engine_output: An output wrapper for language engine output

Description

If you have designed a language engine, you may call this function in the end to format and return the text output from your engine.

Usage

engine_output(options, code, out, extra = NULL)

Value

A character string generated from the source code and output using the appropriate output hooks.

Arguments

options: A list of chunk options. Usually this is just the object options passed to the engine function; see knit_engines.
code: Source code of the chunk, to which the output hook source is applied, unless the chunk option echo is FALSE.
out: Text output from the engine, to which the hook output is applied, unless the chunk option results is 'hide'
extra: Any additional text output that you want to include.

Details

For expert users, an advanced usage of this function is engine_output(options, out = LIST) where LIST is a list that has the same structure as the output of evaluate::evaluate(). In this case, the arguments code and extra are ignored, and the list is passed to knitr::sew() to return a character vector of final output.

Examples

Run this code

library(knitr)
engine_output(opts_chunk$merge(list(engine = "Rscript")),
    code = "1 + 1", out = "[1] 2")
engine_output(opts_chunk$merge(list(echo = FALSE, engine = "Rscript")),
    code = "1 + 1", out = "[1] 2")

# expert use only
engine_output(opts_chunk$merge(list(engine = "python")),
    out = list(structure(list(src = "1 + 1"), class = "source"),
        "2"))