Triage Structopt PRs since the fork

[epage]

Discussed in #2658

^{Originally posted by epage August 2, 2021}
Dependabot notified me of a structopt update that included TeXitoi/structopt#483. This seems relevant for clap but made me wonder about the problem generally.

When was our last sync-up with structopt and how do we track it so things don't fall through the cracks for future changes?

[epage]

ea76fa1 is the last commit in https://github.com/clap-rs/clap_derive/commits/master?after=acea444f962a0d7c8126273739d4df8bdb152624+34&branch=master from purely structopt. It looks like some fixes went in since then but unsure which

Post fork, already ported

• Automatic naming of fields and subcommands TeXitoi/structopt#143
• Fix up some docs about argument renaming. TeXitoi/structopt#148
• Introduce smarter parsing of doc comments. TeXitoi/structopt#146
• Fix invalid structopt syntax error message TeXitoi/structopt#154
• Fix spelling: occurences -> occurrences, TeXitoi/structopt#158
• Remove line-ending periods from short help. TeXitoi/structopt#161
• TeXitoi/structopt@3d5f9bd
• add completions generation example TeXitoi/structopt#169
• Fix misspelling of "dependencies" TeXitoi/structopt#186
• Support Option<Option<T>> field types TeXitoi/structopt#190
• Support Option<Vec<T>> field type TeXitoi/structopt#191
• Optionally add paw support for structopt as a feature TeXitoi/structopt#192
• Update deprecated function and provide more info about the parsing error TeXitoi/structopt#193
• Improve ChangeLog as suggested by @ErichDonGubler TeXitoi/structopt#194
• Docs: tell about possible literals use for attribute values TeXitoi/structopt#195
• [Casing] Change default from verbatim to kebab. TeXitoi/structopt#204
• Custom attributes parser TeXitoi/structopt#198
• Add example for environment variables TeXitoi/structopt#216
• Support skipping struct fields TeXitoi/structopt#213
• Explicitly specify the Result type TeXitoi/structopt#218
• Add documentation for env TeXitoi/structopt#221
• Now error messages highlight the error location TeXitoi/structopt#225
• Fix a warning TeXitoi/structopt#231
• Update keyvalue example TeXitoi/structopt#234
• Update and improve documentation TeXitoi/structopt#236
• Fix structopt-derive permissions TeXitoi/structopt#239
• Fix error messages TeXitoi/structopt#244
• Fix #245 TeXitoi/structopt#246
• Emit dummy impls on error TeXitoi/structopt#248
• Fix changelog example TeXitoi/structopt#250
• Keep as much span info as possible TeXitoi/structopt#252
• Support skip = value syntax TeXitoi/structopt#260
• Add from_flag parser TeXitoi/structopt#271
• docs: observes that the trait is more than from_args TeXitoi/structopt#275
• Fix parse for OptionVec ref pull #191 TeXitoi/structopt#279
• Fix #269 and #265 TeXitoi/structopt#278
• Pass the try_from_str functions a &str instead of a &String. TeXitoi/structopt#282
• Fix #283 TeXitoi/structopt#284
• Add an example of a negative flag (i.e. --no-verbose) TeXitoi/structopt#281
• Handle special types correctly TeXitoi/structopt#287
• Handle inter-expansion top-level args properly TeXitoi/structopt#290
• Prohibit positional bool TeXitoi/structopt#293
• Introduce #[structopt(rename_all_env)] TeXitoi/structopt#302
• Consistent doc comments TeXitoi/structopt#296
• Propagate no version TeXitoi/structopt#313
• Default value TeXitoi/structopt#312
• Issue 324 TeXitoi/structopt#325
• Flatten for enums TeXitoi/structopt#334
• Introduce #[structopt(external_subcommand)] TeXitoi/structopt#314
• Flatten for enums TeXitoi/structopt#334
• Further improve error messages TeXitoi/structopt#346
• Fix verbatim_doc_comment on fields TeXitoi/structopt#342
• v0.3.14 TeXitoi/structopt#381
• Remove unnecessary braces TeXitoi/structopt#399
• Fix/matches span TeXitoi/structopt#400
• Flattening a subcommand now panics with a meaningful error message TeXitoi/structopt#401

Start of new port series

• Allow #[flatten] fields to have doc comments but ignore them (comments) TeXitoi/structopt#414, see test(derive): Port structopt flatten coverage #2821
• Add support for lower/upper in rename_all TeXitoi/structopt#412, see feat(derive): Add support for lower/upper in rename_all #2822
• v0.3.20 TeXitoi/structopt#440, re-implemented in fix(clap_derive): Unwrap syn::TypeGroup when checking field types #1992
• Bugfix TeXitoi/structopt#448, see fix(derive): Subcommands not working within macro_rules #2823
• Fix explanation on optional string list argument TeXitoi/structopt#450, docs(derive): Fix explanation on optional string list argument #2824
• add basic support for generic structs and enums TeXitoi/structopt#483, split out into Deriving for generic structs #2769
• Fix the problem where the build fails due to the ambiguous type of map TeXitoi/structopt#491, see fix(derive): Fix the problem where the build fails due to the ambigous type of map #2825
• Add skip attribute support for enum variants TeXitoi/structopt#494, see feat(derive): Add skip attribute support for enum variants #2826

[epage]

@pksunkara and @CreepySkeleton since you two were involved a lot during the late stages of clap_derive, if its quick to do a scan to see what is already ported to clap_derive, that'd be appreciated. If not, I'm fully willing to take on doing this deep dive.

[epage]

Looks like I found the point of divergence. We have everything up to 401 and need 414 and after

[pksunkara]

• No coverage for test

[epage]

* [ ]  No coverage for [test](https://github.com/TeXitoi/structopt/pull/401/files#diff-57e8e1f836204e3d43fdd26c8c05d8aa25edc6db8c921f99f5d482c3f56e05a9R134)

I'm not even sure what that is trying to test; I forgot what structopt does when flattening in that context.

As for clap_derive, we don't even allow an enum to flatten a struct, its a compiler error due to mismatched types. Of the various combinations of bad flatten and subcommand, it looks like the only one we cover is

#[derive(clap::Parser)]
struct Opt {
    #[clap(flatten)]
    sub: SubCmd,
}

#[derive(clap::Parser)]
enum SubCmd {}

fn main() {}

I'm mixed on the value of expanding out the rest of the combinations but either way, don't think it would block 3.0.

[epage]

I'm delegating the generics work to #2769 which means we are done or practically done with this. Rather than this lingering on for each new issue, I'm going to go ahead and close it. We can create new issues for each additional structopt porting effort and prioritize accordingly.

[pksunkara]

As for clap_derive, we don't even allow an enum to flatten a struct, its a compiler error due to mismatched types.

Yeah, we need an UI test for that.