[SPARK-13905][SPARKR] Change signature of as.data.frame() to be consistent with the R base package.

[sun-rui]

What changes were proposed in this pull request?

Change the signature of as.data.frame() to be consistent with that in the R base package to meet R user's convention.

How was this patch tested?

dev/lint-r
SparkR unit tests

[SparkQA]

Test build #53497 has finished for PR 11811 at commit 53cc1d7.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[felixcheung]

if it wasn't a conflict previously, why change it now that it could cause a conflict?

[sun-rui]

R's signature is

as.data.frame(x, row.names = NULL, optional = FALSE, ...)

But current implementation does not support the parameters like row.names, optional:

            if (length(list(...)) > 0) {
              stop(paste("Unused argument(s): ", paste(list(...), collapse = ", ")))
            }

This PR enhance the implementation so that the additional parameters can be honored. This should match R users's usage more.

Also in this PR the as.data.frame versions in the R base package can also be expose and used.

[felixcheung]

make sense - I'd suggest amending JIRA/PR title to reflect this nice additional functionality?

[felixcheung]

looks good!

[shivaram]

LGTM. @sun-rui Sorry for the delay in looking at this. Can you bring this PR up to date with master ?

[sun-rui]

@shivaram, rebased to master.

[SparkQA]

Test build #56314 has finished for PR 11811 at commit c6e881d.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[shivaram]

LGTM. Merging this.