Styling around switch statements

NEWS.md

@@ -47,6 +47,8 @@
 
 - `style_dir()` and `style_pkg()` now apply directory exclusion recursively with 
   `exclude_dirs` (#676).
+- `switch()` now has line breaks after every argument to match the tidyverse 
+  style guide (#722).
 - unary `+` before a function call does not give an error anymore, as before 
   version 1.3.0 (#697).
 - cache is now correctly invalidated when style guide arguments change (#647).

R/rules-line-breaks.R

@@ -209,39 +209,61 @@ set_line_break_after_assignment <- function(pd) {
 #'   not cause a line break after "'('".
 #' @param except_token_before A character vector with text before "')'" that do
 #'   not cause a line break before "')'".
+#' @param force_text_before A character vector with text before "'('" that
+#'   forces a line break after every argument in the call.
 #' @name set_line_break_if_call_is_multi_line
 #' @importFrom rlang seq2
 #' @keywords internal
 NULL
 
-#' @describeIn set_line_break_if_call_is_multi_line Sets line break after
-#'   opening parenthesis.
+#' Sets line break after opening parenthesis
+#'
+#' @details
+#' In general, every call that is multi-line has a line break after the opening
+#' parenthesis. Exceptions:
+#'
+#' * The token right after the parenthesis is a comment, then, the line should
+#'   be broken after the comment only. Governed by `except_token_after`.
+#' * The name of the function called is `ifelse()` or similar, where we can
+#'   allow the condition on the same line as the function name, and we don't
+#'   impose rules on the line breaks for the subsequent arguments. Governed
+#'   by `except_text_before`.
+#' * Some calls like `switch()` statements are always forced to become multi-
+#'   line. Governed by `force_text_before`.
+#'
 #' @keywords internal
-set_line_break_after_opening_if_call_is_multi_line <-
-  function(pd,
-           except_token_after = NULL,
-           except_text_before = NULL) {
-    if (!is_function_call(pd) && !is_subset_expr(pd)) {
-      return(pd)
-    }
-    npd <- nrow(pd)
-    seq_x <- seq2(3L, npd - 1L)
-    is_multi_line <- any(
-      (pd$lag_newlines[seq_x] > 0) |
-        (pd$token[seq_x] == "COMMENT")
+set_line_break_after_opening_if_call_is_multi_line <- function(pd,
+                                                               except_token_after = NULL,
+                                                               except_text_before = NULL,
+                                                               force_text_before = NULL) {
+  if (!is_function_call(pd) && !is_subset_expr(pd)) {
+    return(pd)
+  }
+  has_force_text_before <- pd$text[next_non_comment(pd, 0)] %in% force_text_before
+  if (has_force_text_before) {
+    break_pos <- c(
+      which(lag(pd$token %in% c("','", "COMMENT"))),
+      nrow(pd) # always break before last because this is multi-line
     )
-    if (!is_multi_line) {
+  } else {
+    if (!any(pd$lag_newlines[seq2(3L, nrow(pd))] > 0)) {
       return(pd)
     }
     break_pos <- find_line_break_position_in_multiline_call(pd)
-
-    exception_pos <- c(
-      which(pd$token %in% except_token_after),
-      ifelse(pd$child[[1]]$text[1] %in% except_text_before, break_pos, NA)
-    )
-    pd$lag_newlines[setdiff(break_pos, exception_pos)] <- 1L
-    pd
   }
+  exception_pos <- c(
+    which(pd$token %in% except_token_after),
+    ifelse(pd$child[[1]]$text[1] %in% except_text_before, break_pos, NA)
+  )
+  pd$lag_newlines[setdiff(break_pos, exception_pos)] <- 1L
+  if (has_force_text_before) {
+    first_arg <- which(pd$token == "expr")[2]
+    if (lag(pd$token)[first_arg] != "COMMENT") {
+      pd$lag_newlines[first_arg] <- 0L
+    }
+  }
+  pd
+}
 
 
 #' Find index of the token before which the line should be broken

R/style-guides.R

@@ -142,19 +142,20 @@ tidyverse_style <- function(scope = "tokens",
       # must be after style_line_break_around_curly as it remove line
       # breaks again for {{.
       set_line_break_around_curly_curly = set_line_break_around_curly_curly,
-      set_line_break_after_opening_if_call_is_multi_line = if (strict) {
-        partial(
-          set_line_break_after_opening_if_call_is_multi_line,
-          except_token_after = "COMMENT",
-          except_text_before = c("switch", "ifelse", "if_else")
-        )
-      },
       set_line_break_before_closing_call = if (strict) {
         partial(
           set_line_break_before_closing_call,
           except_token_before = "COMMENT"
         )
       },
+      set_line_break_after_opening_if_call_is_multi_line = if (strict) {
+        partial(
+          set_line_break_after_opening_if_call_is_multi_line,
+          except_token_after = "COMMENT",
+          except_text_before = c("ifelse", "if_else"), # don't modify line break here
+          force_text_before = c("switch") # force line break after first token
+        )
+      },
       remove_line_break_in_fun_call = purrr::partial(remove_line_break_in_fun_call, strict = strict),
       add_line_break_after_pipe = if (strict) add_line_break_after_pipe,
       set_linebreak_after_ggplot2_plus = if (strict) set_linebreak_after_ggplot2_plus

tests/testthat/line_breaks_fun_call/switch_ifelse_etc_no_line_break-in.R

@@ -3,12 +3,45 @@ call(
   3
 )
 
-switch(abc,
-  wei9
+switch(
+  x,
+  a = 2,
+  y = 3
 )
 
-switch(abc,
-  wei9
+
+switch( #
+  x,
+  a = 2,
+  y = 3
+)
+
+
+
+switch(
+  x,
+  a = 2, #
+
+
+  y = 3
+)
+
+
+switch(
+       x,a = 2,
+       y = 3
+)
+
+switch(x,a = 2,
+  y = 3
+)
+
+switch(x,a = 2, y = 3)
+
+switch(x,a = 2, y = 3
+) #
+
+switch(x,a = 2, y = 3 #
 )
 
 if_else(a,