brace_linter() always allows {}/{ } (#1685)

* brace_linter() always allows {}/{ }

* NEWS

Co-authored-by: Indrajeet Patil <[email protected]>

Author: MichaelChirico

NEWS.md

@@ -17,6 +17,11 @@
 
 * `spaces_inside_linter()` allows terminal missing keyword arguments (e.g. `alist(arg = )`; #540, @MichaelChirico)
 
+* `brace_linter()` allows empty braced expression on the same line (e.g. `while (updating_condition()) { }`)
+  regardless of `allow_single_line` to match the corresponding behavior in {styler}. This is an expedient while
+  the style guide on handling this case awaits clarification: https://github.com/tidyverse/style/issues/191.
+  (#1346, @MichaelChirico)
+
 ## New and improved features
 
 * New `get_r_string()` helper to get the R-equivalent value of a string, especially useful for R-4-style raw strings.

R/brace_linter.R

@@ -57,36 +57,36 @@ brace_linter <- function(allow_single_line = FALSE) {
     },
     # double curly
     "not(
-      (@line1 = parent::expr/preceding-sibling::OP-LEFT-BRACE/@line1) or
-      (@line1 = following-sibling::expr/OP-LEFT-BRACE/@line1)
+      (@line1 = parent::expr/preceding-sibling::OP-LEFT-BRACE/@line1)
+      or (@line1 = following-sibling::expr/OP-LEFT-BRACE/@line1)
     )",
     # allow `(`, `,` and `%>%` on preceding line
     #
     # note that '{' is not supported in RHS call of base-R's native pipe (`|>`),
     # so no exception needs to be made for this operator
     "not(
       @line1 > parent::expr/preceding-sibling::*[not(self::COMMENT)][1][
-        self::OP-LEFT-PAREN or
-        self::OP-COMMA or
-        (self::SPECIAL and text() = '%>%')
+        self::OP-LEFT-PAREN
+        or self::OP-COMMA
+        or (self::SPECIAL and text() = '%>%')
       ]/@line2
     )"
   ))
 
   # TODO (AshesITR): if c_style_braces is TRUE, invert the preceding-sibling condition
   xp_open_curly <- glue::glue("//OP-LEFT-BRACE[
-    { xp_cond_open } and (
-      not(@line1 = parent::expr/preceding-sibling::*/@line2) or
-      @line1 = following-sibling::*[1][not(self::COMMENT)]/@line1
+    { xp_cond_open }
+    and (
+      not(@line1 = parent::expr/preceding-sibling::*/@line2)
+      or @line1 = following-sibling::*[1][not(self::COMMENT or self::OP-RIGHT-BRACE)]/@line1
     )
   ]")
 
   xp_open_preceding <- "parent::expr/preceding-sibling::*[1][self::OP-RIGHT-PAREN or self::ELSE or self::REPEAT]"
 
   xp_paren_brace <- glue::glue("//OP-LEFT-BRACE[
     @line1 = { xp_open_preceding }/@line1
-    and
-    @col1 = { xp_open_preceding }/@col2 + 1
+    and @col1 = { xp_open_preceding }/@col2 + 1
   ]")
 
   xp_cond_closed <- xp_and(c(
@@ -98,20 +98,22 @@ brace_linter <- function(allow_single_line = FALSE) {
     "not(
       @line1 = ancestor::expr/following-sibling::*[1][
         self::OP-COMMA or self::OP-RIGHT-BRACKET or self::OP-RIGHT-PAREN
-      ]/@line1
+      ]
+        /@line1
     )",
     # double curly
     "not(
-      (@line1 = parent::expr/following-sibling::OP-RIGHT-BRACE/@line1) or
-      (@line1 = preceding-sibling::expr/OP-RIGHT-BRACE/@line1)
+      (@line1 = parent::expr/following-sibling::OP-RIGHT-BRACE/@line1)
+      or (@line1 = preceding-sibling::expr/OP-RIGHT-BRACE/@line1)
     )"
   ))
 
   # TODO (AshesITR): if c_style_braces is TRUE, skip the not(ELSE) condition
   xp_closed_curly <- glue::glue("//OP-RIGHT-BRACE[
-    { xp_cond_closed } and (
-      (@line1 = preceding-sibling::*[1]/@line2) or
-      (@line1 = parent::expr/following-sibling::*[1][not(self::ELSE)]/@line1)
+    { xp_cond_closed }
+    and (
+      (@line1 = preceding-sibling::*[1][not(self::OP-LEFT-BRACE)]/@line2)
+      or (@line1 = parent::expr/following-sibling::*[1][not(self::ELSE)]/@line1)
     )
   ]")
 

tests/testthat/test-brace_linter.R

@@ -409,3 +409,14 @@ test_that("brace_linter lints if/else matching braces correctly", {
     linter
   )
 })
+
+# Keep up to date with https://github.com/tidyverse/style/issues/191
+test_that("empty brace expressions are always allowed inline", {
+  expect_lint("while (FALSE) {}", NULL, brace_linter())
+  expect_lint("while (FALSE) { }", NULL, brace_linter())
+  # only applies when `{` is "attached" to the preceding token on the same line
+  expect_lint("while (FALSE)\n{}", rex::rex("Opening curly braces"), brace_linter())
+  expect_lint("while (FALSE)\n{ }", rex::rex("Opening curly braces"), brace_linter())
+  expect_lint("while (FALSE) {}", NULL, brace_linter(allow_single_line = TRUE))
+  expect_lint("while (FALSE) { }", NULL, brace_linter(allow_single_line = TRUE))
+})