Lossless Document Merger

AppendDocument clones every section of src onto dst, then remaps identifiers that would collide inside one OpenXML package. The result is a single ZIP whose styles, bookmarks, and media do not overwrite each other.

AppendDocument

Signature

func (d *Document) AppendDocument(src *Document, opts MergeOptions) error

type MergeOptions struct {
	StylePrefix    string
	BookmarkPrefix string
	SectionBreak   string
}

Parameters

Name	Type	Description
src	*Document	Source tree. nil returns word: nil source document.
StylePrefix	string	Prefix for colliding paragraph/table style IDs. Default src_.
BookmarkPrefix	string	Prefix for colliding w:bookmarkStart names. Default src_.
SectionBreak	string	Break on the first cloned section. Default nextPage.

What gets remapped

Identifier	Behaviour
Paragraph / table style IDs	Colliding names receive the prefix (Note → src_Note)
Bookmark names	Colliding names are prefixed; unique names stay
Internal hyperlink anchors	Updated to the new bookmark names
Images / media	RelationID cleared; writer assigns fresh rId and word/media/imageN

rIds are allocated at write time (word2007Writer.nextRel), so two documents never share a relationship ID in the merged ZIP.

Complete example

package main

import (
	"bytes"
	"image"
	"image/color"
	"image/png"
	"log"

	"github.com/yunkeweb/go-word"
	"github.com/yunkeweb/go-word/style"
)

func main() {
	dst := word.New()
	dst.AddParagraphStyle("Note", style.Paragraph{Spacing: style.Spacing{After: 120}})
	a := dst.AddSection()
	a.AddTitle("Document A", 1)
	a.AddText("Bookmark and image from A.", nil, "Note")
	a.AddBookmark("shared")
	a.AddImageBytes("a.png", swatch(color.RGBA{R: 31, G: 78, B: 121, A: 255}), style.Image{Width: 40, Height: 20})

	src := word.New()
	src.AddParagraphStyle("Note", style.Paragraph{Spacing: style.Spacing{After: 200}})
	b := src.AddSection()
	b.AddTitle("Document B", 1)
	b.AddText("Bookmark, image and formula from B.", nil, "Note")
	b.AddBookmark("shared")
	b.AddImageBytes("b.png", swatch(color.RGBA{R: 237, G: 125, B: 49, A: 255}), style.Image{Width: 40, Height: 20})
	b.AddMath(`\frac{1}{2}`)

	if err := dst.AppendDocument(src, word.MergeOptions{SectionBreak: "nextPage"}); err != nil {
		log.Fatal(err)
	}
	if err := dst.Save("merged.docx"); err != nil {
		log.Fatal(err)
	}
}

func swatch(c color.RGBA) []byte {
	img := image.NewRGBA(image.Rect(0, 0, 40, 20))
	for y := 0; y < 20; y++ {
		for x := 0; x < 40; x++ {
			img.Set(x, y, c)
		}
	}
	var buf bytes.Buffer
	if err := png.Encode(&buf, img); err != nil {
		log.Fatal(err)
	}
	return buf.Bytes()
}

What Word shows

Two pages. Page 1 is navy-blue swatch + Document A. Page 2 starts after a next-page section break, shows the orange swatch, and contains an editable 1/2 fraction. Styles.xml contains both Note and src_Note (different after-spacing). Bookmarks shared and src_shared both exist. The ZIP has word/media/image1.png and image2.png with distinct rIds — unzipping never overwrites a picture.