Quarto targets - indicate code chunk that causes error

[arnold-c]

Prework

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Proposal

Thanks for adding Quarto targets - I've been eagerly following the feature progress on this one! Ideally, tar_quarto() would produce a similar error message to tar_render() i.e. specify the lines/code chunk that produce an error (without needing to inspect tar_meta() for quick debugging). Currently it just specifies that there is an error in the pipeline. MWE below altering the vignette example with a spelling error in the code chunk.

targets::tar_dir({  # tar_dir() runs code from a temporary directory.
    # Unparameterized Quarto document:
    lines <- c(
        "---",
        "title: report.qmd source file",
        "output_format: html",
        "---",
        "Assume these lines are in report.qmd.",
        "```{r}",
        # Note the incorrect spelling to cause an error
        "targets::tar_red(data)",
        "```"
    )
    writeLines(lines, "report.qmd")
    # Include the report in a pipeline as follows.
    targets::tar_script({
        library(tarchetypes)
        list(
            tar_target(data, data.frame(x = seq_len(26), y = letters)),
            tar_quarto(report, path = "report.qmd")
        )
    }, ask = FALSE)

    # Run pipeline
    targets::tar_make()
})
#> • start target report
#> ✖ error target report
#> • end pipeline: 2.266 seconds
#> Error : ! System command 'quarto' failed
#> ✖ Problem with the pipeline.
#> ℹ Show errors: tar_meta(fields = error, complete_only = TRUE)
#> ℹ Learn more: https://books.ropensci.org/targets/debugging.html
#> Error:
#> ! problem with the pipeline.

^{Created on 2022-07-01 by the reprex package (v2.0.1)}

[wlandau]

quiet = FALSE in tarchetypes::tar_quarto() prints the Quarto build log to the R console. But otherwise, I'm afraid this is outside my control because the error message generated by the quarto R package is "System command 'quarto' failed".

lines <- c(
  "---",
  "title: 'error'",
  "format: html",
  "editor: source",
  "---",
  "",
  "```{r}",
  "stop('true message')",
  "```"
)
writeLines(lines, "report.qmd")
tryCatch(
  quarto::quarto_render("report.qmd", quiet = TRUE),
  error = function(condition) {
    print(sprintf("Quarto error message: %s", conditionMessage(condition)))
  }
)
#> [1] "Quarto error message: ! System command 'quarto' failed"

^{Created on 2022-07-01 by the reprex package (v2.0.1)}