%d' which volt cannot recognize. please upgrade volt to process this file", lockJSON.Version)
 	}
 
 	// Validate if missing required keys exist

lockjson/lockjson.go

@@ -1,7 +1,7 @@
 package pathutil
 
 import (
-	"errors"
+	"github.com/pkg/errors"
 	"os"
 	"os/exec"
 	"path/filepath"

pathutil/pathutil.go

@@ -3,7 +3,6 @@ package plugconf
 import (
 	"bytes"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"io/ioutil"
 	"path"
@@ -12,6 +11,8 @@ import (
 	"sort"
 	"strings"
 
+	"github.com/pkg/errors"
+
 	multierror "github.com/hashicorp/go-multierror"
 	"github.com/vim-volt/volt/httputil"
 	"github.com/vim-volt/volt/lockjson"
@@ -392,7 +393,7 @@ func ParsePlugconf(file *ast.File, src []byte, path string) (*ParsedInfo, *Parse
 			}
 		case isProhibitedFuncName(ident.Name):
 			parseErr.merr = multierror.Append(parseErr.merr,
-				fmt.Errorf(
+				errors.Errorf(
 					"'%s' is prohibited function name. please use other function name", ident.Name))
 		default:
 			functions = append(functions, string(extractBody(fn, src)))

plugconf/plugconf.go

@@ -1,14 +1,15 @@
 package builder
 
 import (
-	"errors"
 	"fmt"
 	"io"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"strings"
 
+	"github.com/pkg/errors"
+
 	"github.com/hashicorp/go-multierror"
 	"github.com/vim-volt/volt/fileutil"
 	"github.com/vim-volt/volt/lockjson"
@@ -79,7 +80,7 @@ func (builder *BaseBuilder) installRCFile(profileName, srcRCFileName, dst string
 			if !pathutil.Exists(src) {
 				return nil
 			}
-			return fmt.Errorf("'%s' is not an auto-generated file. please move to '%s' and re-run 'volt build'", dst, pathutil.RCDir(profileName))
+			return errors.Errorf("'%s' is not an auto-generated file. please move to '%s' and re-run 'volt build'", dst, pathutil.RCDir(profileName))
 		}
 	}
 
@@ -175,7 +176,7 @@ func (builder *BaseBuilder) helptags(reposPath pathutil.ReposPath, vimExePath st
 	logger.Debugf("Executing '%s %s' ...", vimExePath, strings.Join(vimArgs, " "))
 	err := exec.Command(vimExePath, vimArgs...).Run()
 	if err != nil {
-		return errors.New("failed to make tags file: " + err.Error())
+		return errors.Wrap(err, "failed to make tags file")
 	}
 	return nil
 }