texdiff

AST-driven semantic diff for LaTeX documents.

texdiff compares two revisions of a LaTeX document and produces a single marked-up diff.tex that compiles with pdflatex — added text in blue, deleted text struck out — while preserving the original document's styling, cross-references and custom classes.

Why

latexdiff is the de-facto standard for review-marked LaTeX, but it diffs token soup: it guesses word boundaries with regexes and re-injects markup into the merged text, hoping braces still balance. On real-world documents the result is markup that crosses brace / environment boundaries, glues old and new table cells together, and corrupts listings — which is why every serious latexdiff user eventually ends up maintaining a pile of fragile pre/post-processing scripts around it.

texdiff takes the other road: diff the tree, never the text.

1. Parse old and new documents into a LaTeX syntax tree (pylatexenc — a faithful concrete syntax tree carrying exact source spans, no macro expansion).
2. Align the trees level by level (document → environments → groups → text runs) with difflib-style sequence matching. A change can never leak across a node boundary.
3. Walk the merged tree and emit \DIFadd{...} / \DIFdel{...} markup — latexdiff-compatible rendering, valid by construction.

Restructured tables (re-ordered rows, changed column layouts), math, listings and verbatim environments are handled as atomic or row-aligned blocks instead of being shredded by a word diff.

Multi-file sources are flattened automatically (\input/\include resolved relative to each file, like latexdiff --flatten), and the preamble of the new revision is used verbatim so custom classes and macros keep working.

Usage

texdiff old/main.tex new/main.tex > diff.tex   # \input expansion built in
pdflatex diff.tex                              # done - no pre/postprocessing
texdiff old.tex new.tex -o diff.tex --check    # + fail loudly if it won't compile
texdiff old.tex new.tex --stats                # "611 unchanged, 29 added, ..."

pip install texdiff        # or from a checkout:
pip install -e ".[dev]" && pytest

Status: v0.2.0 — core pipeline plus flattening, row-granular table alignment, preamble policy, --check and a compile-guaranteed corpus in CI; validated on a 65-page generated longtable-heavy document. See the roadmap for what is next.

License

MIT