R: Create a Result Descriptor by Recording Effects of an Expression Evaluation¶

Description¶

Evaluates an expression and records its direct and indirect effects: the resulting value as well as the information whether any errors, warnings, or messages are generated and if anything is printed on stdout or stderr.

Usage¶

R(expr, ..., envir = parent.frame())

Arguments¶


`expr`	expression to be evaluated
`...`	further arguments to be passed to `P`
`envir`	environment where `expr` is to be evaluated

Details¶

Note that messages, warnings, and errors are typically written to stderr, but these are considered separately here. In other words, when testing expectations with E, e.g., the reference stderr should not include the anticipated diagnostic messages.

There may be other side effects, such as changing the state of the random number generator, modifying options or environment variables, modifying the calling or global environment (e.g., creating new global variables), attaching objects onto the search part (e.g., loading package namespaces), or plotting, but these will not be captured, at least, not by the current version of the realtest package.

Value¶

A list of class realtest_descriptor, see P, which this function calls. The additional named component expr gives the expression that generated the value. Moreover, args gives a named list of objects that appeared in expr (not including functions called).

If an effect of particular kind does not occur, it is not included in the resulting list. stdout, stderr, and error are at most single strings.

When an error occurs, value is NULL.

Author(s)¶

Marek Gagolewski

Examples¶

y <- 1:10; R(sum(y^2))
## $value
## [1] 385
## 
## $expr
## sum(y^2)
## 
## $args
## $args$y
##  [1]  1  2  3  4  5  6  7  8  9 10
## 
## 
## attr(,"class")
## [1] "realtest_descriptor" "realtest"
R(cat("a bit talkative, innit?"))
## $value
## NULL
## 
## $sides
## $sides$stdout
## [1] "a bit talkative, innit?"
## 
## 
## $expr
## cat("a bit talkative, innit?")
## 
## attr(,"class")
## [1] "realtest_descriptor" "realtest"
R(sqrt(c(-1, 0, 1, 2, 4)))
## $value
## [1]      NaN 0.000000 1.000000 1.414214 2.000000
## 
## $sides
## $sides$warning
## [1] "NaNs produced"
## 
## 
## $expr
## sqrt(c(-1, 0, 1, 2, 4))
## 
## attr(,"class")
## [1] "realtest_descriptor" "realtest"
R(log("aaaargh"))
## $value
## NULL
## 
## $sides
## $sides$error
## [1] "non-numeric argument to mathematical function"
## 
## 
## $expr
## log("aaaargh")
## 
## attr(,"class")
## [1] "realtest_descriptor" "realtest"
R({
    cat("STDOUT"); cat("STDERR", file=stderr()); message("MESSAGE");
    warning("WARNING"); warning("WARNING AGAIN"); cat("MORE STDOUT");
    message("ANOTHER MESSAGE"); stop("ERROR"); y; "NO RETURN VALUE"
})
## $value
## NULL
## 
## $sides
## $sides$error
## [1] "ERROR"
## 
## $sides$warning
## [1] "WARNING"       "WARNING AGAIN"
## 
## $sides$message
## [1] "MESSAGE"         "ANOTHER MESSAGE"
## 
## $sides$stdout
## [1] "STDOUTMORE STDOUT"
## 
## $sides$stderr
## [1] "STDERR"
## 
## 
## $expr
## {
##     cat("STDOUT")
##     cat("STDERR", file = stderr())
##     message("MESSAGE")
##     warning("WARNING")
##     warning("WARNING AGAIN")
##     cat("MORE STDOUT")
##     message("ANOTHER MESSAGE")
##     stop("ERROR")
##     y
##     "NO RETURN VALUE"
## }
## 
## $args
## $args$y
##  [1]  1  2  3  4  5  6  7  8  9 10
## 
## 
## attr(,"class")
## [1] "realtest_descriptor" "realtest"