Install .x etc. into data masks in same way pronouns are

Author: brookslogan

R/grouped_epi_archive.R

@@ -371,14 +371,18 @@ grouped_epi_archive =
 
               quo = quos[[1]]
               f = function(.x, .group_key, .ref_time_value, quo, ...) {
-                data_parent_env = rlang::as_environment(.x)
-                data_env = env(data_parent_env,
-                               .x = .x, .group_key = .group_key,
-                               .ref_time_value = .ref_time_value)
-                # `as_data_mask()` appears to strip off ancestors. We'll need to
-                # do some more work with `new_data_mask()`:
-                data_mask = rlang::new_data_mask(data_env, top = data_parent_env)
-                data_mask$.data <- rlang::as_data_pronoun(.x)
+                # Convert to environment to standardize between tibble and R6
+                # based inputs. In both cases, we should get a simple
+                # environment with the empty environment as its parent.
+                data_env = rlang::as_environment(.x)
+                data_mask = rlang::new_data_mask(bottom = data_env, top = data_env)
+                data_mask$.data <- rlang::as_data_pronoun(data_mask)
+                # We'll also install `.x` directly, not as an
+                # `rlang_data_pronoun`, so that we can, e.g., use more dplyr and
+                # epiprocess operations.
+                data_mask$.x = .x
+                data_mask$.group_key = .group_key
+                data_mask$.ref_time_value = .ref_time_value
                 rlang::eval_tidy(quo, data_mask)
               }
               new_col = sym(names(rlang::quos_auto_name(quos)))

R/methods-epi_archive.R

@@ -681,7 +681,10 @@ group_by.epi_archive = function(.data, ..., .add=FALSE, .drop=dplyr::group_by_dr
 #'   reference time value can be accessed via `.ref_time_value`.
 #' @param ... Additional arguments to pass to the function or formula specified
 #'   via `f`. Alternatively, if `f` is missing, then `...` is interpreted as an
-#'   expression for tidy evaluation. See details of [`epi_slide`].
+#'   expression for tidy evaluation; in addition to referring to columns
+#'   directly by name, the expression has access to a `.data` and `.env`
+#'   pronouns as in `dplyr` verbs, and can also refer to the `.group_key` and
+#'   `.ref_time_value`. See details of [`epi_slide`].
 #' @param before How far `before` each `ref_time_value` should the sliding
 #'   window extend? If provided, should be a single, non-NA,
 #'   [integer-compatible][vctrs::vec_cast] number of time steps. This window