beginning refactor of nse semantics for #74

R/nse.R

@@ -0,0 +1,45 @@
+#' Create a data mask rectangular data structures in Bioconductor
+#' 
+#' @description Tidy evaluation for rectangular 
+#' data structures in Bioconductor.
+#' @details This is the backend for non-standard evaluation 
+#' in `plyranges` and is used to provide semantics for non-standard
+#' evaluation used throughout the grammar. Generally,
+#' you will not need to interact with this function directly,
+#' but it can be useful if you're planning on extending
+#' `plyranges` functionality. 
+#' 
+#' @seealso [rlang::new_data_mask()], [rlang::eval_tidy()] 
+bc_data_mask <- function(data) {
+  # extract the namespace of the class
+  pkg_scope <- rlang::pkg_env(packageSlot(class(data)))
+
+  # place the generics at the top of the mask
+  top <- bioc_generics()
+  top <- rlang::new_environment(top)
+  # enclose the mcols as middle
+  mcols_names <- names(mcols(data))
+  mcols_fn <- lapply(mcols_names,
+                   function(nm) {
+                     function() mcols(data)[[nm]]
+                   })
+  names(mcols_fn) <- mcols_names
+
+  mid <- rlang::env(top)
+  rlang::env_bind_active(mid, !!!mcols_fn)
+  # bottom is the vector
+  vec_names <- parallelVectorNames(data)
+  vec_fn <- lapply(vec_names,
+                   function(nm) {
+                     getter <- rlang::env_get(pkg_scope, nm)
+                     function() getter(data)
+                   })
+  names(vec_fn) <- vec_names
+  bottom <- rlang::env(mid)
+  rlang::env_bind_active(bottom, !!!vec_fn)
+
+  mask <- rlang::new_data_mask(bottom, top = top)
+  mask$.data <- rlang::as_data_pronoun(mask)
+  mask
+}
+