add checks for namespace versions (#41)

R/namespace.R

@@ -5,18 +5,68 @@
 #' @examples
 #' isTRUE(require_namespace("base")) # returns invisibly
 #' try(require_namespace("1package")) # (using a purposefully bad name)
+#' require_namespace("base", "utils")
+#' try(require_namespace("base>=3.5", "utils>4.0", "fuj==10.0"))
 #' @export
 require_namespace <- function(package, ...) {
-  pkgs <- c(package, ...)
-  for (pkg in pkgs) {
-    if (!isTRUE(try(requireNamespace(pkg, quietly = TRUE), silent = TRUE))) {
-      stop(cond_namespace(pkg))
-    }
+  package <- c(package, ...)
+  comparisons <- regmatches(package, regexec(">=?|<=?|==", package))
+  splits <- strsplit(package, comparisons, fixed = TRUE)
+
+  for (i in seq_along(package)) {
+    do_require_namespace(
+      package = splits[[i]][1],
+      version = splits[[i]][2],
+      operator = comparisons[[i]]
+    )
   }
 
   invisible(TRUE)
 }
 
+# helpers -----------------------------------------------------------------
+
+do_require_namespace <- function(package, version, operator) {
+  tryCatch(
+    loadNamespace(package),
+    packageNotFoundError = function(e) {
+      stop(cond_namespace(package))
+    }
+  )
+
+  if (identical(operator, character())) {
+    return()
+  }
+
+  operator <- match.arg(trimws(operator), c(">", ">=", "==", "<=", "<"))
+  version <- as.package_version(version)
+
+  package_version <- function(package) {
+    # already loaded the namespace
+    if (package == "base") {
+      return(getRversion())
+    }
+
+    as.package_version(
+      get("spec", get(".__NAMESPACE__.", getNamespace(package)))[["version"]]
+    )
+  }
+
+  if (switch(
+    operator,
+    `>` = package_version(package) > version,
+    `>=` = package_version(package) >= version,
+    `==` = package_version(package) == version,
+    `<=` = package_version(package) <= version,
+    `<` = package_version(package) < version,
+    any = TRUE
+  )) {
+    stop(cond_namespace_version(package, version, operator))
+  }
+}
+
+# conditions --------------------------------------------------------------
+
 cond_namespace <- function(package) {
   new_condition(
     msg = sprintf(
@@ -26,3 +76,15 @@ cond_namespace <- function(package) {
     class = "namespace"
   )
 }
+
+cond_namespace_version <- function(package, version, operator) {
+  new_condition(
+    msg = sprintf(
+      "Package '%s' not found with version %s%s",
+      package,
+      operator,
+      format(version)
+    ),
+    class = "namespace_version"
+  )
+}