Automatically read license field from Cargo.toml #2144

robinmoussu · 2020-09-25T09:49:37Z

Note: this is my first time contributing to clap, and I'm not familiar with the codebase. Please review that I didn't forgot anything.

I recently added support in Cargo for the environment variable CARGO_PKG_LICENSE_FILE in addition to the recently added CARGO_PKG_LICENSE. This commit automatically populate the license field by reading those environment variable.

If both of the environment variable are empty, should we panic!() instead of just returning an empty string? I don't think that panicking is a good idea, since it would possibly break crates that are using the app_from_crate! macro, but I don't know of a better way to add a warning.

This may help a bit with #1768.

robinmoussu · 2020-09-25T10:34:01Z

I realized that this PR bump the MSRV to 1.46 or later (since the environment variables where added in this release). Should I use option_env! instead of the env! macro?

pksunkara

Why would this bump MSRV?

Also, please add some tests.

src/build/app/mod.rs

robinmoussu · 2020-09-25T12:35:00Z

Why would this bump MSRV?

Because cargo < 1.46 doesn't set CARGO_PKG_LICENSE_FILE, likewise cargo < 1.45 for CARGO_PKG_LICENSE. If the environment variable isn't set, the env! macro fails at compile time. This means that this commit requires a MSRV of 1.46 or later as you can see in the results of the CI. If bumping the MSRV is not desirable, it's also possible to use option_env! instead of env! since the former returns None when the environment variable isn't set, while the later panics.

Looking at the Readme, I found that:

clap will officially support current stable Rust, minus two releases, but may work with prior releases as well.

So I think that we should either wait for 2 additional stable releases of rust, or change env! by option_env! before merging this commit.

Also, please add some tests.

I tried to look at the history to know where I should add them, but unfortunately when the macro crate_description!, crate_name! and app_from_crate! were introduced in 4d9a82d no tests where added. Could you please help me to find where I should add them?

pksunkara · 2020-09-29T08:24:41Z

I have created "Rust 1.46" label so that we can look at the issues for it later.

robinmoussu · 2020-09-29T08:52:43Z

Good idea

pksunkara

So, we are setting the license, but where exactly is being used?

You also need to rebase on master now.

examples/08_subcommands.rs

src/macros.rs

pksunkara · 2020-12-08T17:55:15Z

@robinmoussu Do you plan to pick this up?

robinmoussu · 2020-12-08T18:00:32Z

Yes. Sorry the delay. I should have the time this evening.

robinmoussu · 2020-12-08T21:30:07Z

So, we are setting the license, but where exactly is being used?

I didn't realized that it's possible to specify the license (multiple tests where already doing it), but it doesn't seems possible to use it. This is especially weird in new_help.rs where a --license argument is created, but it doesn't have any actions associated (it was modified in 0333380).

pksunkara

You haven't added a test for crate_license which would have caught the issue I mentioned in the other comment. Please do.

src/macros.rs

robinmoussu · 2020-12-08T23:04:32Z

You haven't added a test for crate_license which would have caught the issue I mentioned in the other comment. Please do.

I am relatively surprised, and I think I totally forgot the context of when I wrote this PR. I thought that the notion of "license" was already exposed in clap, but it seems not. I'm working on it.

robinmoussu · 2020-12-08T23:28:56Z

This is a much bigger change than what I expected. And I will not have the time to do it short term. I will finish it (unless someone does it before me) probably in a few months when my current project will no longer have high priority. Here is a list of what is missing:

adding the version in the output of --help and --version (like what ls does)
automatically add an option --license that displays the license if the license is provided and the option doesn't exists (like --help and --version)
if a license file is used, I think its content should be embeded it into the binary, or at least the first line/paragraph to be able to display it correctly (in case the file is named something like "LICENSE.txt").
make it possible to add a license for every supported way in clap (like with the yaml parser, more or less here).

This reverts commit 6898fbd. PR clap-rs#2144 added the `license` field but no consumer has been added since the (like Issue clap-rs#1768). Since this is not ready yet, I am pulling it from the 3.0 release. So far, our main route for pulling a feature from the release has been to put it behind a `unstable-*` feature flag and to create a stablization tracking issue. I chose to instead remove the feature because a write-only field with no effect does not provide values for people to use in as an early access and so doesn't outweight the cost of the extra documentation noise and code noise it creates. Additionally, keeping an `unstable-` feature around when it has such an unknown path (and time table) to stalbization feels like it violates YAGNI. I'm uncertain how much of this feature we can implement and not create a legal trap for users because the crate's license is insufficient for the final artifact's license. I feel our stabliazation process sshould be about iteration and collecting user feedback which this doesn't line up with. When someone is ready to tackle clap-rs#1768, it will be easy to revert this commit and pick up the work again. Fixes clap-rs#3001

pksunkara requested changes Sep 25, 2020

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pksunkara added the E: rust 1.46 label Sep 27, 2020

pksunkara marked this pull request as draft September 27, 2020 21:21

pksunkara removed the E: rust 1.46 label Nov 28, 2020

pksunkara marked this pull request as ready for review November 28, 2020 13:17

pksunkara requested changes Nov 28, 2020

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robinmoussu force-pushed the master branch 2 times, most recently from 9e9b4e8 to 8513891 Compare December 8, 2020 21:53

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robinmoussu force-pushed the master branch from 8513891 to 1c1e6b5 Compare December 8, 2020 22:47

Automatically read license field from Cargo.toml

6898fbd

robinmoussu force-pushed the master branch from 1c1e6b5 to 6898fbd Compare December 8, 2020 23:16

pksunkara merged commit 0a91329 into clap-rs:master Dec 8, 2020

ErichDonGubler mentioned this pull request Oct 30, 2021

doc: show license in CLI help bellboy-dotfiles/bellboy#28

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epage mentioned this pull request Nov 8, 2021

license field is not shown #3001

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epage mentioned this pull request Nov 12, 2021

Revert "Automatically read license field from Cargo.toml" #3016

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Automatically read license field from Cargo.toml #2144

Automatically read license field from Cargo.toml #2144

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Automatically read license field from Cargo.toml #2144

Automatically read license field from Cargo.toml #2144

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