As there seems to be some confusion when hard tab characters (ASCII code 9) are appropriate in source code files here is a rule:
1) Never use hard tabs
1. 1) Unless your source code is hard tab sensitive (only such format I know is Makefile)
Reasons not to use hard tabs
- Due to legacy, different text editors treat hard tabs different. UNIX text editors prefer hard tab is 8 spaces, Windows text editors and IDEs (Eclipse) prefer that a hard tab is 4 spaces.
- The hard tab length agreement between different text editors cannot be reached
- The hard tab length agreement between people cannot be reached
- Thus, hard tabs may break source code readability and editability if there is more than a single person editing the file. They will open the file in an editor with different tab settings, edit it and next time you open the file it is ruined and all indentations are wrong.
- This is even worse on white space sensitive languages (Python, CoffeeScript) as this might actually cause syntax errors or programming logic errors
However, you can avoid this problem in the first place if you do indentation using soft tabs (spaces) instead.
Even if you were the single person in the world editing the text file, even you might switch the text editor in some point and accidentally shoot yourself in the leg.
Using soft tabs for indentation and having no hard tabs should not be a problem because
- All text editors can convert tabs to spaces in fly, when editing the file. Please note me if there are commonly used editors, besides Windows Notepad, which doesn’t do it yet.
- Text editors usually have different settings to tab key length and indentation settings. The latter is what you really want to adjust.
Pseudo-arguments for using hard tabs
- It makes the file size smaller: you really care about those twenty bytes on our terabyte hard disks?
- This one I made up: spaces count toward the file size in web stuff, because visitors download the files. However if those bytes really matter you that much you should be using a minimizer in the first place.
- I like them arguments…: rationale not involved
- The change resistance in human nature
You might have a legacy software project having its legacy style guides. If the project big, e.g. Linux kernel, the switching cost may be very high and not affordable. However, even with this kind of codebase, you can gradually replace hard tabs away.
Style guides
- Python style guide recommends no hard tabs
- PHP style guide recommends no hard tabs
- Java style guide recommends no hard tabs
- CSS style guide recommends no hard tabs
- etc.
Text editors
If you are a text editor author, make sure your text editor ships with hard tabs turned off by default, especially for whitespace sensitive languages if you vary tab policy by file type.
Note that this blog post, and the situation, could have been avoided if
- All text editors would have sticked to soft tabs by default
- All text editors would have sticked to a hard tab is 8 spaces by default
But in some point (when?) someone (who?) decided to make our life little more complex.
