Creating removable comment command without extra space

Question

I'm trying to create a command we can use for comments in our document. During development, we want the comments to appear; for production, we want them to disappear. This is a common enough problem with many solutions.

I'm having an issue with LaTeX's tokenizer, though; if the command is surrounded by spaces, two spaces are emitted. I understand why that's happening, but none of the workarounds that I can find are any good for me. Here's a representative example.

\documentclass[letterpaper]{article}

\newif\ifnotes
\newcommand{\note}[1]{\ifnotes{#1}\fi}
\notesfalse
\newcommand{\nonotes}{\notesfalse}

\begin{document}
\pagestyle{empty}

Testing \note{X} testing testing.

\end{document}

Because \notesfalse has been invoked, the note should not (and does not) appear. But the spaces to the left and right of the command do appear, which is a problem for me.

I could modify the command to eat all of the spaces after it, but this isn't really the correct behavior either; if the command only has spaces following (as in the\note{...} text), there should still be an emitted space. While I know that one can use things like \unskip to delete preceding space, I'm at a loss to detect the preceding (and following) space so I can make an intelligent decision about whether it should stick around.

Does anyone have any suggestions for accomplishing this task?

Answer 1

Here is a solution

\documentclass[letterpaper]{article}

\newif\ifnotes
\makeatletter
\newcommand{\note}[1]{\@bsphack\ifnotes{#1}\fi\@esphack}
\makeatother
\notesfalse
\newcommand{\nonotes}{\notesfalse}

\begin{document}
\pagestyle{empty}

Testing \note{X} testing testing.

Testing\note{X} testing testing.

Testing \note{X}testing testing.

Testing\note{X}testing testing.

\notestrue

Testing \note{X} testing testing.

Testing\note{X} testing testing.

Testing \note{X}testing testing.

Testing\note{X}testing testing.

\end{document}