fix(build): build packages requiring newer R on compatible minors (#216)

local/newer-r-helpers.R

@@ -0,0 +1,75 @@
+# Evaluate every R constraint, including patch-level and upper bounds.
+r_requirement_satisfied <- function(depends, r_version) {
+  if (is.na(depends) || !nzchar(trimws(depends))) {
+    return(TRUE)
+  }
+  entries <- trimws(strsplit(depends, ",", fixed = TRUE)[[1L]])
+  entries <- entries[grepl("^R(\\s|\\(|$)", entries)]
+  all(vapply(
+    entries,
+    function(entry) {
+      if (entry == "R") {
+        return(TRUE)
+      }
+      match <- regmatches(
+        entry,
+        regexec(
+          "^R\\s*\\(\\s*(>=|<=|==|>|<)\\s*([0-9]+(?:[.-][0-9]+)*)\\s*\\)$",
+          entry,
+          perl = TRUE
+        )
+      )[[1L]]
+      if (length(match) != 3L) {
+        stop("Cannot parse R dependency: ", entry)
+      }
+      comparison <- utils::compareVersion(r_version, match[3L])
+      switch(
+        match[2L],
+        ">=" = comparison >= 0L,
+        "<=" = comparison <= 0L,
+        "==" = comparison == 0L,
+        ">" = comparison > 0L,
+        "<" = comparison < 0L
+      )
+    },
+    logical(1L)
+  ))
+}
+
+# Use unfiltered current CRAN metadata: available.packages() would hide exactly
+# the packages that cannot run under the primary interpreter.
+# Propagate R incompatibility through required dependencies, not Suggests.
+newer_r_candidates <- function(db, primary_r, target_r) {
+  db <- as.data.frame(db, stringsAsFactors = FALSE)
+  # CRAN also lists R-specific Recommended copies (e.g. Matrix for R-devel).
+  # Prefer the ordinary contrib record, or a future-R copy can incorrectly
+  # block every package depending on Matrix on all released interpreters.
+  if ("Path" %in% names(db)) {
+    db <- db[order(!is.na(db$Path) & nzchar(db$Path)), , drop = FALSE]
+  }
+  db <- db[!duplicated(db$Package), , drop = FALSE]
+  deps <- tools::package_dependencies(
+    packages = db$Package,
+    db = as.matrix(db),
+    which = c("Depends", "Imports", "LinkingTo"),
+    recursive = FALSE
+  )
+  supported <- function(version) {
+    ok <- vapply(db$Depends, r_requirement_satisfied, logical(1L), version)
+    repeat {
+      blocked <- db$Package[!ok]
+      next_ok <- ok &
+        !vapply(deps, function(x) any(x %in% blocked), logical(1L))
+      if (identical(ok, next_ok)) {
+        return(ok)
+      }
+      ok <- next_ok
+    }
+  }
+  selected <- !supported(primary_r) & supported(target_r)
+  if ("OS_type" %in% names(db)) {
+    selected <- selected & (is.na(db$OS_type) | db$OS_type != "windows")
+  }
+  result <- db[selected, c("Package", "Version"), drop = FALSE]
+  result[order(result$Package), , drop = FALSE]
+}