Improve output of FileRetrievalError source errors

And update some names for consistency and spelling

epub.go

@@ -26,7 +26,6 @@ Basic usage:
 package epub
 
 import (
-	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -40,32 +39,24 @@ import (
 )
 
 // FilenameAlreadyUsedError is thrown by AddCSS, AddFont, AddImage, or AddSection
-// if the same filename is used more than once
+// if the same filename is used more than once.
 type FilenameAlreadyUsedError struct {
 	Filename string // Filename that caused the error
 }
 
 func (e *FilenameAlreadyUsedError) Error() string {
-	return "Filename already used: " + e.Filename
+	return fmt.Sprintf("Filename already used: %s", e.Filename)
 }
 
-// ErrInvalidSource is used inside FileRetrevalError for calls to
-// AddCSS, AddFont, AddImage, AddSection with an invalid file source.
-var ErrInvalidSource = errors.New("Invalid Source")
-
-// FileRetrevalError is thrown by Write in the case of a media file added with
-// AddImage, AddFont, AddCSS being unable to be read.
-type FileRetrevalError struct {
-	// File is the file that we failed to retreive.
-	File string
-
-	// Err is the underlying error that we encountered attempting to retreive File.
-	Err error
+// FileRetrievalError is thrown by AddCSS, AddFont, AddImage, or Write if there was a
+// problem retrieving the source file that was provided.
+type FileRetrievalError struct {
+	Source string // The source of the file whose retrieval failed
+	Err    error  // The underlying error that was thrown
 }
 
-// Error implements the error interface.
-func (e *FileRetrevalError) Error() string {
-	return fmt.Sprintf("Error retrieving %q from source: %+v", e.File, e.Err)
+func (e *FileRetrievalError) Error() string {
+	return fmt.Sprintf("Error retrieving %q from source: %+v", e.Source, e.Err)
 }
 
 // Folder names used for resources inside the EPUB
@@ -403,11 +394,11 @@ func (e *Epub) Title() string {
 // Add a media file to the EPUB and return the path relative to the EPUB section
 // files
 func addMedia(source string, internalFilename string, mediaFileFormat string, mediaFolderName string, mediaMap map[string]string) (string, error) {
-	// Make sure the source file is valid before proceeding
-	if isFileSourceValid(source) == false {
-		return "", &FileRetrevalError{
-			File: source,
-			Err:  ErrInvalidSource,
+	err := validateFileSource(source)
+	if err != nil {
+		return "", &FileRetrievalError{
+			Source: source,
+			Err:    err,
 		}
 	}
 
@@ -437,10 +428,10 @@ func addMedia(source string, internalFilename string, mediaFileFormat string, me
 	), nil
 }
 
-func isFileSourceValid(source string) bool {
+func validateFileSource(source string) error {
 	u, err := url.Parse(source)
 	if err != nil {
-		return false
+		return err
 	}
 
 	var r io.ReadCloser
@@ -449,7 +440,7 @@ func isFileSourceValid(source string) bool {
 	if u.Scheme == "http" || u.Scheme == "https" {
 		resp, err = http.Get(source)
 		if err != nil {
-			return false
+			return err
 		}
 		r = resp.Body
 
@@ -458,13 +449,13 @@ func isFileSourceValid(source string) bool {
 		r, err = os.Open(source)
 	}
 	if err != nil {
-		return false
+		return err
 	}
 	defer func() {
 		if err := r.Close(); err != nil {
 			panic(err)
 		}
 	}()
 
-	return true
+	return nil
 }

epub_test.go

@@ -567,12 +567,12 @@ func TestFilenameAlreadyUsedError(t *testing.T) {
 	}
 }
 
-func TestFileRetrevalError(t *testing.T) {
+func TestFileRetrievalError(t *testing.T) {
 	e := NewEpub(testEpubTitle)
 
 	_, err := e.AddCSS("/sbin/thisShouldFail", testCoverCSSFilename)
-	if _, ok := err.(*FileRetrevalError); !ok {
-		t.Errorf("Expected error FileRetrevalError not returned. Returned instead: %+v", err)
+	if _, ok := err.(*FileRetrievalError); !ok {
+		t.Errorf("Expected error FileRetrievalError not returned. Returned instead: %+v", err)
 	}
 }
 

write.go

@@ -19,7 +19,7 @@ type UnableToCreateEpubError struct {
 }
 
 func (e *UnableToCreateEpubError) Error() string {
-	return fmt.Sprintf("Error creating EPUB at path: %q, error: %+v", e.Path, e.Err)
+	return fmt.Sprintf("Error creating EPUB at %q: %+v", e.Path, e.Err)
 }
 
 var extensionMediaTypes = map[string]string{
@@ -318,7 +318,7 @@ func (e *Epub) writeMedia(tempDir string, mediaMap map[string]string, mediaFolde
 			// Get the media file from the source
 			u, err := url.Parse(mediaSource)
 			if err != nil {
-				return &FileRetrevalError{File: mediaSource, Err: err}
+				return &FileRetrievalError{Source: mediaSource, Err: err}
 			}
 
 			var r io.ReadCloser
@@ -327,7 +327,7 @@ func (e *Epub) writeMedia(tempDir string, mediaMap map[string]string, mediaFolde
 			if u.Scheme == "http" || u.Scheme == "https" {
 				resp, err = http.Get(mediaSource)
 				if err != nil {
-					return &FileRetrevalError{File: mediaSource, Err: err}
+					return &FileRetrievalError{Source: mediaSource, Err: err}
 				}
 				r = resp.Body
 
@@ -336,7 +336,7 @@ func (e *Epub) writeMedia(tempDir string, mediaMap map[string]string, mediaFolde
 				r, err = os.Open(mediaSource)
 			}
 			if err != nil {
-				return &FileRetrevalError{File: mediaSource, Err: err}
+				return &FileRetrievalError{Source: mediaSource, Err: err}
 			}
 
 			mediaFilePath := filepath.Join(
@@ -366,7 +366,7 @@ func (e *Epub) writeMedia(tempDir string, mediaMap map[string]string, mediaFolde
 			if err != nil {
 				// There shouldn't be any problem with the writer, but the reader
 				// might have an issue
-				return &FileRetrevalError{File: mediaSource, Err: err}
+				return &FileRetrievalError{Source: mediaSource, Err: err}
 			}
 
 			mediaType := extensionMediaTypes[strings.ToLower(filepath.Ext(mediaFilename))]