Updating Latex Packages Without Breaking Compatibility

The problem of package version incompatibility

LaTeX documents rely heavily on packages to extend core functionality. However, when package developers release updates, changes can sometimes break compatibility with existing documents. Some updates may introduce new bugs or remove previously available commands and features that documents depended on.

For example, an updated package may:

Rename internal commands used in documents
Change the syntax of package-specific macros and environments
Alter the output created by package functions
Drop support for previously valid input formats or use cases

Using an incompatible, updated package version can then cause LaTeX errors, changed output, missing content, or other unintended consequences. Fixing such issues across multiple affected documents can require substantial effort revising both package use and existing text.

Table of Contents

Understanding LaTeX package dependencies

Before updating any packages, determine which other packages and document class a project depends on. Core LaTeX only provides basic typesetting functionality. Most documents will at minimum also load:

A document class like \documentclass{article}, defining the document structure
Required packages enabling specific formatting, layouts, special content (macros, new environments) etc. Documents import these using \usepackage{}
Dependent packages loaded indirectly via required packages' \RequirePackage{} calls

For example, the amsmath mathematics package requires amstext. So documents loading amsmath also depend on amstext functionality. Updating either can potentially affect output.

Use LaTeX's log output to determine the full package dependency chainloaded for a project. Package updates must avoid altering depended-upon behavior other packages rely on.

Checking for compatibility issues

Using LaTeX compatibility checkers

Several LaTeX tools can automatically catch common package compatibility issues:

latexrevise compares LaTeX documents before and after package updates, checking for error changes and output differences.
latexdef verifies documents don't depend on deprecated, removed package commands scheduled for future dropping.
latexmp isolates incompatible packages causing issues after updates to the full dependency set.

First validate documents with these before deploying package updates live. The tools pinpoint problem commands, environments, and macros affected by changes requiring fixes.

Manually reviewing changes in new versions

Package developers post changes in uploaded versions to sites like CTAN. However, reliance purely on automated validators risks missing problems. Carefully review the modification list of any nontrivial package update, checking areas like:

Added, altered and removed commands/functionality
Bug fix details with potentially subtle side effects
Refactored internal code and structure
Updated dependee packages now also required

Search documents for uses of changed package components, and directly test any questionable cases. For example, a command taking different optional arguments may still work but produce different output hard for automated checks to identify.

Updating packages safely

Freezing package versions

When making significant document revisions, freeze all package versions by adding manual version number requirements. For example:

\usepackage[v1.3]{packageA}

This prevents automated tools from upgrading packages like packageA to newer releases potentially causing inadvertent issues. Finish document changes first before unfreezing dependencies and assessing new package versions.

Using package archives

When ready to update packages, utilize archives instead of directly using the latest version. For any nontrivial packagename update:

Locate and download the latest 1-2 archived, older releases (e.g. packagename v2.1 and packagename v2.2).
Test document compatibility with each archive incrementally before the bleeding edge.

This isolates compatibility-breaking changes, and allows smoothing any required fixes across multiple revision steps.

Forking packages locally

As a last resort when updates badly break a document:

Fork the last known good package version.
Apply custom fixes to restore lost functionality needed.
Use the fixed fork rather than the real package directly.

Manage such temporary custom versions carefully across documents and avoid publishing externally when possible.

Troubleshooting compatibility problems

Debugging error messages

LaTeX error logs pinpoint syntax issues with documents versus updated packages. Address messages like:

! Undefined control sequence.  
l.42 \someUnknownCommand

! Package somepackage Error: somepackage command now disabled.

This often occurs when a command name gets changed across versions. Search documents and replace old calls with the new syntax.

Isolating the source of issues

For less obvious LaTeX build failures after upgrades:

Bisect across packages and comment out \usepackage{} lines.
Determine which one triggers problems after isolation.
Scan its documentation for recent compatibility-breaking tweaks.
Refine root cause further by building with older archived releases.

Restore packages again once the problematic update gets identified and fixed.

Modifying documents or packages

When packages drop previously supported features, some degree of document modification becomes unavoidable. Possible avenues are:

Attempt to replace outdated usage with newer package conventions.
Support removed functionality with local workarounds.
Contribute changes improving backwards compatibility upstream to the external package.
As last resort, locally patch copies of packages used as described earlier.

Weigh the breaking change severity versus local fix complexity case-by-case.

Best practices for maintaining compatibility

Coordinating updates across documents

Follow version control best practices when updating document LaTeX distributions:

Maintain a central shared package set referenced across separate papers as submodules or similar.
revision this central dependency archive first with new package versions
Then propagate validated changes out across dependent writing projects.

This allows easier global fixes if issues emerge, with new package versions pre-validated before use by any manuscripts.

Communicating with collaborators

When handling coauthored LaTeX documents:

Openly communicate intentions and test procedure before directly updating shared packages.
Encourage reviewers to utilize latex validation tools locally if concerned.
Never rapidly update dependency sets shortly before submission releases or deadlines.

Follow best practices codified in internal typesetting guidelines. Scheduling coordination calls can preemptively align update plans across distributed groups.

Contributing fixes upstream

When updates genuinely break valid older functionality in standard packages external to a manuscript:

Isolate minimal reproducing usage examples demonstrating the issue.
Write the package developer politely highlighting the problems.
Contribute suggested improvements restoring backwards compatibility where feasible.

Often package authors remain responsive and welcome quality contributions improving LaTeX ecosystem stability from downstream users affected.