Fixes #156 - Update os backend to use new io integration test suite

backend/os/file.go

@@ -3,6 +3,7 @@ package os
 import (
 	"fmt"
 	"io"
+	"io/fs"
 	"os"
 	"path"
 	"path/filepath"
@@ -27,6 +28,8 @@ type File struct {
 	tempFile    *os.File
 	useTempFile bool
 	fileOpener  opener
+	seekCalled  bool
+	readCalled  bool
 }
 
 // Delete unlinks the file returning any error or nil.
@@ -73,6 +76,8 @@ func (f *File) Size() (uint64, error) {
 func (f *File) Close() error {
 	f.useTempFile = false
 	f.cursorPos = 0
+	f.seekCalled = false
+	f.readCalled = false
 
 	// check if temp file
 	if f.tempFile != nil {
@@ -128,6 +133,7 @@ func (f *File) Read(p []byte) (int, error) {
 		return read, err
 	}
 
+	f.readCalled = true
 	f.cursorPos += int64(read)
 
 	return read, nil
@@ -137,6 +143,13 @@ func (f *File) Read(p []byte) (int, error) {
 // the file, 1 means relative to the current offset, and 2 means relative to the end.  It returns the new offset and
 // an error, if any.
 func (f *File) Seek(offset int64, whence int) (int64, error) {
+	exists, err := f.Exists()
+	if err != nil {
+		return 0, fmt.Errorf("unable to Seek: %w", err)
+	}
+	if !exists && !f.useTempFile {
+		return 0, fmt.Errorf("unable to Seek: %w", fs.ErrNotExist)
+	}
 	useFile, err := f.getInternalFile()
 	if err != nil {
 		return 0, err
@@ -147,6 +160,7 @@ func (f *File) Seek(offset int64, whence int) (int64, error) {
 		return 0, err
 	}
 
+	f.seekCalled = true
 	return f.cursorPos, err
 }
 
@@ -167,6 +181,7 @@ func (f *File) Exists() (bool, error) {
 
 // Write implements the io.Writer interface.  It accepts a slice of bytes and returns the number of bytes written and an error, if any.
 func (f *File) Write(p []byte) (n int, err error) {
+	// useTempFile prevents the immediate update of the file until we Close()
 	f.useTempFile = true
 
 	useFile, err := f.getInternalFile()
@@ -428,23 +443,33 @@ func (f *File) copyToLocalTempReader() (*os.File, error) {
 		return nil, err
 	}
 
-	openFunc := openOSFile
-	if f.fileOpener != nil {
-		openFunc = f.fileOpener
+	exists, err := f.Exists()
+	if err != nil {
+		return nil, err
 	}
+	if exists {
+		openFunc := openOSFile
+		if f.fileOpener != nil {
+			openFunc = f.fileOpener
+		}
 
-	if _, err = openFunc(f.Path()); err != nil {
-		return nil, err
+		actualFile, err := openFunc(f.Path())
+		if err != nil {
+			return nil, err
+		}
+		if f.seekCalled || f.readCalled {
+			if _, err := io.Copy(tmpFile, actualFile); err != nil {
+				return nil, err
+			}
+		}
+
+		if f.cursorPos > 0 {
+			// match cursor position in tmep file
+			if _, err := tmpFile.Seek(f.cursorPos, 0); err != nil {
+				return nil, err
+			}
+		}
 	}
-	// todo: editing in place logic/appending logic (see issue #42)
-	// if _, err := io.Copy(tmpFile, f.file); err != nil {
-	//	return nil, err
-	// }
-	//
-	// // Return cursor to the beginning of the new temp file
-	// if _, err := tmpFile.Seek(f.cursorPos, 0); err != nil {
-	//	return nil, err
-	// }
 
 	return tmpFile, nil
 }

backend/os/file_test.go

@@ -506,6 +506,7 @@ func (s *osFileTest) TestWrite() {
 	// setup file for err out of opening
 	f, err := s.tmploc.NewFile("test_files/writeFileFail.txt")
 	s.NoError(err)
+	s.NoError(f.Touch())
 	f.(*File).useTempFile = true
 	f.(*File).fileOpener = func(filePath string) (*os.File, error) { return nil, errors.New("bad opener") }
 	data = make([]byte, 4)
@@ -538,29 +539,30 @@ func (s *osFileTest) TestCursor() {
 	s.Equal(int64(5), file.(*File).cursorPos)
 	s.NoError(serr2)
 
+	// because seek and/or read were called before write, write is now in in-place edit mode (not truncate-write)
 	sz, werr = file.Write([]byte("has")) // cursor 8 - tempfile copy of orig - write on tempfile has occurred
 	s.NoError(werr)
 	s.Equal(int64(8), file.(*File).cursorPos)
 	s.Equal(3, sz)
 
-	_, serr = file.Seek(0, 0) // cursor 0 - in temp file
-	s.Equal(int64(0), file.(*File).cursorPos)
+	_, serr = file.Seek(5, 0) // cursor 0 - in temp file
+	s.Equal(int64(5), file.(*File).cursorPos)
 	s.NoError(serr)
 
 	data = make([]byte, 3)
 	sz, rerr = file.Read(data)
 	s.NoError(rerr)
-	s.Equal(int64(3), file.(*File).cursorPos)
+	s.Equal(int64(8), file.(*File).cursorPos)
 	s.Equal("has", string(data)) // tempFile contents = "has"
 	s.Equal(3, sz)
 
 	s.NoError(file.Close()) // moves tempfile containing "has" over original file
 
-	final := make([]byte, 3)
+	final := make([]byte, 8)
 	rd, err := file.Read(final)
 	s.NoError(err)
-	s.Equal(3, rd)
-	s.Equal("has", string(final))
+	s.Equal(8, rd)
+	s.Equal("mary has", string(final))
 	s.NoError(file.Close())
 
 	// if a file exists and we overwrite with a smaller # of text, then it isn't completely overwritten

backend/os/location_test.go

@@ -158,6 +158,8 @@ func (s *osLocationTest) TestDeleteFile() {
 	_, err = file.Write([]byte(expectedText))
 	s.NoError(err, "Shouldn't fail to write text to file.")
 
+	s.NoError(file.Close())
+
 	exists, err := file.Exists()
 	s.NoError(err, "Exists shouldn't throw error.")
 	s.True(exists, "Exists should return true for test file.")