From c51f442c8c33d4d171adf6c5875cbfc7a9e1d1eb Mon Sep 17 00:00:00 2001
From: Gleb Mazovetskiy <glex.spb@gmail.com>
Date: Fri, 19 Apr 2019 10:13:53 +0100
Subject: [PATCH] Forbid empty custom property values

sass-spec: https://github.com/sass/sass-spec/pull/1385
Fixes #2655
---
 src/expand.cpp | 8 +++++++-
 src/parser.cpp | 2 +-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/expand.cpp b/src/expand.cpp
index 0a40410ed..bb1fab4ba 100644
--- a/src/expand.cpp
+++ b/src/expand.cpp
@@ -253,7 +253,13 @@ namespace Sass {
     if (value) value = value->perform(&eval);
     Block_Obj bb = ab ? operator()(ab) : NULL;
     if (!bb) {
-      if (!value || (value->is_invisible() && !d->is_important())) return 0;
+      if (!value || (value->is_invisible() && !d->is_important())) {
+        if (d->is_custom_property()) {
+          error("Custom property values may not be empty.", d->value()->pstate(), traces);
+        } else {
+          return nullptr;
+        }
+      }
     }
     Declaration* decl = SASS_MEMORY_NEW(Declaration,
                                         d->pstate(),
diff --git a/src/parser.cpp b/src/parser.cpp
index 2afd12cc3..a697d20c0 100644
--- a/src/parser.cpp
+++ b/src/parser.cpp
@@ -1859,7 +1859,7 @@ namespace Sass {
       css_error("Invalid CSS", " after ", message);
     }
 
-    if (schema->empty()) return {};
+    if (schema->empty()) error("Custom property values may not be empty.");
     return schema.detach();
   }