internal utilities to find rust crate and cargo manifest (#399)

* internal functions and tests

* Update R/find_extendr.R

Co-authored-by: Josiah Parry <[email protected]>

* Update R/find_extendr.R

Co-authored-by: Josiah Parry <[email protected]>

---------

Co-authored-by: Josiah Parry <[email protected]>

R/find_extendr.R

@@ -0,0 +1,69 @@
+#' Get path to Rust crate in R package directory
+#'
+#' @param path character scalar, the R package directory
+#' @param error_call call scalar, from rlang docs: "the defused call with which
+#' the function running in the frame was invoked"
+#'
+#' @return character scalar, path to Rust crate
+#'
+#' @examples
+#' \dontrun{
+#' find_extendr_crate()
+#' @keywords internal
+#' @noRd
+#' }
+find_extendr_crate <- function(
+    path = ".",
+    error_call = rlang::caller_call()) {
+  check_character(path, call = error_call, class = "rextendr_error")
+
+  rust_folder <- rprojroot::find_package_root_file(
+    "src", "rust",
+    path = path
+  )
+
+  if (!dir.exists(rust_folder)) {
+    cli::cli_abort(
+      "Could not find Rust crate at {.path rust_folder}.",
+      call = error_call,
+      class = "rextendr_error"
+    )
+  }
+
+  rust_folder
+}
+
+#' Get path to Cargo manifest in R package directory
+#'
+#' @param path character scalar, the R package directory
+#' @param error_call call scalar, from rlang docs: "the defused call with which
+#' the function running in the frame was invoked"
+#'
+#' @return character scalar, path to Cargo manifest
+#'
+#' @examples
+#' \dontrun{
+#' find_extendr_manifest()
+#' @keywords internal
+#' @noRd
+#' }
+find_extendr_manifest <- function(
+    path = ".",
+    error_call = rlang::caller_call()) {
+  check_character(path, call = error_call, class = "rextendr_error")
+
+  manifest_path <- rprojroot::find_package_root_file(
+    "src", "rust", "Cargo.toml",
+    path = path
+  )
+
+  if (!file.exists(manifest_path)) {
+    cli::cli_abort(
+      "Could not find Cargo manifest at {.path manifest_path}.",
+      call = error_call,
+      class = "rextendr_error"
+    )
+  }
+
+  manifest_path
+}

tests/testthat/test-find_extendr.R

@@ -0,0 +1,33 @@
+test_that("find_extendr_crate() returns path to Rust crate", {
+  skip_if_not_installed("usethis")
+
+  path <- local_package("testpkg")
+
+  # capture setup messages
+  withr::local_options(usethis.quiet = FALSE)
+
+  expect_error(find_extendr_crate(), class = "rextendr_error")
+
+  use_extendr(path, quiet = TRUE)
+
+  rust_folder <- find_extendr_crate()
+
+  expect_true(dir.exists(rust_folder))
+})
+
+test_that("find_extendr_manifest() returns path to Cargo manifest", {
+  skip_if_not_installed("usethis")
+
+  path <- local_package("testpkg")
+
+  # capture setup messages
+  withr::local_options(usethis.quiet = FALSE)
+
+  expect_error(find_extendr_manifest(), class = "rextendr_error")
+
+  use_extendr(path, quiet = TRUE)
+
+  manifest_path <- find_extendr_manifest()
+
+  expect_true(file.exists(manifest_path))
+})