# aclements / latexrun

A 21st century LaTeX wrapper

## Latest commit

Austin Clements committed Nov 18, 2015
This commit adds database locking for UNIX-like systems.

Fixes #33.

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See LaTeX run. Run latexrun.

latexrun fits LaTeX into a modern build environment. It hides LaTeX's circular dependencies, surfaces errors in a standard and user-friendly format, and generally enables other tools to do what they do best.

# Features

• Runs latex the right number of times. LaTeX's iterative approach is a poor match for build tools that expect to run a task once and be done with it. latexrun hides this complexity by running LaTeX (and BibTeX) as many times as necessary and no more. Only the results from the final run are shown, making it act like a standard, single-run build task.

• Surfaces error messages and warnings. LaTeX and related tools bury errors and useful warnings in vast wastelands of output noise. latexrun prints only the messages that matter, in a format understood by modern tools. latexrun even figures out file names and line numbers for many BibTeX errors that usually don't indicate their source.

  paper.tex:140: Overfull \hbox (15pt too wide)
paper.tex:400: Reference sec:eval' on page 5 undefined
local.bib:230: empty booktitle in clements:commutativity

• Incremental progress reporting. latexrun keeps you informed of LaTeX's progress, without overwhelming you with output.

• Cleaning. LaTeX's output files are legion. latexrun keeps track of them and can clean them up for you.

• Atomic commit. latexrun updates output files atomically, which means your PDF reader will no longer crash or complain about broken xref tables when it catches latex in the middle of writing out a PDF.

• Easy {.git,.hg,svn:}ignore. Just ignore latex.out/. Done!

• Self-contained. latexrun is a single, self-contained Python script that can be copied in to your source tree so your collaborators don't have to install it.

## Non-features

Kitchen sink not included. latexrun is not a build system. It will not convert your graphics behind your back. It will not continuously monitor your files for changes. It will not start your previewer for you. latexrun is designed to be part of your build system and let other tools do what they do well.

# Integrating with make

latexrun does its own dependency tracking (at a finer granularity than make). Since it also does nothing if no dependencies have changed, it's easy to integrate with make using phony targets. Here's a complete example:

.PHONY: FORCE
paper.pdf: FORCE {files that need to be generated, if any}
latexrun paper.tex

.PHONY: clean
clean:
latexrun --clean-all

Note that paper.pdf depends on a phony target, but is not itself phony, since this would cause make to consider anything that depended on paper.pdf to always be out of date. Instead, make only considers targets that depend on paper.pdf out of date if latexrun actually updates paper.pdf.

# Comparison with other tools

Several other tools achieve the same basic goal as latexrun: to automatically run LaTeX and BibTeX the right number of times.

## Rubber

Rubber inspired many features of latexrun. Rubber showed that it's possible to abstract away many of LaTeX's eccentricities like iterative builds and user-hostile logs. latexrun is a response to Rubber: it attempts to capture its best features while further modernizing the LaTeX build process and adhering to the Unix philosophy of "do one thing well."

latexrun has more user-friendly and modern defaults than Rubber. It defaults to reporting important warnings like unknown references, rather than suppressing all warnings. It defaults to PDF output, rather than DVI output. It defaults to putting all intermediate output in a directory, rather than inheriting LaTeX's default behavior of filling your source tree with intermediate files. It also has features that interact better with modern tools, like atomic commit for PDF viewers that use file system notification to automatically refresh.

latexrun has robust post-execution dependency analysis, while Rubber works by parsing your TeX code. TeX is, famously, the only thing that can correctly parse TeX code and as a result Rubber's dependency analysis is fragile. Simple things like

    \newcommand{\includegraph}[1]{\includegraphics{graph/#1.pdf}}
\includegraph{results}

break Rubber's dependency analysis.

latexrun is simple. It's intentionally a single, self-contained, and reasonably short Python script that you can drop in next to your LaTeX sources so your collaborators don't have to install it. Rubber is modular, which is admirable but results in a non-zero setup cost.

latexrun fits in to your toolchain, while Rubber tries to replace it. Rubber goes beyond building LaTeX code with "features" like automatic graphics conversion based on a weighted shortest-path walk through known converters. This makes its build process unpredictable and means that other build tools like make integrate poorly with it. latexrun prefers explicit over implicit, and tries to make latex act like a modern tool in your toolchain to enable other tools to do what they do best.

## latexmk

latexmk is a venerable LaTeX wrapper that has amassed an impressive array of options, flags, and features. It includes many features that latexrun leaves to other tools---like starting viewers, printing, and conversion to PDF from DVI and PostScript---or simply omits---like adding banners and automatically invoking make for missing files.

Like latexrun, latexmk can use the "file recorder" feature of modern TeX engines to compute precise file dependencies. However, latexrun also tracks non-file dependencies like environment variables and knows how to track filtered file contents (like only the lines that actually matter to BibTeX).

latexmk simply passes through LaTeX's log spew, while latexrun extracts errors and warnings and displays them in a friendly, modern format.

# How latexrun works

latexrun views the world as a cyclic graph of deterministic functions of system state:

     .tex → ┌───────┐ ─────────────────────────→ .pdf
╭─── .aux → │       │ → .aux ──╮
│╭── .toc → │ latex │ → .toc ─╮│
││╭─ .bbl → │       │ → .log  ││
│││     … → └───────┘ → …     ││
│╰────────────────────────────╯│
╰──────────────────────────────┤
│                            ↓
│                 .bst → ┌────────┐ → .blg
│                 .bib → │ bibtex │ → .bbl ─╮
│                        └────────┘         │
╰───────────────────────────────────────────╯


latexrun's goal is to find the fixed-point of this computation. Put simply, it runs latex and bibtex repeatedly until it can guarantee that additional runs will not change the output.

A direct approach could be to check the output of latex and bibtex after each run and stop when the output is the same from one run to the next. This works, but runs latex too many times; it will have already produced its final output one iteration before this approach can figure out that it's done.

Instead, latexrun models latex and bibtex as deterministic functions of the file system state, their command-line arguments, and certain environment variables. Hence, if the inputs to latex and bibtex do not change over one iteration, then latexrun can guarantee that the output also will not change, and stop.

# Known issues

When a missing file is silently ignored by latex (e.g., \openin, \IfFileExists), latexrun can't track that the lack of that file was important. Hence, if a missing file is later created, latexrun may not re-run latex. However, missing files that cause latex to abort (e.g., missing files in \input) as well as missing \include files (which do not cause aborts) are handled.

Command-line usage errors when calling latex appear before "This is pdfTeX" and are not logged and therefore often not reported.

# To do

• Solve the problem of missing input files. LaTeX doesn't record inputs that it couldn't read, so we don't know about them even though they affect the computation (often seriously!). Possible solutions include ptrace, FUSE, and fanotify, but none of these are portable or easily accessible from Python.

• Provide a way to disable output filters for things that do their own output parsing (e.g., AUCTeX).

• Integrate even better with make. Phony rules are okay, but will force make dependencies to be generated even if latexrun ultimately does nothing. Since latexrun's dependencies are finer-grained than make`'s, it might be necessary to shell out to latexrun to do this.

• Separate clean data by source file so you can clean a single input file's outputs.

• Some important things like undefined references are only considered warnings since they don't stop compilation. Maybe distinguish document-mangling warnings (almost but not quite errors) and format warnings (can be ignored if justified).

• Perhaps separate out the LaTeX output filter so it can be used on its own as a pipe filter. It could even be used on high-level output, like from make, by acting as a pass-through until the "This is (pdf)TeX" line up to the "Transcript written on" line (or anything else that can end TeX's log output).

A 21st century LaTeX wrapper