Read cargo metadata (#389)

* draft and test

* use expect_type()

* list under utility functions

* document

* check string

* more meaningful test

* update news

* Update NEWS.md

Co-authored-by: Ilia Kosenkov <[email protected]>

---------

Co-authored-by: Ilia Kosenkov <[email protected]>

NAMESPACE

@@ -14,6 +14,7 @@ export(document)
 export(eng_extendr)
 export(eng_extendrsrc)
 export(make_module_macro)
+export(read_cargo_metadata)
 export(register_extendr)
 export(rust_eval)
 export(rust_function)

NEWS.md

@@ -17,6 +17,8 @@
 * Fixed an issue in `rust_source()` family of functions that prevented usage of `r#` escape sequences in Rust function names (#374)
 * `use_cran_defaults()` now checks the `SystemRequirements` field in the `DESCRIPTION` file for cargo and rustc. It will display installation instructions if either is missing or provide the minimum required version if the installed version is outdated.
 * Added `use_msrv()` to aid in specifying the minimum supported rust version (MSRV) for an R package
+* Added `read_cargo_metadata()` to retrieve Cargo metadata for packages and
+  workspaces. (#389)
 
 # rextend 0.3.1
 

R/read_cargo_metadata.R

@@ -0,0 +1,46 @@
+#' Retrieve metadata for packages and workspaces
+#'
+#' @param path character scalar, the R package directory
+#'
+#' @details
+#' For more details, see
+#' \href{https://doc.rust-lang.org/cargo/commands/cargo-metadata.html}{Cargo docs}
+#' for `cargo-metadata`. See especially "JSON Format" to get a sense of what you
+#' can expect to find in the returned list.
+#'
+#' @return `list`, including the following elements:
+#' - "packages"
+#' - "workspace_members"
+#' - "workspace_default_members"
+#' - "resolve"
+#' - "target_directory"
+#' - "version"
+#' - "workspace_root"
+#' - "metadata"
+#'
+#' @export
+#'
+#' @examples
+#' \dontrun{
+#' read_cargo_metadata()
+#' }
+#'
+read_cargo_metadata <- function(path = ".") {
+  check_string(path, class = "rextendr_error")
+
+  root <- rprojroot::find_package_root_file(path = path)
+
+  rust_folder <- normalizePath(
+    file.path(root, "src", "rust"),
+    winslash = "/",
+    mustWork = FALSE
+  )
+
+  out <- processx::run(
+    "cargo",
+    args = c("metadata", "--format-version=1", "--no-deps"),
+    wd = rust_folder
+  )
+
+  jsonlite::fromJSON(out[["stdout"]])
+}

_pkgdown.yml

@@ -29,3 +29,4 @@ reference:
   - to_toml
   - make_module_macro
   - rust_sitrep
+  - read_cargo_metadata

tests/testthat/test-read_cargo_metadata.R

@@ -0,0 +1,38 @@
+test_that("read_cargo_metadata() returns crate or workspace metadata", {
+  skip_if_not_installed("usethis")
+
+  path <- local_package("testpkg")
+
+  # capture setup messages
+  withr::local_options(usethis.quiet = FALSE)
+
+  use_extendr(path, quiet = TRUE)
+
+  out <- read_cargo_metadata(path)
+
+  expect_type(out, "list")
+
+  expect_equal(
+    out[["packages"]][["name"]],
+    "testpkg"
+  )
+
+  expect_equal(
+    out[["packages"]][["version"]],
+    "0.1.0"
+  )
+
+  expect_equal(
+    out[["packages"]][["dependencies"]][[1]][["name"]],
+    "extendr-api"
+  )
+
+  expect_equal(
+    out[["workspace_root"]],
+    normalizePath(
+      file.path(path, "src", "rust"),
+      winslash = "\\",
+      mustWork = FALSE
+    )
+  )
+})