[RFC]: add support for signature argument hints in the REPL

[kgryte]

Description

This RFC proposes adding support for signature argument hints in the REPL. The idea is to extend the preview completion functionality introduced in #1832 to display function and method signatures (i.e., parameter lists), similar to what modern IDEs support when leveraging TypeScript declarations and JSDoc comments.

Once a user types foo(, modern IDEs can read, e.g., TypeScript overloads to display parameter hints (e.g., foo(<|> beep: string, boop?: number ), where <|> indicates the cursor. In this RFC, the proposal is that we should add similar support to the REPL where everything after the cursor would be greyed out text, similar to preview completions introduced in #1832. However, one key difference is that the signatures are purely to serve as hints; once a user begins typing a literal or identifier for a parameter, the hint for that parameter should disappear and normal TAB completion should be possible. After a user has finished and typed , in the example above, we'd display another hint for the second parameter.

We already have a database of signatures, as derived from TypeScript declarations (see https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/repl/signature). Currently, you can only see these signatures using the info command. In the REPL,

In [1]: info( typedarray )

will display a list of overloads and one line descriptions. We could potentially leverage the database to support signature argument hints.

Related Issues

• feat: add auto-completion preview for REPL #1832

Questions

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Checklist

• I have read and understood the Code of Conduct.
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• The issue name begins with RFC:.