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by unfunco 17 days ago
I've spent some time thinking about it, and I respectfully disagree.

I don't think a `--sort` flag is a failure of composability, the producer understands image size semantics better than the sort command, you can either bake everything into sort, making it an all encompassing command or you can simplify the previous step with a sort flag.

Your original powershell command is way more verbose and complicated, and maybe that's the price to pay for composability, but I'd rather just use the `--sort` flag and not spend hours or days coming up with some other undocumented and undiscovered way of doing it, the answer is right there ready to be used.

I think my point is that it's a violation of the UNIX principle of doing one thing really well, but I don't think that is a violation of composability.
1 comments
jcgl 17 days ago
Tl;dr: Plain text's bad composability forces the dichotomy that you identify between --sort and sort. I agree with you that --sort often can be a sensible UX choice regardless, but losing out on composable middle ground is strictly a loss in terms of power and expressiveness.

Thanks for taking some time to think about it. Despite my pretty absolute wording in GP, I do think that there's nuance here. But what I want to drive home is that the tight coupling/brittleness inherent in plain text composition systematically limits composition.

What I'm not saying is that every --sort option is bad sign for composition. Like you point at, sometimes it's just a simpler UX to have such an option included with your command. As a matter of fact, you see that in PowerShell sometimes with the -Filter option on various cmdlets.

Plain text's brittleness limits composition by promoting exactly the extremes that you point at (the extremes being overloaded sort, or overloaded producer):

> the producer understands image size semantics better than the sort command, you can either bake everything into sort, making it an all encompassing command or you can simplify the previous step with a sort flag.

I think it should be obvious that baking everything into sort is a bad idea in the general case. Like you say, the producer understands the size semantics better. Moreover, the ergonomics are lousy (see comments by users alloyed and i15e).

Baking everything into --sort is bad because it limits sorting to the producer's own predefined semantics. While arguably better than relying on sort's, the producer won't always have the semantics that the user cares about. E.g. maybe the user wants to analyze the disk space used only on a certain datastore. Maybe some datastores do transparent compression and sorting should be done by physical disk usage. And so on.

These two extremes are basically your only options in a plain text world, but structured data gives you more opportunities for composition. By moving to structured data and eliminating the need for ad-hoc parsing, users and their code can operate at a higher semantic level. In particular, the loose coupling introduced by this approach gives you access to things like lambdas. You're not alone in objecting to PowerShell's verbosity. Here's a terser version that would work if podman image output structured data rather than text, thereby kinda steelmanning this position:

  podman image ls --all |
      sort {podman size -h $_.size} -d
Basically all that has happened is that the plain text->structured parsing was dropped (again, to steelman the structured data vision) and naming conventions were made unix-y.

An alternate version if no specialized podman size command is needed and the sort cmdlet would by default look at an object's size property:

  podman image ls --all |
      sort -d
In many common cases, I think I agree with you that having --size on the producer is pragmatic and fast. A good UX choice. What's bad about plain text is that there is not/cannot be any middle ground between --sort and sort.

Now, tools shouldn't always oblige the user to compose. Composition is frequently not the best UX. But a shell that systematically limits composition is prima facie worse than one that promotes it. And plain text shells do indeed limit composition.

Sorry for the essay.

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