A question regarding tools that output to stdout (expand/unexpand)

[srfsh]

expand(1) and its close friend unexpand(1) are common Unix utilities that convert between tabs and spaces. They are quite handy tools that follow the unix principle well and allows one to workaround the restrictions of an over-opinionated formatter when it strongly insists on a particular indentation format, as is the case with dart, go, and so on.

One particular issue with these tools is that they do not provide an option for the effects of conversion to occur in-place, unlike the common option of -i of sed(1). Normally this isn't such an issue when one is dealing with a relatively small (as in short-termed) task. Although that might be considered a feature (as in piping), it causes a discomfort when using it with tools such as treefmt. The best I've come up with is to utilize these tools through an intermediate script directly embedded in the config file of treefmt using some help from sponge(1). Though I wonder if this really the best option one can come up with? Are there any other alternative to these tools that are widely available that supports an in-place replacement? Maybe some of you might already have figured this out using sed -i. In that case, I would like to hear from you!

Thanks!

[jfly]

The best I've come up with is to utilize these tools through an intermediate script directly embedded in the config file of treefmt using some help from sponge(1).

For the record, this sounds like the correct thing to do. From https://treefmt.com/latest/reference/formatter-spec/:

If the formatter you would like to use doesn't comply with the rules, it's often possible to create a wrapper script that transforms the usage to match the specification.

[srfsh]

For what is worth, I would like to share what I was able to come up with. I use the -nix counterpart directly, but one can easily apply this to the non-nix (this) part:

			settings.formatter.spc2tab = {
				enable = true;
				command = lib.getExe pkgs.gnused;
				options = ["-Ei" '':a;s,^(\t*) {2},\1\t,;ta''];
				includes = ["*.dart"];
				priority = 1;
			};
			settings.formatter.spc4tab = {
				enable = true;
				command = lib.getExe pkgs.gnused;
				options = ["-Ei" '':a;s,^(\t*) {4},\1\t,;ta''];
				includes = ["*.gradle" "*.xml"];
				priority = 1;
			};

In my particular use case, I didn't need to convert tabs to spaces, but one probably can figure out from the regex how to do that. Hope it is helpful to someone on the interwebs.