cmd/cue: get the working directory once at init time

This way we don't have to get it separately in multiple places,
particularly each time that we print an error.

Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: I305744a3984a832566a6c70a47dfd24152f3759e
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1195084
Reviewed-by: Roger Peppe <rogpeppe@gmail.com>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>

cmd/cue/cmd/cmd.go

@@ -16,7 +16,6 @@ package cmd
 
 import (
 	"fmt"
-	"os"
 
 	"cuelang.org/go/cue/errors"
 	"github.com/spf13/cobra"
@@ -164,8 +163,7 @@ Run "cue help commands" for more details on tasks and workflow commands.
 				if !isRootCmd {
 					cmdline += " cmd"
 				}
-				cwd, _ := os.Getwd()
-				fmt.Fprint(w, errors.Details(err, &errors.Config{Cwd: cwd}))
+				fmt.Fprint(w, errors.Details(err, &errors.Config{Cwd: rootWorkingDir}))
 				fmt.Fprintln(w, `Ensure custom commands are defined in a "_tool.cue" file.`)
 				fmt.Fprintln(w, "Run 'cue help cmd' to list available custom commands.")
 				if isRootCmd {

cmd/cue/cmd/fix.go

@@ -49,11 +49,6 @@ Without any packages, fix applies to all files within a module.
 }
 
 func runFixAll(cmd *Command, args []string) error {
-	dir, err := os.Getwd()
-	if err != nil {
-		return err
-	}
-
 	var opts []fix.Option
 	if flagSimplify.Bool(cmd) {
 		opts = append(opts, fix.Simplify())
@@ -62,6 +57,7 @@ func runFixAll(cmd *Command, args []string) error {
 	if len(args) == 0 {
 		args = []string{"./..."}
 
+		dir := rootWorkingDir
 		for {
 			if _, err := os.Stat(filepath.Join(dir, "cue.mod")); err == nil {
 				args = appendDirs(args, filepath.Join(dir, "cue.mod", "gen"))

cmd/cue/cmd/fmt.go

@@ -49,7 +49,6 @@ Directories named "cue.mod" and those beginning with "." and "_" are skipped unl
 given as explicit arguments.
 `,
 		RunE: mkRunE(c, func(cmd *Command, args []string) error {
-			cwd, _ := os.Getwd()
 			check := flagCheck.Bool(cmd)
 			doDiff := flagDiff.Bool(cmd)
 
@@ -86,7 +85,7 @@ given as explicit arguments.
 							continue
 						}
 
-						wasModified, err := formatFile(file, formatOpts, cwd, doDiff, check, cmd)
+						wasModified, err := formatFile(file, formatOpts, doDiff, check, cmd)
 						if err != nil {
 							return err
 						}
@@ -121,7 +120,7 @@ given as explicit arguments.
 						file.Source = contents
 					}
 
-					wasModified, err := formatFile(file, formatOpts, cwd, doDiff, check, cmd)
+					wasModified, err := formatFile(file, formatOpts, doDiff, check, cmd)
 					if err != nil {
 						return err
 					}
@@ -182,7 +181,7 @@ given as explicit arguments.
 
 // formatFile formats a single file.
 // It returns true if the file was not well formatted.
-func formatFile(file *build.File, opts []format.Option, cwd string, doDiff, check bool, cmd *Command) (bool, error) {
+func formatFile(file *build.File, opts []format.Option, doDiff, check bool, cmd *Command) (bool, error) {
 	// We buffer the input and output bytes to compare them.
 	// This allows us to determine whether a file is already
 	// formatted, without modifying the file.
@@ -216,7 +215,7 @@ func formatFile(file *build.File, opts []format.Option, cwd string, doDiff, chec
 		return false, nil
 	}
 
-	path, err := filepath.Rel(cwd, file.Filename)
+	path, err := filepath.Rel(rootWorkingDir, file.Filename)
 	if err != nil {
 		path = file.Filename
 	}

cmd/cue/cmd/modget.go

@@ -107,10 +107,7 @@ func runModGet(cmd *Command, args []string) error {
 func findModuleRoot() (string, error) {
 	// TODO this logic is duplicated in multiple places. We should
 	// consider deduplicating it.
-	dir, err := os.Getwd()
-	if err != nil {
-		return "", err
-	}
+	dir := rootWorkingDir
 	for {
 		if _, err := os.Stat(filepath.Join(dir, "cue.mod")); err == nil {
 			return dir, nil

cmd/cue/cmd/modinit.go

@@ -71,12 +71,7 @@ func runModInit(cmd *Command, args []string) (err error) {
 		}
 	}
 
-	cwd, err := os.Getwd()
-	if err != nil {
-		return err
-	}
-
-	mod := filepath.Join(cwd, "cue.mod")
+	mod := filepath.Join(rootWorkingDir, "cue.mod")
 	if info, err := os.Stat(mod); err == nil {
 		if !info.IsDir() {
 			return fmt.Errorf("cue.mod files are no longer supported; use cue.mod/module.cue")

cmd/cue/cmd/root.go

@@ -267,14 +267,25 @@ For more information on writing CUE configuration files see cuelang.org.`,
 
 var rootContextOptions []cuecontext.Option
 
+// rootWorkingDir avoids repeated calls to [os.Getwd] in cmd/cue.
+// If we can't figure out the current directory, something is very wrong,
+// and there's no point in continuing to run a command.
+var rootWorkingDir = func() string {
+	wd, err := os.Getwd()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "cannot get current directory: %v\n", err)
+		os.Exit(1)
+	}
+	return wd
+}()
+
 // Main runs the cue tool and returns the code for passing to os.Exit.
 func Main() int {
 	cmd, _ := New(os.Args[1:])
 	if err := cmd.Run(backgroundContext()); err != nil {
 		if err != ErrPrintedError {
-			cwd, _ := os.Getwd()
 			errors.Print(os.Stderr, err, &errors.Config{
-				Cwd:     cwd,
+				Cwd:     rootWorkingDir,
 				ToSlash: testing.Testing(),
 			})
 		}
@@ -350,12 +361,9 @@ func printError(cmd *Command, err error) {
 	format := func(w io.Writer, format string, args ...interface{}) {
 		p.Fprintf(w, format, args...)
 	}
-
-	// TODO(mvdan): call os.Getwd only once at the start of the process.
-	cwd, _ := os.Getwd()
 	errors.Print(cmd.Stderr(), err, &errors.Config{
 		Format:  format,
-		Cwd:     cwd,
+		Cwd:     rootWorkingDir,
 		ToSlash: testing.Testing(),
 	})
 }