Fix Parse error on custom property fallback

parser.jison

@@ -3,6 +3,7 @@
 /* lexical grammar */
 %lex
 %%
+(--[0-9a-z-A-Z-]*)                     return 'CSS_CPROP';
 \s+                                    /* skip whitespace */
 "*"                                    return 'MUL';
 "/"                                    return 'DIV';
@@ -38,11 +39,12 @@
 ([0-9]+("."[0-9]*)?|"."[0-9]+)\b       return 'NUMBER';
 
 (calc)                                 return 'NESTED_CALC';
-(var\([^\)]*\))                        return 'CSS_VAR';
+(var)                                  return 'CSS_VAR';
 ([a-z]+)                               return 'PREFIX';
 
 "("                                    return 'LPAREN';
 ")"                                    return 'RPAREN';
+","                                    return 'COMMA';
 
 <<EOF>>                                return 'EOF';
 
@@ -67,8 +69,8 @@ expression
   	| math_expression MUL math_expression { $$ = { type: 'MathExpression', operator: $2, left: $1, right: $3 }; }
   	| math_expression DIV math_expression { $$ = { type: 'MathExpression', operator: $2, left: $1, right: $3 }; }
   	| LPAREN math_expression RPAREN { $$ = $2; }
-    | NESTED_CALC LPAREN math_expression RPAREN { $$ = $3; }
-    | SUB PREFIX SUB NESTED_CALC LPAREN math_expression RPAREN { $$ = $6; }
+    | NESTED_CALC LPAREN math_expression RPAREN { $$ = { type: 'Calc', value: $3 }; }
+    | SUB PREFIX SUB NESTED_CALC LPAREN math_expression RPAREN { $$ = { type: 'Calc', value: $6, prefix: $2 }; }
     | css_variable { $$ = $1; }
   	| css_value { $$ = $1; }
   	| value { $$ = $1; }
@@ -80,7 +82,8 @@ expression
   	;
 
   css_variable
-    : CSS_VAR { $$ = { type: 'CssVariable', value: $1 }; }
+    : CSS_VAR LPAREN CSS_CPROP RPAREN { $$ = { type: 'CssVariable', value: $3 }; }
+    | CSS_VAR LPAREN CSS_CPROP COMMA math_expression RPAREN { $$ = { type: 'CssVariable', value: $3, fallback: $5 }; }
     ;
 
   css_value

src/__tests__/index.js

@@ -168,6 +168,35 @@ test(
   'calc(var(--popupHeight) / 2)'
 )
 
+test(
+  'should ignore calc with css variables (7)',
+  testFixture,
+  'calc(var(--popupHeight, var(--defaultHeight, var(--height-150))) / 2)',
+  'calc(var(--popupHeight, var(--defaultHeight, var(--height-150))) / 2)'
+)
+
+test(
+  'should ignore calc with css variables (8)',
+  testFixture,
+  'calc(var(--popupHeight, var(--defaultHeight, calc(100% - 50px))) / 2)',
+  'calc(var(--popupHeight, var(--defaultHeight, calc(100% - 50px))) / 2)'
+)
+
+test(
+  'should ignore calc with css variables (9)',
+  testFixture,
+  'calc(var(--popupHeight, var(--defaultHeight, calc(100% - 50px + 25px))) / 2)',
+  'calc(var(--popupHeight, var(--defaultHeight, calc(100% - 25px))) / 2)'
+)
+
+test(
+  'should ignore calc with css variables (10)',
+  testFixture,
+  'calc(var(--popupHeight, var(--defaultHeight, 150px)) / 2)',
+  'calc(var(--popupHeight, var(--defaultHeight, 150px)) / 2)'
+)
+
+
 test(
   'should reduce calc with newline characters',
   testFixture,

src/lib/reducer.js

@@ -3,6 +3,8 @@ import convert from './convert'
 function reduce(node, precision) {
   if (node.type === "MathExpression")
     return reduceMathExpression(node, precision)
+  if (node.type === "Calc")
+    return reduce(node.value, precision)
 
   return node
 }

src/lib/stringifier.js

@@ -28,22 +28,30 @@ function stringify(node, prec) {
 
       str += " " + node.operator + " "
 
-      if (right.type === 'MathExpression' && order[op] < order[right.operator])
+      if (right.type === 'MathExpression' && order[op] < order[right.operator]) {
         str += "(" + stringify(right, prec) + ")"
-      else if (right.type === 'MathExpression' && op === "-" && ["+", "-"].includes(right.operator)) {
+      } else if (right.type === 'MathExpression' && op === "-" && ["+", "-"].includes(right.operator)) {
         // fix #52 : a-(b+c) = a-b-c
         right.operator = flip(right.operator);
         str += stringify(right, prec)
-      }
-      else
+      } else {
         str += stringify(right, prec)
+      }
 
       return str
     }
     case "Value":
       return round(node.value, prec)
     case 'CssVariable':
-      return node.value
+      if (node.fallback) {
+        return `var(${node.value}, ${stringify(node.fallback, prec, true)})`
+      }
+      return `var(${node.value})`
+    case 'Calc':
+      if (node.prefix) {
+        return `-${node.prefix}-calc(${stringify(node.value, prec)})`;
+      }
+      return `calc(${stringify(node.value, prec)})`;
     default:
       return round(node.value, prec) + node.unit
   }