Why doesn't latexmk handle errors in the preamble?

Question

Today I discovered that if I have an error in the preamble of my tex file then Latexmk produce an error only once.

Precisely, for example if my file looks like this

\documentclass{article}
\someWrongCommand{foo}
\begin{document}
bar
\end{document}

then of course both latexmk and pdflatex produce an error in the line \someWrongCommand{foo}. But if I then compile the file with latexmk for the second time (without changing anything in my file) then letexmk just says

Latexmk: All targets (file.pdf) are up-to-date

Whats more, if I have an error in the document (not in the preamble) then latexmk shows an error all the time (not only in the first compile) as I wish.

Is it possible to make latexmk behaves like pdflatex if there is an error in a preamble? I know I can use latexmk with -g option but it is not a solution because then it always recompile everything from scratch.

I just want latexmk to handles errors in the preamble no matter in which compilation.

Answer 1

From latexmk's point of view, errors in the preamble are treated no differently than those in the body. If you are getting a difference, it is because you or pdflatex are reacting differently to the error.

The behavior of latexmk follows from that of pdflatex and is as follows:

• If pdflatex finds an error and you tell it to exit, then no pdf file is created. Any already existing pdf file will be unchanged.
• If you respond to error by telling pdflatex to continue, then a new pdf file will (normally) be produced. (But latexmk will see that there is an error, and not do postprocessing, e.g., forcing a previewer update.)

On a subsequent run, if the pdf file exists and if the source files are unchanged, then latexmk will not rerun pdflatex. This is normally correct behavior, since (normally) rerunning pdflatex won't change the error condition until a source file is changed. If there is no pdf file, a subsequent run of latexmk will notice the non-existence of the pdf file and therefore (pointlessly) rerun pdflatex and reproduce the error. (Perhaps I need latexmk to cache the existence of an error condition, and save the extra run.)

I definitely don't want to change latexmk to remove the pdf file if pdflatex reports an error, since generally the principle of latexmk is that it should respect the behavior of the programs it calls.