Input completion

[joshbax189]

Adds completion, supporting both company and completion-at-point completion styles out-of-the-box.

Call either completion-at-point or company-manual-begin to get completions.

Limitations

• does not complete keywords, e.g. "for", "function" etc (although this could be enabled within company)
• completion-at-point does not complete global values, i.e. when the prompt is empty

How it works

At a high level, it sends the current user input followed by TAB to the REPL, then turns the response back into a list of candidates.

The completion responses are dispatched to listening callbacks, which contain their own state in closures. The callbacks represent a specific completion, e.g. "complete 'Array.' with a list of properties", or "clear the input". This async design means we avoid blocking while waiting for responses, so completion does not feel laggy.

Specifically, js-comint--async-output-filter is the dispatcher: it diverts output to a hidden buffer js-comint--completion-buffer when there are callbacks in js-comint--completion-callbacks and when the input and prompt positions match. Each of js-comint--get-completion-async and js-comint--clear-input-async are listener "factories", which send some input and register a callback to handle the expected response, implicitly hiding the output until they are completed.

[redguardtoo]

You don't need require company explicitly. The standard practice is using completing-read api which supported by company-mode. Could you also squash your commits into one commit which is easier for my review?

[joshbax189]

Could you also squash your commits into one commit which is easier for my review?

Done

The standard practice is using completing-read api which supported by company-mode

I think you mean completion-at-point not completing-read?

The reason I chose to add company-js-comint is because I designed the completion to use async functions. For example, see the signature js-comint--get-completion-async (input-string callback): the completion results are used as an argument to callback. This already matches the company API.

completion-at-point-function is a function that takes no arguments and (synchronously) returns (START END COLLECTION . PROPS). To convert js-comint--get-completion-async to a completion-at-point function I call the async function then poll for a result, see the implementation of js-comint--capf (note CAPF = completion-at-point function).

So, rather than having company-capf (async) call js-comint--capf (sync) call js-comint--get-completion-async (async), I just directly provide a company backend and enable it if company is loaded.

If company is not loaded, then js-comint--capf is used, so you can use completion with no extra packages installed.

[redguardtoo]

Thanks.