Insert spaces instead of TABs


If you want an easier life, make sure that all your editors insert spaces instead of TABs.


Every single project I've worked on since 2003, there has been an issue with someone on the project either not knowing the difference between TABs and spaces or not taking heed that all his or her editing environments are set properly up to deal with this. A lot of developers doesn't even know there is a difference. All they know, is that it looks nice "on their computer". The result is commits with too many lines changed and source code looking like a wreck because of inconsistent indentation.

The problem

If there's not a clear strategy of how to (or not use) TABs and characters, you end up with source code which look different in differnt editors, or when viewing them on the command line, when browsing the source code in the web browser or when using a code diffing utility. Inconsistent TAB/space usage also leads to code commits affecting far more lines of code than what actually was the real change intended by the developer.

When a file has inconsistent indentation, it looks messy (in Java projects, this is often the XML files). When a file looks messy, people stop caring about it. It becomes a broken window and the code starts to rot.

There are also cases where TABs will break things, like YAML files which requires indentation to be spaces only.

Set up ALL your editors to insert spaces instead of TABs


Be sure to include this in your ~/.emacs:

(setq-default indent-tabs-mode nil)


Be sure to include this in your ~/.vimrc:

set softtabstop=2
set expandtab


Settings → Preferences → Tab Settings → Replace by space (checkbox)

IntelliJ IDEA

Be sure this checkbox is not selected:

intellij idea no TABs


Be sure this checkbox is selected:

Eclipse no TABs

Replacing all TABs with spaces in a file

You can either copy a TAB character in your file and use the "Search and replace" feature in your editor to replace them with spaces. Alternatively, and is a better option if you want to unTABify many files, you can usesed. The following examples conerts TABs with two spaces and should work on both Unix, Linux and Windows/Cawing systems:

$ sed 's/\t/  /g' -i myfile.txt

To do this on a number of files (Java files in the below example), you should be able to do:

$ find . -name "*.java" | while read f; do (sed -i 's/\t/  /g' "$f"); done

Becoming more aware of whitespace


You can easily turn on and off the display of whitespace with:

M-x whitespace-mode

IntelliJ IDEA

IDEA has this in its General > Appearance settings:

intellij idea

No rule without exception

There's one notable exception here, where TABs not only is allowed, but even required and that's with Makefiles. If you edit a Makefile build file, you must use TABs.

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