fix nil pointer for xlsx sharedStrings; add log

VERSION

@@ -1 +1 @@
-1.0.2
+1.0.3

docxtotext/docxtotext.go

@@ -228,6 +228,7 @@ func (dp *DocxParser) ExtractTexts() (string, error) {
 //   - error: an error if any.
 func (dp *DocxParser) extractDocument() (*strings.Builder, error) {
 	if dp.documentFile == nil {
+		dp.logWarn(types.ErrNoDocument)
 		return new(strings.Builder), nil
 	}
 
@@ -342,6 +343,11 @@ NEXT:
 //   - *strings.Builder: a strings.Builder containing the extracted comments text.
 //   - error: an error if any.
 func (dp *DocxParser) extractComments() (*strings.Builder, error) {
+	if dp.commentsFile == nil {
+		dp.logWarn(types.ErrNoComments)
+		return new(strings.Builder), nil
+	}
+
 	rc, err := dp.commentsFile.Open()
 	if err != nil {
 		return nil, err
@@ -388,6 +394,11 @@ NEXT:
 //   - *strings.Builder: a strings.Builder containing the extracted endnotes text.
 //   - error: an error if any.
 func (dp *DocxParser) extractEndnotes() (*strings.Builder, error) {
+	if dp.endnotesFile == nil {
+		dp.logWarn(types.ErrNoEndnotes)
+		return new(strings.Builder), nil
+	}
+
 	rc, err := dp.endnotesFile.Open()
 	if err != nil {
 		return nil, err
@@ -441,6 +452,11 @@ NEXT:
 //   - *strings.Builder: a strings.Builder containing the extracted footnotes text.
 //   - error: an error if any.
 func (dp *DocxParser) extractFootnotes() (*strings.Builder, error) {
+	if dp.footnotesFile == nil {
+		dp.logWarn(types.ErrNoFootnotes)
+		return new(strings.Builder), nil
+	}
+
 	rc, err := dp.footnotesFile.Open()
 	if err != nil {
 		return nil, err

types/errors.go

@@ -8,9 +8,14 @@ package types
 import "errors"
 
 var (
-	ErrNilZipFile = errors.New("the input zip file is nil")
-	ErrEmptyRID   = errors.New("the rId is empty")
-	ErrNonePart   = errors.New("the document part resolves failed or not exists")
-	ErrNoSlide    = errors.New("the specified slide is not found")
-	ErrNoSheet    = errors.New("the specified sheet is not found")
+	ErrNilZipFile      = errors.New("the input zip file is nil")
+	ErrEmptyRID        = errors.New("the rId is empty")
+	ErrNonePart        = errors.New("the document part resolves failed or not exists")
+	ErrNoSlide         = errors.New("the specified slide is not found")
+	ErrNoSheet         = errors.New("the specified sheet is not found")
+	ErrNoSharedStrings = errors.New("the sharedStrings.xml file is not found")
+	ErrNoDocument      = errors.New("the document.xml file is not found")
+	ErrNoComments      = errors.New("the comments.xml file is not found")
+	ErrNoEndnotes      = errors.New("the endnotes.xml file is not found")
+	ErrNoFootnotes     = errors.New("the footnotes.xml file is not found")
 )

xlsxtotext/xlsxtotext.go

@@ -217,6 +217,11 @@ func (xp *XlsxParser) ExtractTexts() (string, error) {
 //   - error: An error if there is any issue with opening the file or parsing
 //     the XML elements.
 func (xp *XlsxParser) parseSharedStrings() error {
+	if xp.sharedStringsFile == nil {
+		xp.logWarn(types.ErrNoSharedStrings)
+		return nil
+	}
+
 	rc, err := xp.sharedStringsFile.Open()
 	if err != nil {
 		return err