From 9e0111fecccb2ca96a86204df41d001cbe2ab3ba Mon Sep 17 00:00:00 2001
From: April Arcus <ril@google.com>
Date: Tue, 19 Oct 2021 10:10:01 -0700
Subject: [PATCH] handle math.div

---
 tasks/converter/less_conversion.rb | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tasks/converter/less_conversion.rb b/tasks/converter/less_conversion.rb
index c6cd7e03de..0a7c50847a 100644
--- a/tasks/converter/less_conversion.rb
+++ b/tasks/converter/less_conversion.rb
@@ -173,6 +173,7 @@ def convert_to_scss(file)
       file   = replace_calculation_semantics(file)
       file   = replace_file_imports(file)
       file   = wrap_at_groups_with_at_root(file)
+      file   = replace_division(file)
       file
     end
 
@@ -182,6 +183,26 @@ def wrap_at_groups_with_at_root(file)
       }
     end
 
+    # The `/` operator is not supported in dart-sass 1.33+, but
+    # sassc/libass do not support its replacement, `math.div()`.
+    def replace_division(less)
+      re = /(?<!\w)\(\s*([^(]+?)\s+\/\s+([^)]+?)\s*\)/
+      return less if less !~ re
+      # In the future, we could publish a sassc compatible build to gems
+      # and a dart-sass compatible build to npm, or we could develop a
+      # dart-sass wrapper gem of the kind envisioned by DHH
+      # https://discuss.rubyonrails.org/t/transition-to-the-sass-npm-gem/76566/7
+      # For now, stick to libsass compatible output.
+      dart_sass = false
+      if dart_sass
+        # use dart-sass's math.div() global function
+        "@use \"sass:math\";\n" + less.gsub(re, 'math.div(\1, \2)')
+      else # sassc / libsass
+        # multiply by the reciprocal
+        less.gsub re { "(#{$1} * #{1 / $2.to_f})" }
+      end
+    end
+
     def sass_fn_exists(fn)
       %Q{(#{fn}("") != unquote('#{fn}("")'))}
     end