feat(copier): add the -dir flag (#14)

README.md

@@ -5,7 +5,7 @@
 [![goreportcard](https://goreportcard.com/badge/go-simpler.org/assert)](https://goreportcard.com/report/go-simpler.org/assert)
 [![codecov](https://codecov.io/gh/go-simpler/assert/branch/main/graph/badge.svg)](https://codecov.io/gh/go-simpler/assert)
 
-Common assertions to use with the standard testing package
+Common assertions to use with the standard `testing` package
 
 ## 📌 About
 
@@ -30,7 +30,7 @@ There is also a special tool to do this automatically:
 just add the following directive to any `.go` file and run `go generate ./...`:
 
 ```go
-//go:generate go run -tags=copier go-simpler.org/assert/cmd/copier@latest .
+//go:generate go run -tags=copier go-simpler.org/assert/cmd/copier@latest
 ```
 
 See the `cmd/copier` documentation for details.

cmd/copier/main.go

@@ -3,18 +3,14 @@
 // Copier is a convenience tool that copies the assertions into a project,
 // so that they can be used without introducing a direct dependency.
 //
-// Add the following directive to any .go file and run `go generate ./...`:
-//
-//	go:generate go run -tags=copier go-simpler.org/assert/cmd/copier@latest <path/to/pkg>
-//
-// Where <path/to/pkg> is the location where you want to put the generated package,
-// e.g. `.` for the project root (hint: for libraries you may want to put it in `internal`).
+// Usage: //go:generate go run -tags=copier go-simpler.org/assert/cmd/copier@<version> [-dir=<working-directory>]
 package main
 
 import (
 	"context"
 	"encoding/json"
 	"errors"
+	"flag"
 	"fmt"
 	"os"
 	"os/exec"
@@ -36,36 +32,37 @@ func main() {
 }
 
 func run(ctx context.Context) error {
-	if len(os.Args) < 2 {
-		return errors.New("path to package is not specified")
+	var workDir string
+
+	fs := flag.NewFlagSet(os.Args[0], flag.ContinueOnError)
+	fs.StringVar(&workDir, "dir", ".", "the working directory")
+	if err := fs.Parse(os.Args[1:]); err != nil {
+		return fmt.Errorf("parsing flags: %w", err)
 	}
 
 	moduleName, err := readModuleName(ctx)
 	if err != nil {
 		return err
 	}
 
-	path := filepath.Join(os.Args[1], "assert")
-	fullpath := filepath.Join(path, "EF")
-
-	if err := os.MkdirAll(fullpath, 0755); err != nil && !errors.Is(err, os.ErrExist) {
-		return err
-	}
-	if err := os.Chdir(path); err != nil {
-		return err
+	importPath := filepath.Join(moduleName, "assert")
+	if workDir != "." {
+		importPath = filepath.Join(moduleName, workDir, "assert")
 	}
+	assert.AliasFile = strings.Replace(assert.AliasFile, "go-simpler.org/assert", importPath, 1)
 
-	importPath := moduleName
-	if path != "." {
-		importPath = filepath.Join(moduleName, path)
+	dirPath := filepath.Join(workDir, "assert", "EF")
+	if err := os.MkdirAll(dirPath, 0755); err != nil && !errors.Is(err, os.ErrExist) {
+		return err
 	}
 
-	aliasFile := strings.Replace(assert.AliasFile, "go-simpler.org/assert", importPath, 1)
-
-	if err := writeFile("assert.go", assert.MainFile); err != nil {
+	mainPath := filepath.Join(workDir, "assert", "assert.go")
+	if err := writeFile(mainPath, assert.MainFile); err != nil {
 		return err
 	}
-	if err := writeFile("EF/alias.go", aliasFile); err != nil {
+
+	aliasPath := filepath.Join(workDir, "assert", "EF", "alias.go")
+	if err := writeFile(aliasPath, assert.AliasFile); err != nil {
 		return err
 	}
 
@@ -96,19 +93,13 @@ func readModuleName(ctx context.Context) (string, error) {
 	return info.Module.Path, nil
 }
 
-func writeFile(name, content string) error {
-	f, err := os.Create(name)
-	if err != nil {
-		return err
-	}
-	defer f.Close()
-
+func writeFile(path, content string) error {
 	const header = `// This Source Code Form is subject to the terms of the Mozilla Public
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at https://mozilla.org/MPL/2.0/.
 
 // Code generated by go-simpler.org/assert/cmd/copier. DO NOT EDIT.
 
 `
-	return os.WriteFile(name, []byte(header+content), 0644)
+	return os.WriteFile(path, []byte(header+content), 0644)
 }

embed.go

@@ -4,7 +4,7 @@ package assert
 
 import _ "embed"
 
-// These files are used by the `cmd/copier` tool. Ignore them.
+// These files are used by the cmd/copier tool. Ignore them.
 var (
 	//go:embed assert.go
 	MainFile string