[natefinch]

Hugely disagree. Config files will modified by non-experts of the application 1000x as often as the actual developer of the application. Those people won't and often can't go look at the code.

Also, it can be really hard to find where exactly a configuration value is used. You may have to trace through a ton of code to find the place, and then you can't be sure that's the only place it's used.

Configuration comments are crucial, both for onboarding new users (explaining what the default is if you don't set a value, explaining what the configuration value actually controls, etc) and for experienced users to tell others why this esoteric configuration is set the way it is.

A configuration file is literally just a stack of magic numbers and strings. Why are we setting threadpool to 10 and not 1000? Why are we disabling X feature? What the heck does TPS_Report=true do?

You need comments.

[mlthoughts2018]

I disagree strongly. Config files being modified by anyone should be going through code review. The risk of not understanding while at the same time modifying things is extremely low.

Plus, the documentation in the application code that loads the config and manipulates would function as the exact same reference documentation for any developer trying to understand how the config is used or why a choice is made.

This prevents the documentation about what the config is supposed to be used for from being coupled with the implementation detail of what particular config file looks like, what language it’s written in, etc.

Just as you say, a config file is a stack of magic constants. They have no meaning at all sitting in that file. The place to look for their meaning is the documentation of the code that loads the file, which should tell the user everything they need to know about modifying or providing their own file.

[natefinch]

IF you have a 500k LOC software project... how the heck is an SRE/devops person going to figure out where in that code a specific configuration item is going to be used? They're not. This is why documentation is essential for projects. You could keep configuration documentation in a separate file... but that only helps for what the config does. It can't help you figure out why Bill (who left the company a while back) set ThreadMax to 650 when he changed the code 6 months ago. There cold be a commit message that references it, but that's more disconnected from the change that just slapping a comment on top that says why.

I agree that code review for configuration changes is necessary. That same code review process can ensure that the comments in the config file are also correct.

[DCoder]

> It can't help you figure out why Bill (who left the company a while back) set ThreadMax to 650 when he changed the code 6 months ago. There cold be a commit message that references it, but that's more disconnected from the change that just slapping a comment on top that says why.

Also worth noting is that not all config files are committed to version control as-is. If a deployment process bakes the config file from variables, it can be even more disconnected and difficult to find the change.

[mlthoughts2018]

The size of the project is a red herring in your comment. People document command line options, ENV settings, etc., in huge projects all the time. It has absolutely no bearing on whether comments belong inside of config files.

[UncleEntity]

> Config files being modified by anyone should be going through code review.

Yeah, I'll put in a PR for my local Transmission config file and see how far that gets me ;)

Config files should be understandable and readable by the end users so they can customize their local installs.

[mlthoughts2018]

This is silly. If an app like Transmission expects end users to modify a config file locally as the means to add customized settings, that’s a seriously bad design. Why not provide documentation about command-line arguments or ENV variables it would look for for end user customizeability. A settings file where you need to know the meaning as you read the file is among the worst ways to solve it.