autocomplete about rcloud HOT 6 CLOSED

I was looking for autocomplete support for ace earlier but ended up with this issue, which was closed 4 months ago. Then I see this long running thread. I also did find this commit, which just confuses me.

Something tells me that they don't have a great support for autocomplete?

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There's this, which has been merged: ajaxorg/ace#1189

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Yayayay! How do we get the words to complete with?

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There's several steps to this.

First, we need a function that takes the current cursor position and isolates the "relevant R statement". There might be R code that does this (@s-u, help here?). Here are some relevant use cases, where I'm using <> to denote the position of the cursor.

First, trivial cases:

x <- rno<>

This should return rnorm, etc. Then, almost-as-trivial:

x <- 5; y <- rno<>

Then, a little more annoying, since it mixes markdown:

# Some title

A paragraph

```{r}
x <- rno<>

This takes some annoying parsing code duplication with knitr, but I see no way around it.

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Assuming we can isolate the latest incomplete R statement, the next step is to crib the rcompgen.completion function from the R graphical client:

> rcompgen.completion
function (x) 
{
    utils:::.assignLinebuffer(x)
    utils:::.assignEnd(nchar(x))
    utils:::.guessTokenFromLine()
    utils:::.completeToken()
    utils:::.CompletionEnv[["comps"]]
}

With that,

> rcompgen.completion("rno")
[1] "rnorm"

> rcompgen.completion("x <- rnorm(")
[1] "n="    "mean=" "sd="  

> rcompgen.completion("y <- 5; x <- rnorm(")
[1] "n="    "mean=" "sd="  

It's smart enough to pluck the last statement by itself, so it might just be a matter of isolating the last R block.

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Pushing basic support for this. Required a few changes to mode-r.js and ext-language_tools.js which I'm not completely sure about and which will need to be reapplied or rethought the next time we upgrade ace.

(See the commit messages.)

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