{survival} needs to be attached for npsurv() to work

[halhen]

It seems like {survival} needs to be attached via library(rms) or library(survival) for npsurv() to work. Issue found in a package where I don't attach packages but use package:: namespacing.

Steps to reproduce; from a fresh session.

> set.seed(1)
> data <- data.frame(var = sample(c("a", "b"), 10, replace = TRUE), surv = survival::Surv(1:10, runif(10) < 0.5))
> data
   var surv
1    a    1
2    b    2
3    a   3+
4    a    4
5    b   5+
6    a    6
7    a   7+
8    a   8+
9    b    9
10   b  10+
> rms::npsurv(surv ~ var, data = data)
Error in survfit(formula = surv ~ var, data = data) : 
  could not find function "survfit"
> library(survival)
> rms::npsurv(surv ~ var, data = data)
Call: rms::npsurv(formula = surv ~ var, data = data)

      n events median 0.95LCL 0.95UCL
var=a 6      3      6       4      NA
var=b 4      2      9       2      NA

Workaround: I #' @import survival and devtools::document() in my package to have {survival} attached.