Expand Session watcher to help auto complete with NSE (tidyverse syntax)

[gowerc]

It would be awesome if the session watchers autocomplete could be expanded to work with non-standard evaluation for example when using dplyr's mutate/select/etc.

I.e. when writing something like:

iris %>%
    select( 

Then have the auto-complete popup with the list of variables within the iris dataset.

[gowerc]

For reference Rstudios implementation of this simply looks at the top most object for which names to use in the autocomplete, for example

As you can see Rstudio just offers all the names of iris in the autocomplete even though none of them exist after the gather() command. Having said that it does have some sense of context as you can see the newly created variable is available in the list. I think even if it was possible to just get the initial object variables listed (ignoring newly created ones) it would be a big help to development !

[gowerc]

At @andycraig & @renkun-ken ,

Which files are related to the current session watcher autocomplete. For example when session watcher is enabled I am able to do this:

But I'm struggling to work out where in the code provides this functionality

[renkun-ken]

On mobile now. If I remember correctly, The session watcher completion is implemented in extension.ts: provideCompletionItems, getBracketCompletionItems, etc.

Please take a look at https://github.com/Ikuyadeu/vscode-R/blob/master/src/extension.ts#L224-L316.

[randy3k]

FYI, it is how RStudio implemented it: https://github.com/rstudio/rstudio/blob/7fd3ff2ba1b579952baceaddd6fcb2ca4c88d186/src/cpp/session/modules/SessionRCompletions.R#L1963

[renkun-ken]

@gowerc I come up with an easy approach to this at https://github.com/renkun-ken/languageserver/tree/token-completion which simply put all symbols that appear in the same document into the completion list, which will be helpful to complete symbols that already appear in the document, including symbols in the pipelines.

You might have a try on this any let me know if this is helpful.

[gowerc]

Thanks for looking into this, will try and find some time to have a play !

[renkun-ken]

To provide completion items in a pipe expression, without a parser, it is a bit trickier to detect the names of the variables to show completions, although we already have the names() of all variables in the global environment in globalenv.json created by the session watcher. I suggest we do the following:

my_dt %>%
  mutate(var3 = test) %>%
  select(var1, var2, var3)

As a starting point, we should detect my_dt in this case, and hopefully var3 in the future.

[danielbasso]

My totally abstract idea by now is to dynamically compute names() for the whole pipe chain using only the first row of the dataframe, to make computations fast. Using only the first row shouldn't affect select(), group_by(), summarise() and others. It could affect filter(), but this can be ignored, I guess?

Edit:

Just for curiosity, apparently even with no rows at all dplyr operations function normally. For example:

my_df <- tibble(var1 = c(1,2,3), var2 = c(4,5,6), var3 = c(7,8,9))

my_df %>% 
  filter(var1 == 4) %>% 
  group_by(var2) %>% 
  summarise(var4 = var1 + var2) %>% 
  names()

Correctly returns:

[1] "var2" "var4"

Even with a filter(var1 == 4) that returns no rows at all. Like I said, I have no idea of who feasible is this approach, but I have a felling that this could be 'exploited'.

[renkun-ken]

My totally abstract idea by now is to dynamically compute names() for the whole pipe chain using only the first row of the dataframe, to make computations fast ...

I'm afraid we cannot execute user code in any way because it might have side effects to user sessions. Imagine user in-place mutate or remove columns or execute some code that has important side effects like

my_df %>%
  filter(var == 4) %>%
  select(path) %>%
  remove_files()

[renkun-ken]

@gowerc @danielbasso would you like to try PR #530 by installing the artifact in https://github.com/Ikuyadeu/vscode-R/actions/runs/500273775?