feat: Add support for *args to AliasMap

[matts1]

This is required in order to support command aliases as functions, because they will require the following to be supported:

'upload()' = ["upload", "@"]
'upload(r)' = [["fix", "$r"], ["git", "push", "--change", "$r"]]

Here, jj upload would need to map to the first, jj upload foo would need to map to the second, and jj upload foo --bar would also need to map to the second.

Checklist

If applicable:

• I have updated CHANGELOG.md
• I have updated the documentation (README.md, docs/, demos/)
• I have updated the config schema (cli/src/config-schema.json)
• I have added tests to cover my changes

[yuja]

This is required in order to support command aliases as functions, because they will require the following to be supported:

'upload()' = ["upload", "@"]
'upload(r)' = [["fix", "$r"], ["git", "push", "--change", "$r"]]

Here, jj upload would need to map to the first, jj upload foo would need to map to the second, and jj upload foo --bar would also need to map to the second.

These examples don't look like *args. (If they were, upload(*args) should conflict with upload(r, *args).)

Perhaps, we'll need a public API to get AliasFunctionOverloads?

let overloads = map.get_function_overloads("upload")?;
// for `jj upload foo --bar`, max_parameters = ["foo"].len()
// XXX should we pick upload/1 for `jj upload foo bar`?? It might be rather confusing.
let arity = min(overloads.max_arity(), max_parameters);
// If there were upload/0, /1, /3, and max_parameters is 2, I think it's better
// to error out (as ambiguous alias definitions) than falling back to upload/1.
let function = overloads.find_by_arity(arity)?;

[yuja]

'upload()' = ["upload", "@"]
'upload(r)' = [["fix", "$r"], ["git", "push", "--change", "$r"]]

Here, jj upload would need to map to the first, jj upload foo would need to map to the second, and jj upload foo --bar would also need to map to the second.

Oh, but jj upload foo --bar will have to be rewritten to [["fix", "foo"], ["git", "push", "--change", "foo", "--bar"]]? Then, we'll need an explicit *args syntax to specify which command list to copy the remainder arguments to, and only one of the overloads should have *args.

[PhilipMetzger]

just a minor nit from my side, "feature" is not a known topic, it could be dsl_util: or aliases:.

[matts1]

Oh, but jj upload foo --bar will have to be rewritten to [["fix", "foo"], ["git", "push", "--change", "foo", "--bar"]]? Then, we'll need an explicit *args syntax to specify which command list to copy the remainder arguments to, and only one of the overloads should have *args.

My original intention was that every overload would have an implicit *args and we perform a longest prefix match, so given, and:

'upload()' = ["upload", "@"]
'upload(r, blah)' = [["fix", "$r"], ["git", "push", "--change", "$r", "$blah", "$args"]]

upload() ==> upload/0(args=[])
upload(first) ==> upload/0(args=[first])
upload(first, second) ==> upload/2(first, second, args=[])
upload(first, second, third) ==> upload/2(first, second, args=[third])

My logic was going to be:

• If the overload goes to a single command, add an implicit $args at the end if it doesn't exist
• If the overload goes to multiple commands, $args was non-empty, and none of the commands ended with $args, then error out.

Your proposal does work as well, I mostly wanted to avoid the *args in the interest of slimming down the syntax since concern was expressed over making the DSL more complex. However, if we're ok with it, then I can implement it in the following way:

'upload()' = ["upload", "@"]
'upload(r, *args)' = [["fix", "$r"], ["git", "push", "--change", "$r" "$args"]]

This would generate an upload/0 and an upload/1+.

[yuja]

My original intention was that every overload would have an implicit *args and we perform a longest prefix match, so given, and:

'upload()' = ["upload", "@"]
'upload(r, blah)' = [["fix", "$r"], ["git", "push", "--change", "$r", "$blah", "$args"]]

upload() ==> upload/0(args=[])
upload(first) ==> upload/0(args=[first])
upload(first, second) ==> upload/2(first, second, args=[])
upload(first, second, third) ==> upload/2(first, second, args=[third])

My feeling is that choosing a prefix match would lead to random unexpected result. I would rather want to see an error if overloads set is somewhat inconsistent.

BTW, the example above has recursion? upload/0 -> (upload/1 ->) upload/0
(["upload"] might be substituted to ["upload", "@", "@"], but I'm not sure.)

Your proposal does work as well, I mostly wanted to avoid the *args in the interest of slimming down the syntax since concern was expressed over making the DSL more complex. However, if we're ok with it, then I can implement it in the following way:

'upload()' = ["upload", "@"]
'upload(r, *args)' = [["fix", "$r"], ["git", "push", "--change", "$r" "$args"]]

This would generate an upload/0 and an upload/1+.

I don't have a strong feeling about whether *args can be implicit or not, but if it can, I would add it only to the function having the maximum arity.