Rename CopyIfChanged to WriteIfNeeded and clarify comments

internal/file/file.go

@@ -8,9 +8,10 @@ import (
 	"os"
 )
 
-// CopyIfChanged copies source data to a destination filename if it has changed.
-func CopyIfChanged(destFilename string, source []byte, perm os.FileMode) error {
-	matches, err := probablyMatches(destFilename, source)
+// WriteIfNeeded writes data to a destination file, only if the file does not exist or if it was partially written.
+// To save time, it only checks that the file size is correct, and then matches the end of its contents (up to 32KB).
+func WriteIfNeeded(destFilename string, source []byte, perm os.FileMode) error {
+	matches, err := probablyMatches(destFilename, source, 32*1024)
 	if err != nil || matches {
 		return err
 	}
@@ -27,9 +28,8 @@ func Write(path string, content []byte, fileMode fs.FileMode) error {
 	return os.Rename(tmpFile, path)
 }
 
-// probablyMatches checks, heuristically, if a file matches source data.
-// To save time, it only compares the file size and the end of its contents (up to 32KB).
-func probablyMatches(filename string, data []byte) (bool, error) {
+// probablyMatches checks if a file exists and matches the end of source data (up to checkSize bytes).
+func probablyMatches(filename string, data []byte, checkSize int) (bool, error) {
 	f, err := os.Open(filename)
 	if err != nil {
 		if errors.Is(err, fs.ErrNotExist) {
@@ -47,7 +47,7 @@ func probablyMatches(filename string, data []byte) (bool, error) {
 		return false, nil
 	}
 
-	return matchEndOfFile(f, data, 32*1024)
+	return matchEndOfFile(f, data, checkSize)
 }
 
 func matchEndOfFile(f *os.File, b []byte, size int) (bool, error) {

internal/file/file_test.go

@@ -11,7 +11,7 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func TestCopyIfChanged(t *testing.T) {
+func TestWriteIfNeeded(t *testing.T) {
 	largeContentLength := 128 * 1024
 	largeContent := make([]byte, largeContentLength)
 	largeContent[0] = 'f'
@@ -50,24 +50,26 @@ func TestCopyIfChanged(t *testing.T) {
 				time.Sleep(time.Millisecond * 5)
 			}
 
-			var modTimeBeforeCopy time.Time
+			var modTimeBefore time.Time
 			stat, err := os.Stat(destFile)
 			if c.initialData == nil {
 				require.True(t, os.IsNotExist(err))
 			} else {
 				require.NoError(t, err)
-				modTimeBeforeCopy = stat.ModTime()
+				modTimeBefore = stat.ModTime()
 			}
 
-			err = CopyIfChanged(destFile, c.sourceData, 0o600)
+			err = WriteIfNeeded(destFile, c.sourceData, 0o600)
 			require.NoError(t, err)
 
-			statAfterCopy, err := os.Stat(destFile)
+			statAfter, err := os.Stat(destFile)
 			require.NoError(t, err)
+			modTimeAfter := statAfter.ModTime()
+
 			if c.expectWrite {
-				assert.Greater(t, statAfterCopy.ModTime().Truncate(time.Millisecond), modTimeBeforeCopy.Truncate(time.Millisecond))
+				assert.Greater(t, modTimeAfter.Truncate(time.Millisecond), modTimeBefore.Truncate(time.Millisecond))
 			} else {
-				assert.Equal(t, modTimeBeforeCopy.Truncate(time.Millisecond), statAfterCopy.ModTime().Truncate(time.Millisecond))
+				assert.Equal(t, modTimeBefore.Truncate(time.Millisecond), modTimeAfter.Truncate(time.Millisecond))
 			}
 
 			data, err := os.ReadFile(destFile)

internal/legacy/legacy.go

@@ -80,7 +80,7 @@ func (c *CLIWrapper) init() error {
 
 	g := errgroup.Group{}
 	g.Go(func() error {
-		if err := file.CopyIfChanged(c.pharPath(cacheDir), phar, 0o644); err != nil {
+		if err := file.WriteIfNeeded(c.pharPath(cacheDir), phar, 0o644); err != nil {
 			return fmt.Errorf("could not copy phar file: %w", err)
 		}
 		return nil
@@ -90,7 +90,7 @@ func (c *CLIWrapper) init() error {
 		if err != nil {
 			return fmt.Errorf("could not load config for checking: %w", err)
 		}
-		if err := file.CopyIfChanged(filepath.Join(cacheDir, configBasename), configContent, 0o644); err != nil {
+		if err := file.WriteIfNeeded(filepath.Join(cacheDir, configBasename), configContent, 0o644); err != nil {
 			return fmt.Errorf("could not write config: %w", err)
 		}
 		return nil

internal/legacy/php_unix.go

@@ -11,7 +11,7 @@ import (
 
 // copyPHP to destination, if it does not exist
 func (c *CLIWrapper) copyPHP(cacheDir string) error {
-	return file.CopyIfChanged(c.phpPath(cacheDir), phpCLI, 0o755)
+	return file.WriteIfNeeded(c.phpPath(cacheDir), phpCLI, 0o755)
 }
 
 // phpPath returns the path to the temporary PHP-CLI binary

internal/legacy/php_windows.go

@@ -42,7 +42,7 @@ func (c *CLIWrapper) copyPHP(cacheDir string) error {
 		return err
 	}
 
-	if err := file.CopyIfChanged(filepath.Join(destDir, "extras", "cacert.pem"), caCert, 0o644); err != nil {
+	if err := file.WriteIfNeeded(filepath.Join(destDir, "extras", "cacert.pem"), caCert, 0o644); err != nil {
 		return err
 	}