From 0b59a4f28483d40d227a92b439274bc55ebc8f2f Mon Sep 17 00:00:00 2001
From: John Judd <john.judd@c2fo.com>
Date: Mon, 22 Jan 2024 13:14:46 -0600
Subject: [PATCH] Fixed #152 bug where s3 backend failed to read empty files
 (#153)

* Fixed #152 bug where s3 backend failed to read empty files

* corrected changelog version
---
 CHANGELOG.md            |  4 ++++
 backend/s3/file.go      | 40 +++++++++++++++++++++++++---------------
 backend/s3/file_test.go | 16 ++++++++++++++++
 3 files changed, 45 insertions(+), 15 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b9cb6a08..bbe20ea0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 ## [Unreleased]
 
+## [6.11.1] - 2024-01-22
+### Fixed
+- Fixed #152 bug where s3 backend failed to read empty files
+
 ## [6.11.0] - 2024-01-22
 ### Added
 - Added support for hmac-sha1 and hmac-sha1-96 and removed hmac-ripemd160 
diff --git a/backend/s3/file.go b/backend/s3/file.go
index 26308706..fa377d9a 100644
--- a/backend/s3/file.go
+++ b/backend/s3/file.go
@@ -7,6 +7,7 @@ import (
 	"io"
 	"net/url"
 	"path"
+	"strings"
 	"time"
 
 	"github.com/aws/aws-sdk-go/aws/awserr"
@@ -535,26 +536,35 @@ func waitUntilFileExists(file vfs.File, retries int) error {
 
 func (f *File) getReader() (io.ReadCloser, error) {
 	if f.reader == nil {
-		// Create the request to get the object
-		input := new(s3.GetObjectInput).
-			SetBucket(f.bucket).
-			SetKey(f.key).
-			SetRange(fmt.Sprintf("bytes=%d-", f.cursorPos))
-
-		// Get the client
-		client, err := f.fileSystem.Client()
+		sz, err := f.Size()
 		if err != nil {
 			return nil, err
 		}
+		if sz == 0 {
+			f.reader = io.NopCloser(strings.NewReader(""))
+		} else {
 
-		// Request the object
-		result, err := client.GetObject(input)
-		if err != nil {
-			return nil, err
-		}
+			// Create the request to get the object
+			input := new(s3.GetObjectInput).
+				SetBucket(f.bucket).
+				SetKey(f.key).
+				SetRange(fmt.Sprintf("bytes=%d-", f.cursorPos))
 
-		// Set the reader to the body of the object
-		f.reader = result.Body
+			// Get the client
+			client, err := f.fileSystem.Client()
+			if err != nil {
+				return nil, err
+			}
+
+			// Request the object
+			result, err := client.GetObject(input)
+			if err != nil {
+				return nil, err
+			}
+
+			// Set the reader to the body of the object
+			f.reader = result.Body
+		}
 	}
 	return f.reader, nil
 }
diff --git a/backend/s3/file_test.go b/backend/s3/file_test.go
index 914c7ddd..b491f9ec 100644
--- a/backend/s3/file_test.go
+++ b/backend/s3/file_test.go
@@ -63,6 +63,10 @@ func (ts *fileTestSuite) TestRead() {
 	}
 
 	var localFile = bytes.NewBuffer([]byte{})
+	s3apiMock.
+		On("HeadObject", mock.AnythingOfType("*s3.HeadObjectInput")).
+		Return(&s3.HeadObjectOutput{ContentLength: aws.Int64(12)}, nil).
+		Once()
 	s3apiMock.
 		On("GetObject", mock.AnythingOfType("*s3.GetObjectInput")).
 		Return(&s3.GetObjectOutput{Body: io.NopCloser(strings.NewReader(contents))}, nil).
@@ -74,6 +78,10 @@ func (ts *fileTestSuite) TestRead() {
 	ts.Equal(contents, localFile.String(), "Copying an s3 file to a buffer should fill buffer with file's contents")
 
 	// test read with error
+	s3apiMock.
+		On("HeadObject", mock.AnythingOfType("*s3.HeadObjectInput")).
+		Return(&s3.HeadObjectOutput{ContentLength: aws.Int64(12)}, nil).
+		Once()
 	s3apiMock.
 		On("GetObject", mock.AnythingOfType("*s3.GetObjectInput")).
 		Return(nil, errors.New("some error")).
@@ -135,6 +143,10 @@ func (ts *fileTestSuite) TestSeek() {
 			ts.Equal(tc.expectedPos, pos, "Expected position does not match for seek offset %d and whence %d", tc.seekOffset, tc.seekWhence)
 
 			// Mock the GetObject call
+			s3apiMock.
+				On("HeadObject", mock.AnythingOfType("*s3.HeadObjectInput")).
+				Return(headOutput, nil).
+				Once()
 			s3apiMock.On("GetObject", mock.AnythingOfType("*s3.GetObjectInput")).
 				Return(&s3.GetObjectOutput{Body: io.NopCloser(strings.NewReader(tc.readContent))}, nil).
 				Once()
@@ -235,6 +247,10 @@ func (ts *fileTestSuite) TestEmptyCopyToFile() {
 	targetFile := &mocks.File{}
 	targetFile.On("Write", mock.Anything).Return(0, nil)
 	targetFile.On("Close").Return(nil)
+	s3apiMock.
+		On("HeadObject", mock.AnythingOfType("*s3.HeadObjectInput")).
+		Return(&s3.HeadObjectOutput{ContentLength: aws.Int64(0)}, nil).
+		Once()
 	s3apiMock.
 		On("GetObject", mock.AnythingOfType("*s3.GetObjectInput")).
 		Return(&s3.GetObjectOutput{Body: io.NopCloser(strings.NewReader(""))}, nil).