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Quarto code-cell helpers

Source: R/cell.R
code_cell.Rd

[Experimental]

Usage

is_code_cell(x)

cell_engine(x)

cell_options(x)

cell_code(x)

cell_label(x)

set_cell_options(x, ...)

set_cell_label(x, value)

collect_code(x, engine = NULL, eval_only = FALSE, label_comments = TRUE)

Arguments

x

For the accessors and setters, a pandoc_code_block: the accessors return empty / NA on a non-cell, and the setters require an executable cell (braced engine). For collect_code(), any node or document to gather cells from.

...

For set_cell_options(), named key = value option pairs.

value

For set_cell_label(), the new label string.

engine

For collect_code(), keep only cells with this engine.

eval_only

For collect_code(), drop cells whose eval option is FALSE.

label_comments

For collect_code(), prefix each cell's code with a # <label> comment when it has a label.

Value

Accessors return a scalar (or named list, for cell_options()); setters return a new pandoc_code_block; collect_code() returns a single string.

Details

A Quarto executable cell parses to a pandoc_code_block whose engine is carried as a braced class ({r}, {python}, {ojs}, ...) and whose cell options live in leading #| (or //| / --|) comment lines inside @text. None of that is surfaced by the raw node, so these helpers read and edit it: they are the q2r analog of mq's .code(lang) selector and of parsermd's rmd_node_engine() / rmd_node_label() / rmd_node_options() family.

A plain fenced code block (```r, class r with no braces) is not a cell: is_code_cell() is FALSE, cell_engine() is NA, and cell_options() is empty.

Helpers

  • is_code_cell(x) TRUE when x is an executable cell (a pandoc_code_block with a braced engine class).

  • cell_engine(x) the engine name ("r", "python", ...) or NA.

  • cell_label(x) the label option, falling back to @attr@id, or NA.

  • cell_code(x) the cell body with the leading option lines stripped.

  • cell_options(x) the #| options parsed from YAML into a named list.

  • set_cell_options(x, ...) returns a new cell with options set from named key = value pairs (a NULL value removes that option, mirroring set_attr()).

  • set_cell_label(x, value) convenience for set_cell_options(x, label = value).

  • collect_code(x, ...) tangles the code of every cell under x into one string.

Inside a select_nodes() / map_nodes() predicate the mask also exposes is_code_cell() (zero-argument, tests the current node) and has_option(key) / has_option(key, value), so select_nodes(doc, is_code_cell() & has_option("eval", FALSE)) works.

Examples

if (FALSE) { # \dontrun{
doc = parse_qmd("```{r}\n#| label: fig-1\n#| echo: false\nplot(1)\n```\n")
cell = select_first(doc, is(pandoc_code_block))
cell_engine(cell)
cell_options(cell)
set_cell_options(cell, echo = TRUE, eval = NULL)
} # }